CN117269878A

CN117269878A - Ammeter detection method and power conversion equipment

Info

Publication number: CN117269878A
Application number: CN202311229915.5A
Authority: CN
Inventors: 赵密; 陈熙; 王雷; 黄伟
Original assignee: Ecoflow Technology Ltd
Current assignee: Ecoflow Technology Ltd
Priority date: 2023-09-21
Filing date: 2023-09-21
Publication date: 2023-12-22

Abstract

The application provides an ammeter detection method and power conversion equipment. The method can be applied to an inverter, the inverter is electrically connected with a power grid through an ammeter, and the ammeter is used for detecting real-time reactive power transmitted between the inverter and the power grid. The method comprises the following steps: when the inverter enters an ammeter detection state, the current expected reactive power of the inverter is obtained as first expected reactive power, and the first reactive power detected by the ammeter is obtained. The first desired reactive power is then adjusted to obtain a second desired reactive power, and the inverter is controlled to operate to output reactive power to the grid in accordance with the second desired reactive power. And after the detection result of the ammeter is stable, acquiring the second reactive power detected by the ammeter. And confirming the detection result of the ammeter according to the relation between the first reactive power and the second reactive power and the first expected reactive power and the second expected reactive power. The ammeter detection method can accurately and efficiently detect the wiring condition of the ammeter in real time.

Description

Ammeter detection method and power conversion equipment

Technical Field

The application relates to the technical field of power electronics, in particular to an ammeter detection method and power conversion equipment.

Background

The photovoltaic system or the optical storage system can be provided with an ammeter at the grid connection position, so that the energy transmission between the system and the power grid can be detected through the ammeter. When the spontaneous self-service mode and the anti-backflow mode are realized (namely, the photovoltaic system is forbidden to surfing the internet with residual electricity or surfing the internet with full amount), the system depends on the ammeter to realize the power dispatching and metering functions. Currently, the main current adopted ammeter is a three-phase ammeter of an external current transformer (current transformer, CT). However, the three-phase ammeter of the external CT is relatively easy to have a wiring error (for example, the CT is connected reversely or the phase sequence is connected wrongly), so that power dispatching logic errors and inaccurate metering results can occur, and abnormal situations that the photovoltaic system or the optical storage system does not supply power to the power utilization load or discharges power to the power grid can occur. And therefore requires meter wiring detection.

The main ammeter wiring detection scheme that commonly uses in the correlation technique is: the photovoltaic system or the optical storage system actively performs multiple charging and discharging according to the active power instruction, and the fact that the electric meter wiring is connected positively or in a wrong way is judged through the change difference between the actual active power detected by the electric meter and the active power instruction. However, such detection schemes have a number of limitations. For example, multiple charging and discharging may result in a loss of electricity or an increase in electricity consumption. Moreover, the detection scheme is limited by the power generation state of the photovoltaic module and/or the energy storage state of the battery pack in the system, so that the detection time is long easily, the active power is unstable, and the active power fluctuation is easily caused by the change of the power load, so that the detection failure or false detection can be caused. In addition, the scheme needs to suspend the spontaneous use mode and the anti-backflow mode of the system to execute, and cannot meet the requirement of real-time detection.

Disclosure of Invention

In view of this, the present application provides an ammeter detection method and power conversion device, which can detect the wiring condition of an ammeter in real time, efficiently and accurately, and also can not cause loss of electricity or increase of electricity consumption.

The first aspect of the present application provides an ammeter detection method, which can be applied to an inverter. The inverter is electrically connected with the power grid through an ammeter, and the ammeter is used for detecting real-time reactive power transmitted between the inverter and the power grid. The ammeter detection method comprises the following steps: when the inverter enters an ammeter detection state, the current expected reactive power of the inverter is obtained as first expected reactive power, and the first reactive power detected by the ammeter is obtained. The first desired reactive power is then adjusted to obtain a second desired reactive power, and the inverter is controlled to operate to output reactive power to the grid in accordance with the second desired reactive power. And after the detection result of the ammeter is stable, acquiring the second reactive power detected by the ammeter. And confirming the detection result of the ammeter according to the relation between the first reactive power and the second reactive power and the first expected reactive power and the second expected reactive power.

It will be appreciated that since the photovoltaic system includes both inductive electronic components (e.g., transformers, inductors) and capacitive electronic components (e.g., capacitors). After the inverter is connected with the grid, reactive power exchange can be carried out between the inverter and the grid, and active power consumption can not be caused in the process. Thus, in actual operation, the inverter will operate according to the expected reactive power to output reactive power of the expected magnitude to the grid, and accordingly, the utility meter connected between the inverter and the grid can detect the reactive power transfer between the inverter and the grid. When the wiring of the ammeter is misplaced, the reactive power detected by the ammeter is deviated from the expected reactive power due to the change of the phase sequence or the direction of the three-phase output. It can be seen that the reactive power detected by the electricity meter can reflect the wiring condition of the electricity meter. Therefore, in the electric meter detection method, when the inverter enters an electric meter detection state, the current expected reactive power of the inverter is obtained as the first expected reactive power, the first reactive power detected by the electric meter is obtained, then the first expected reactive power is adjusted to obtain the second expected reactive power, the inverter is controlled to work according to the second expected reactive power so as to output the reactive power to the power grid, after the electric meter detection result is stable, the second reactive power detected by the electric meter is obtained again, and therefore, whether the electric meter reading has deviation can be confirmed based on the relation among the first reactive power, the second reactive power, the first expected reactive power and the second expected reactive power, and then the detection result of the electric meter is confirmed.

Compared with the prior art that a spontaneous use mode and an anti-backflow mode are needed to be suspended, and the wiring condition of the ammeter is confirmed through the active power detected by the ammeter in the process of multiple charging and discharging, the ammeter detection method of the present application utilizes the change of reactive power pushed to the power grid when the inverter is connected and the reactive power detected by the ammeter corresponding to the change of reactive power to confirm the wiring condition of the ammeter, and the ammeter detection method can be suitable for various working conditions of the inverter, and is not required to be specifically applied to the charging and discharging working conditions, so that the ammeter detection method is not limited by the power generation state of the photovoltaic module and the energy storage state of the battery pack, and can realize real-time and efficient detection. Moreover, compared with active power, the photovoltaic system and the power grid have relatively stable requirements for reactive power, so that the wiring condition of the ammeter can be more accurately detected, the active power is not required to be consumed, and electric quantity loss or electric quantity increase can not be caused.

In an embodiment, after adjusting the first desired reactive power to obtain a second desired reactive power and controlling the operation of the inverter to output reactive power to the power grid according to the second desired reactive power, the method further comprises: and periodically acquiring real-time reactive power detected by the ammeter according to a preset data acquisition period in a first preset time. And taking the real-time reactive power detected by the ammeter at the starting moment as the initial reactive power, the maximum reactive power and the minimum reactive power. And in each data acquisition period, calculating a first difference value between the real-time reactive power and the initial reactive power, a second difference value between the real-time reactive power and the maximum reactive power and a third difference value between the real-time reactive power and the minimum reactive power. And when the absolute value of the first difference value, the absolute value of the second difference value and the absolute value of the third difference value are smaller than a first preset power threshold value, acquiring the real-time working time length of the inverter. And when the real-time working time length of the inverter is not longer than the first preset time, updating the maximum reactive power and the minimum reactive power according to the current real-time reactive power. And when the real-time working time of the inverter is longer than the first preset time, confirming that the detection result of the ammeter is stable.

In an embodiment, confirming the detection result of the electric meter according to the relation between the first reactive power and the second reactive power and the first expected reactive power and the second expected reactive power comprises: a first power difference between the first reactive power and the second reactive power is calculated. A second power difference is calculated for the first expected reactive power and the second expected reactive power. A third power difference between the first power difference and the second power difference is calculated. And when the absolute value of the third power difference value is smaller than the second preset power threshold value, confirming that the ammeter is connected. And when the absolute value of the third power difference value is not smaller than the second preset power threshold value, confirming that the ammeter is in misconnection.

In an embodiment, the determining the detection result of the electric meter according to the relation between the first reactive power and the second reactive power and the first expected reactive power and the second expected reactive power further includes: when the positive connection of the ammeter is confirmed, the positive connection frequency of the ammeter is increased by 1. When the misconnection of the ammeter is confirmed, the misconnection frequency of the ammeter is increased by 1. When the positive connection times of the electric meter reach a preset positive connection times threshold value, confirming that the detection result of the electric meter is positive connection and controlling the inverter to exit the electric meter detection state. When the misconnection times of the electric meter reach a preset misconnection times threshold, confirming that the electric meter detection result is misconnection and controlling the inverter to exit the electric meter detection state.

In an embodiment, the method further comprises: and when the number of the positive connection times of the electric meter does not reach the preset number of the positive connection times threshold, the number of the misconnection times of the electric meter does not reach the preset number of the misconnection times threshold, and the accumulated adjustment times of the first expected reactive power do not reach the preset total adjustment times, returning to execute the step of acquiring the current expected reactive power of the inverter as the first expected reactive power and acquiring the first reactive power detected by the electric meter.

In an embodiment, adjusting the first desired reactive power to obtain the second desired reactive power comprises: adjusting the first desired reactive power according to:

wherein the method comprises the steps of，Q _{set_1} For a first desired reactive power; q (Q) _{set_2} Is the second desired reactive power; ΔQ _set Adjusting the step length for the preset power; k (K) _{set_1} A preset first time number threshold value; k (K) _{set_2} A preset second time threshold value; k (K) _{set_3} For the preset total adjustment times, K _{set_3} ＞K _{set_2} ＞K _{set_1} The method comprises the steps of carrying out a first treatment on the surface of the k is the cumulative adjustment times of the first expected reactive power, and k is a natural number.

In an embodiment, the method further comprises: and when the positive connection times of the electric meter do not reach the preset positive connection times threshold, the misconnection times of the electric meter do not reach the preset misconnection times threshold, and the accumulated adjustment times of the first expected reactive power reach the preset total adjustment times, confirming that the detection result of the electric meter is detection failure. Wherein, the sum of the preset positive connection time threshold value and the preset error connection time threshold value is not smaller than the preset total adjustment time.

In an embodiment, after adjusting the first desired reactive power to obtain a second desired reactive power and controlling the operation of the inverter to output reactive power to the power grid according to the second desired reactive power, the method further comprises: and when at least one of the absolute value of the first difference value, the absolute value of the second difference value and the absolute value of the third difference value is not smaller than a first preset power threshold value, confirming that the detection result of the ammeter is detection failure.

In an embodiment, the method further comprises: when the detection result of the ammeter is confirmed to be misconnection, outputting first prompt information, wherein the first prompt information is used for prompting misconnection of the ammeter. And outputting second prompt information when the detection result of the ammeter is confirmed to be detection failure, wherein the second prompt information is used for prompting the ammeter to be detection failure.

A second aspect of the present application provides a power conversion apparatus comprising an inverter for electrical connection to a power grid through an electricity meter and a controller. The controller is configured to perform the electric meter detection method according to the first aspect or any one of the embodiments of the first aspect.

A third aspect of the present application provides a photovoltaic system comprising a photovoltaic module and a power conversion apparatus according to the second aspect described above.

A fourth aspect of the present application provides an electronic device, including a processor and a memory, where the memory is configured to store a program, instructions or code, and the processor is configured to execute the program, instructions or code in the memory, so as to implement the electric meter detection method according to the first aspect or any embodiment of the first aspect.

The fifth aspect of the present application provides an electric meter detection device, including a first acquisition module, a control module, a second acquisition module, and an electric meter detection module, where the first acquisition module is configured to acquire, when an inverter enters an electric meter detection state, a current expected reactive power of the inverter as a first expected reactive power and acquire a first reactive power detected by the electric meter. The control module is used for adjusting the first expected reactive power to obtain second expected reactive power and controlling the inverter to work according to the second expected reactive power so as to output reactive power to the power grid. The second acquisition module is used for acquiring second reactive power detected by the ammeter after the detection result of the ammeter is stable. The ammeter detection module is used for confirming the detection result of the ammeter according to the relation between the first reactive power and the second reactive power and the first expected reactive power and the second expected reactive power.

A sixth aspect of the present application provides a computer-readable storage medium storing a computer program loaded by a processor to perform the electric meter detection method according to the first aspect or any one of the embodiments of the first aspect.

In addition, the technical effects caused by any possible implementation manners of the second aspect to the sixth aspect may refer to the technical effects caused by different implementation manners of the first aspect, which are not described herein.

Drawings

Fig. 1A is a schematic diagram of an application scenario of an ammeter detection method provided in an embodiment of the present application.

Fig. 1B is a schematic diagram of another application scenario of the electric meter detection method provided in the embodiment of the present application.

Fig. 2A is a schematic diagram of a control principle of the inverter in fig. 1A and 1B.

Fig. 2B is a schematic diagram of the PLL in fig. 2A.

Fig. 3 is a flowchart of an ammeter detection method according to an embodiment of the present application.

Fig. 4 is another flowchart of an ammeter detection method provided in an embodiment of the present application.

Fig. 5 is another flowchart of an ammeter detection method according to an embodiment of the present application.

Fig. 6 is a detailed flow chart of the method of detecting the electricity meter shown in fig. 3.

Fig. 7 is another detailed flowchart of the electricity meter detection method shown in fig. 3.

Fig. 8A is a schematic diagram of a power conversion device according to an embodiment of the present application.

Fig. 8B is another schematic diagram of a power conversion device provided in an embodiment of the present application.

Fig. 9A is a schematic diagram of a photovoltaic system provided in an embodiment of the present application.

Fig. 9B is another schematic diagram of a photovoltaic system provided in an embodiment of the present application.

Fig. 10 is a schematic diagram of an electronic device according to an embodiment of the present application.

Fig. 11 is a schematic diagram of an ammeter detection device according to an embodiment of the present application.

Detailed Description

It should be noted that the terms "first" and "second" in the specification, claims and drawings of this application are used for distinguishing between similar objects and not for describing a particular sequential or chronological order.

It should be further noted that the method disclosed in the embodiments of the present application or the method shown in the flowchart, including one or more steps for implementing the method, may be performed in an order that the steps may be interchanged with one another, and some steps may be deleted without departing from the scope of the claims.

Some embodiments will be described below with reference to the accompanying drawings. The following embodiments and features of the embodiments may be combined with each other without conflict.

Referring to fig. 1A, a schematic connection diagram of a photovoltaic system according to an embodiment of the present application is shown. In fig. 1A, photovoltaic system 10 includes a photovoltaic module 101, a maximum power tracking (Maximum Power Point Tracking, MPPT) circuit 102, an inverter 103, and a controller 104. The output end of the photovoltaic module 101 is electrically connected to the input end of the MPPT circuit 102, the output end of the MPPT circuit 102 is electrically connected to the DC end of the inverter 103 through positive and negative DC buses (dc_bus+, dc_bus-) and the AC end of the inverter 103 is electrically connected to the power load 20 through AC buses (ac_bus+, ac_bus-). The ac end of the inverter 103 may be electrically connected to the electric meter 30 through an ac bus, and the electric meter 30 may be electrically connected to the electric grid 40 through a live wire (i.e., a phase line, L, may include an a phase line, a B phase line, and a C phase line) and a neutral line (N), so that the inverter 103 may form an electrical connection relationship with the electric grid 40, and may further be in a grid-connected operation state. The inverter 103 is also connected to the controller 104.

Based on such a design, the photovoltaic system 10 may operate in a self-service mode. Specifically, photovoltaic module 101 may be configured to convert solar energy into direct current and output the direct current to MPPT circuit 102.MPPT circuit 102 then transmits the dc power to inverter 103 via the positive and negative dc buses. The MPPT circuit 102 may be configured to perform maximum power tracking on the output power of the photovoltaic module 101, so that the maximum output power of the photovoltaic module 101 is connected to the inverter 103, thereby improving the photovoltaic utilization rate. Under the control of the controller 104, the inverter 103 may be configured to convert the direct current into an alternating current and output the alternating current to the electric load 20, so that the electric load 20 may operate electrically.

In some embodiments, referring to fig. 1B, the photovoltaic system 10 may further include a battery pack 105. The positive and negative poles (+, -) of the battery pack 105 are electrically connected to positive and negative dc buses. The battery pack 105 may also be connected to the controller 104. Thus, when the power required by the electric load 20 is smaller than the power output by the inverter 103, under the control of the controller 104, a part of the power output by the inverter 103 is used for supplying power to the electric load 20, and a part of the power is transmitted to the battery pack 105 through the positive and negative direct current buses, so that the battery pack 105 is charged and stores energy. Thus, the photovoltaic system 10 shown in fig. 1B may also be referred to as a photovoltaic energy storage system (which may be referred to as a photovoltaic energy storage system). Further, in the case where the power required by the electric load 20 is larger than the power output by the inverter 103, the battery pack 105 may supply the electric load 20 together with the inverter 103 supplying the electric load 20. Therefore, no matter what the output power of the photovoltaic module 101 is, the electricity load 20 does not need to take electricity from the power grid 40, and the photovoltaic system 10 can realize spontaneous self-use.

Of course, in the case where the power required by the electric load 20 is greater than the power output by the inverter 103, the electric grid 40 may supply the electric load 20 together with the inverter 103 supplying the electric load 20 to meet the power supply requirement of the electric load 20. In the case of a shortage of the battery pack 105, the inverter 103 may also convert the ac power of the power grid 40 into dc power and charge the battery pack 105.

The photovoltaic system 10 may also operate in a self-powered, residual electricity on-line mode where the power demand of the electrical load 20 is less than the power output by the inverter 103 and the grid 40 allows for feeding. That is, under the control of the controller 104, a portion of the power output by the inverter 103 is used to power the electrical load 20, and a portion is fed into the power grid 40.

The photovoltaic system 10 may also operate in a full-on-grid mode with the grid 40 allowing for feeding. That is, under the control of the controller 104, the power output by the inverter 103 is fed entirely into the grid 40.

In addition, the photovoltaic system 10 of fig. 1A and 1B may also operate in an anti-reverse flow mode, i.e., the photovoltaic system 10 is prohibited from remaining or full-line.

In some cases (e.g., power grid 40 is powered down or the power is not stable, etc.), inverter 103 may also be electrically disconnected from grid 40 such that inverter 103 is in an off-grid operating state to prevent damage to power load 20 and inverter 103.

It is understood that the photovoltaic module 101 may include one photovoltaic panel or include a plurality of photovoltaic panels connected in series, parallel, or series-parallel, which are not limited herein. MPPT circuit 102 may be provided independently, may be provided in a photovoltaic panel, or may be integrated with inverter 103, and is not limited herein.

In the photovoltaic system 10 shown in fig. 1A, the inverter 103 may be used to perform an inverter function (i.e., direct current to alternating current, direct Current to Alternating Current, DC-AC). In the photovoltaic system 10 shown in fig. 1B, the inverter 103 can realize not only an inversion function but also a rectification (i.e., conversion of alternating current into direct current, alternating Current to Direct Current, AC-DC) function. Accordingly, the inverter 103 in fig. 1B may also be referred to as a bi-directional converter (Power Conversion System, PCS). The circuit configuration of the inverter 103 is not limited, and the inverter 103 may be a full bridge inverter, a half bridge inverter, or the like, for example.

Furthermore, a filter circuit (e.g., LC filter circuit, see inductance L and capacitance C in fig. 2A) may be further provided at the ac end of the inverter 103. Accordingly, the power output from the inverter 103 is filtered by the filter circuit and then transmitted to the electricity meter 30. Thus, noise can be reduced, and electromagnetic interference and ammeter detection errors can be reduced. It can be appreciated that due to the ac side of the inverter 103 and the power consuming load 20 (for convenience of description, the load impedance Z is shown in fig. 2A _l Shown) are electrically connected to the ac bus, and thus are shown in fig. 2A as load impedance Z _l Is connected between the filter circuit and the electricity meter 30 for display.

It should be noted that the power transmitted between the photovoltaic system 10 and the power grid 40 includes active power and reactive power. Because the photovoltaic system 10 is connected to the power grid 40 and the power-consuming load 20, active power transmitted between the photovoltaic system 10 and the power grid 40 can be used to supply power to the power-consuming load 20, electric equipment of the power grid 40, line equivalent resistance, and the like, and thus can be consumed. Moreover, the power supply system is also very susceptible to fluctuation caused by the influence of the electric load 20, the electric equipment of the power grid 40 and the circuit. For example, adding, subtracting, or replacing the electrical load 20 may result in a larger fluctuation in active power. Under the condition that the structure of the photovoltaic system 10 is not changed, the electric load 20 is not increased, reduced or replaced, and the electric equipment is not changed by the power grid 40, the fluctuation of active power can be caused due to poor contact of a certain contact point in the electric load 20, short circuit of a circuit and the like.

Since the photovoltaic system 10 includes inductive electronic components (e.g., transformers, inductors) and capacitive electronic components (e.g., capacitors), the inductive electronic components and the capacitive electronic components may also be present in the electrical devices of the electrical loads 20 and the electrical grid 40, and therefore, the reactive power transferred between the inverter 103 and the electrical grid 40 may be used to establish a magnetic field for the inductive electronic components in the electrical devices of the photovoltaic system 10, the electrical loads 20 and the electrical grid 40, and an electric field for the capacitive electronic components in the electrical devices of the photovoltaic system 10, the electrical loads 20 and the electrical grid 40 to exchange energy. Active power is not consumed to perform work during the energy exchange process. Therefore, under the condition that the structure of the photovoltaic system 10 is not changed, the electric load 20 is not increased, reduced or replaced, and the electric equipment is not changed by the power grid 40, the integral inductive reactance and capacitive reactance are basically unchanged, so that the reactive power transmitted between the inverter 103 and the power grid 40 can be basically kept stable, and the reactive power does not cause the consumption of active power.

The battery pack 105 may include a battery cell (not shown) and a battery management system (Battery Management System, BMS, not shown), where the battery cell may be one battery cell, or may be composed of a plurality of battery cells connected in series, parallel, or series-parallel, and the positive and negative poles of the battery cell constitute the positive and negative poles (+, -) of the battery pack 105. The BMS is connected to the battery cell and the controller 104. Accordingly, the controller 104 may control the charge and discharge of the battery cells through the BMS. In some embodiments, the photovoltaic system 10 of fig. 1B may also include a direct current converter (i.e., direct Current to Direct Current, DC-DC) converter (not shown). One end of the DC converter is electrically connected with the anode and the cathode of the battery pack 105, and the other end of the DC converter is electrically connected with the anode and the cathode DC buses. The dc converter may also be connected to the controller 104 or the BMS, so that the dc power may be converted under the control of the controller 104 or the BMS, thereby adjusting the charge power or the discharge power of the battery pack 105. It will be appreciated that the circuit structure of the dc converter is not limited, and the dc converter may include any of a Boost (Boost) circuit, a Buck (Buck) circuit, and/or a Buck-Boost (Buck-Boost) circuit. Further examples, the dc converter may employ a dual active full bridge (Dual Active Bridge, DAB) converter. It is understood that the dc converter may be integrated into the battery pack 105 or may be provided separately, which is not limited herein.

The controller 104 may employ a micro control unit (Microcontroller Unit, MCU) or other control circuitry. Accordingly, the controller 104 may send an active power command, a reactive power command, or other commands to the inverter 103 such that the inverter 103 may ultimately output active power consistent with the desired active power magnitude indicated by the active power command, and output reactive power consistent with the desired reactive power magnitude indicated by the reactive power command. It is to be understood that the controller 104 may be integrated with the inverter 103, or may be separately provided from the inverter 103, which is not limited herein. The controller 104 may also communicate with the upper computer 50 wirelessly or by wire, so as to obtain an instruction (such as an ammeter detection instruction for instructing the controller 104 to perform ammeter detection) sent by the upper computer 50 and feedback information to the upper computer 50. The upper computer 50 may be a terminal device (such as a mobile phone, a tablet, a remote controller, a computer, etc.) of a user or an industrial control computer, etc.

In the present embodiment, the controller 104 may be configured to control the operation of the inverter 103 by PQ control (i.e., constant power control, see fig. 2A). Of course, other control manners may be adopted by the controller 104, and the control manners are not limited to the present application.

Specifically, as shown in fig. 2A, the controller 104 may acquire the voltage (i.e., a-phase voltage u) of each phase alternating current output from the inverter 103 to the ammeter 30 through an internal detection circuit or an external detection circuit (e.g., ammeter, power meter, power analyzer, etc.) _a B-phase voltage u _b Voltage u of C phase _c For ease of description, FIG. 2A is collectively referred to as u _abc ) And obtaining the respective phase currents flowing through the inductor L in the filter circuit (i.e., the A-phase current i flowing through the inductor L _La B-phase current i _Lb Current i of C phase _Lc For ease of description, FIG. 2A is collectively referred to as i _Labc ). The controller 104 may then convert the three-phase voltage u through a matrix transformation _abc Three-phase current i _Labc Converting into a two-phase rotation coordinate system (i.e. dq coordinate system, wherein d-axis corresponds to active power and q-axis corresponds to reactive power) to obtain d-axis voltage u _d Q-axis voltage u _q D-axis current i _Ld Current on q axis i _Lq 。

The controller 104 may be based on the detected d-axis voltage u _d Q-axis voltage u _q Performing power control with preset expected active power Pset and expected reactive power Qset to obtain d-axis current reference value i _dref And q-axis current reference value i _qref (based on the principle: power is equal to the product of voltage and current) and then based on the d-axis current reference i _dref Q-axis current reference value i _qref And the detected d-axis current i _d Current on q axis i _q The d-axis voltage reference value is obtained through a current inner loop (for example, the current inner loop can be a proportional integral regulator)Q-axis voltage reference value->

Since the inverter 103 is in the grid-connected operation state, the Phase and frequency of the voltage output by the inverter 103 need to be kept synchronous with the Phase and frequency of the voltage of the power grid 40, so in fig. 2A, the controller 104 also obtains the Phase θ of the power grid 40 through a Phase-Locked Loop (PLL). Specifically, as shown in fig. 2B, the controller 104 converts the three-phase voltage u by matrix transformation _abc Conversion to d-axis voltage u _d Q-axis voltage u _q Then to q-axis voltage u _q And a voltage reference value u _qref The difference result=0 is subjected to Proportional-Integral (PI) operation, to obtain the angular frequency adjustment amount Δw. The angular frequency adjustment quantity delta w is compared with the grid angular frequency w ₀ And summing and then carrying out Integral (I) operation to obtain the phase theta. The phase θ output by the phase-locked loop can also be fed back to the matrix transformation process, so that the controller 104 can perform matrix transformation according to the phase θ, and then obtain a new d-axis voltage u _d Q-axis voltage u _q Thereby forming a closed loop control. Where the phase θ represents the phase of the voltage output from the inverter 103. Based on the phase-locked principle, when u _q When the phase is 0, the phase locking of the phase-locked loop is successful, and the phase theta of the output of the phase-locked loop isEqual to the grid voltage phase.

Thus, the controller 104 can convert the d-axis voltage reference value according to the phase θ through matrix inversionQ-axis voltage reference value->Converting into three-phase stationary coordinate system (abc coordinate system, wherein a axis corresponds to A phase, B axis corresponds to B phase, and C axis corresponds to C phase) to obtain three-phase voltage reference value ∈ ->(i.e., A-phase voltage reference +.>B-phase voltage reference->C-phase voltage reference->)。

It will be appreciated that the matrix transformation described above is a constant amplitude transformation, and may include a Clark transformation and a Park transformation. At three-phase voltage u _abc For example, three-phase voltage u _abc Can be converted into a two-phase static coordinate system (namely an alpha beta coordinate system) through Clark conversion to obtain alpha-axis voltage u _α And beta-axis voltage u _β Then, the alpha-axis voltage u is converted by Park _α And beta-axis voltage u _β Conversion to a two-phase rotating coordinate system to obtain d-axis voltage u _d Q-axis voltage u _q . Three-phase current i _abc And three-phase voltage u _abc The same or similar, and will not be described in detail. Since the matrix inverse transformation is an inverse of the matrix transformation, in the matrix inverse transformation, the d-axis voltage reference valueQ-axis voltage referenceValue->Can be converted into a two-phase static coordinate system through Park inverse transformation and then converted into a three-phase static coordinate system through Clark inverse transformation, so that a three-phase voltage reference value +. >

Finally, the controller 104 may be based on the three-phase voltage reference valueTo generate corresponding pulse width modulation (Pulse Width Modulation, PWM) signals to the power switches in the inverter 103 to control the on-off state of the power switches so that the inverter 103 can output active power consistent with the desired active power Pset and reactive power consistent with the desired reactive power Qset to the grid 40.

It follows that by controlling the desired active power Pset, the active power finally output by the inverter 103 can be controlled, and by controlling the desired reactive power Qset, the reactive power finally output by the inverter 103 can be controlled.

It is understood that the PWM signal may be, for example, a sinusoidal pulse width modulated (Sinusoidal Pulse Width Modulation, SPWM) signal or other type of modulated signal. Since the PWM signal can control the inverter 103 to output the active power and the reactive power in accordance with the expected magnitude, the PwM signal is the active power command and the reactive power command.

The type of the electric network 40 is not limited, and may be, for example, a utility or other regional electric network, or a micro-electric network, etc. The power grid 40 may provide three-phase alternating current. The electric load 20 may be, for example, various types of ac loads in a home.

The electric meter 30 may also be referred to as an electric energy meter. The electricity meter 30 may be used to detect energy transfer between the photovoltaic system 10 and the grid 40. Moreover, when the photovoltaic system 10 is operating in the self-service mode and the anti-reverse-flow mode (i.e., no surplus electricity is allowed to be on-line or full-line), the photovoltaic system 10 relies heavily on the electricity meter 30 to perform power scheduling and metering functions.

However, in summary, no matter what mode the photovoltaic system 10 is operating in, the electric meter 30 may be configured to detect the real-time voltage and real-time current of each phase, and calculate the real-time active power and real-time reactive power, electric quantity, etc. data transmitted by the inverter 103 and the electric network 40 based on the real-time voltage and real-time electric current.

For example, when pset=100W (watts), then inverter 103 transmits active power 100W to grid 40, and, correspondingly, meter 30 may calculate active power as 100W. When pset= -100W, then the inverter 103 obtains the active power 100W from the grid 40, and correspondingly, the electric meter 30 can calculate the active power as-100W. For another example, when qset=100 Var, then inverter 103 and grid 40 exchange reactive power 100Var, and accordingly, meter 30 may calculate reactive power as 100Var. When qset= -100Var, then inverter 103 and grid 40 exchange reactive power-100 Var, and accordingly, meter 30 may calculate reactive power as-100 Var. Wherein the inductive reactive power is positive because the voltage phase angle of the inductive element leads the current phase angle of the inductive element. Since the voltage phase angle of the capacitive element lags the current phase angle of the capacitive element, the capacitive reactive power has a negative value. Thus, when the reactive power transmitted by the inverter 103 and the grid 40 is positive, it is indicated that the transmitted reactive power is inductive reactive power. When the reactive power transmitted by the inverter 103 and the grid 40 is negative, it is indicated that the reactive power transmitted is capacitive reactive power.

The electric meter 30 may be, for example, a three-phase electric meter using an external current transformer (current transformer, CT) and an external voltage transformer (potential transformer, PT). The external CT is electrically connected with the ac bus, the fire phase and the zero line, and may be used to reduce the current of each phase to a value measurable by the ammeter 30 according to a set proportion according to an electromagnetic induction principle, so that the ammeter 30 may detect the actual magnitude of the current of each phase. It will be appreciated that the current is directional, and thus the external CT for each phase of current has one current inlet terminal for the incoming current and one current outlet terminal for the outgoing current. The detection principle of the external PT is similar to that of the external CT, so that the description is omitted.

It will be appreciated that the meter 30 is provided with a dial which can be used to visually display the detected data for convenient reading by a user. The dial may be an electronic dial or a mechanical dial, and is not limited herein. In addition, the electric meter 30 may be communicatively connected to the controller 104, and transmit data such as the detected power to the controller 104. It is understood that the communication connection may be a wired communication or a wireless communication. The wired communication mode includes, but is not limited to, a serial communication mode based on an RS485 serial bus or a controller 104 local area network (Controller Area Network, CAN) bus or other parallel communication modes. Wireless communication methods include, but are not limited to, bluetooth, zigBee, ethernet, power line carrier communication methods, and the like. The controller 104 may also store data transmitted by the meter 30 in an internal memory (e.g., flash memory, etc.) or an external memory for later use.

However, the external CT meter 30 is more prone to be connected with a wiring error (e.g. CT reverse connection or phase sequence error), so that power dispatching logic errors and inaccurate metering results may occur. Since the electricity meter 30 is disposed at the ac end of the inverter 103 (i.e., at the grid-connected location), an error in the electricity meter wiring may cause the photovoltaic system 10 shown in fig. 1A or 1B to fail to supply power to the electricity load 20 or discharge electricity to the grid 40. And therefore requires meter wiring detection.

The main ammeter wiring detection scheme that commonly uses in the correlation technique is: the photovoltaic system 10 or the optical storage system actively performs multiple charging and discharging according to the active power instruction, and the wiring of the electric meter 30 is judged to be positive or wrong by the change difference between the actual active power detected by the electric meter and the active power instruction.

However, such detection schemes have a number of limitations. For example, the system takes power from the power grid 40 at each charge and discharges power generated by the photovoltaic module 101 and/or stored in the battery pack 105 to the power grid 40 at each discharge, and thus, multiple charges and discharges may result in a loss of power or an increase in power consumption. Moreover, the detection scheme is limited by the power generation state of the photovoltaic module 101 and/or the energy storage state of the battery pack 105 in the system, which easily results in overlong detection time and unstable active power. For example, when the light intensity is insufficient, the photovoltaic module 101 cannot generate power to the inverter 103, and the inverter 103 cannot output active power, and cannot perform ammeter detection. For another example, when the maximum power tracking speed of the MPPT circuit 102 is too slow, it is necessary to wait for the MPPT circuit 102 to track the maximum power, so that it is difficult for the inverter 103 to quickly and stably output enough active power, and the ammeter detection time is too long. For another example, the battery pack 105 has a charge-discharge protection function, and will not be charged after full charge, and will not be discharged below a certain amount of electricity, so it is necessary to wait until the battery pack 105 is not fully charged, and wait until the battery pack 105 is above a certain amount of electricity, and then wait until the battery pack 105 is discharged, which also prolongs the detection time. In addition, the active power fluctuation is easily caused by the change of the electric load 20, so that the active power detected by the electric meter is changed, and the change is not expected, and therefore, the detection failure or false detection can be caused.

In addition, the system can adjust output power when working in the spontaneous use mode and the anti-reflux mode, and when adopting this detection scheme, this detection scheme needs to set up fixed active power instruction, therefore, this detection scheme needs to suspend the spontaneous use mode of system and prevent the mode of backward flow and just can carry out, also can't satisfy the demand of real-time detection ammeter wiring condition.

Therefore, the embodiment of the application provides an ammeter detection method, which can detect the wiring condition of an ammeter in real time, efficiently and accurately, and cannot cause electric quantity loss or electric quantity increase.

The technical solutions of the present application are described in further detail below with reference to the accompanying drawings.

Referring to fig. 3, a flowchart of an ammeter detection method according to an embodiment of the present application is shown. It will be appreciated that in the present embodiment, the method may be applied to the inverter 103 in the photovoltaic system 10 shown in fig. 1A and 1B and executed by the controller 104 of the inverter 103. Of course, in other embodiments, the method may also be implemented by a device/electronics/controller/processor dedicated to meter detection.

Specifically, as shown in fig. 3, the electricity meter detection method includes:

step S301: when the inverter enters an ammeter detection state, the current expected reactive power of the inverter is obtained as first expected reactive power, and the first reactive power detected by the ammeter is obtained.

In the present embodiment, the expected reactive power may be set by the controller 104 according to the power demand of the power consuming load 20, the grid 40, etc. connected to the inverter 103. The desired reactive power may also be pre-stored in a memory internal to the controller 104 or in an external memory so that the controller 104 may retrieve the first desired reactive power from the memory. Of course, the first expected reactive power may also be a user-defined setting, and be sent to the controller 104 through the host computer 50, which is not limited herein.

Since the electric meter 30 can detect real-time reactive power transmitted between the inverter 103 and the grid 40, the controller 104 can obtain the first reactive power from the electric meter 30.

Step S302: and adjusting the first expected reactive power to obtain a second expected reactive power, and controlling the inverter to work according to the second expected reactive power so as to output reactive power to the power grid.

It will be appreciated that there is a set power difference between the second desired reactive power and the first desired reactive power. Therefore, the reactive power output by the inverter 103 after the adjustment is different from the reactive power output before the adjustment.

After the desired reactive power adjustment, the Qset in the reactive power command sent by the controller 104 to the inverter 103 is adjusted to the second desired reactive power to control the inverter 103 to output a corresponding amount of reactive power to the grid 40 in step S302. After the inverter 103 is controlled to operate according to the second expected reactive power, the next step may be performed after waiting a preset period of time. Such a design is mainly intended to wait for the reactive power command to take effect, so that step S303 can be performed after the reactive power starts to change, so that it can be ensured that the adjusted reactive power is obtained. It is understood that the preset time period may be set to, for example, 2s (seconds) or other time period, and the controller 104 may time the preset time period by an internal timer or an external timer.

Step S303: and after the detection result of the ammeter is stable, acquiring the second reactive power detected by the ammeter.

Because the reactive power detection result of the ammeter is unstable, false detection or detection failure can be easily caused. Therefore, in step S303, the second reactive power is obtained after the ammeter detection result is stable, in order to improve the accuracy of the detection result and the detection efficiency. Step S304: and confirming the detection result of the ammeter according to the relation between the first reactive power and the second reactive power and the first expected reactive power and the second expected reactive power.

It will be appreciated that in the case of a CT-up of the meter 30, the same change in reactive power detected by the meter 30 will occur when a change in reactive power is expected. In an ideal state, if the inverter output meets the expectation and the ammeter detects no error, the first reactive power is equal to the first expected reactive power, and the second reactive power is equal to the second expected reactive power. Considering that the inverter control has a certain fluctuation range and the electric meter detection accuracy is a problem, the power difference before and after the reactive power adjustment is expected to be reflected on the reactive power detected by the electric meter before and after the adjustment. That is, when there is a certain power difference between the first and second expected reactive powers, there is also a certain power difference between the first and second reactive powers detected by the electricity meter 30, and the power difference is identical, e.g., equal, or within an acceptable range with the power difference between the first and second expected reactive powers.

Conversely, in the case of the reverse CT connection or the phase sequence misconnection of the electric meter 30, since the abnormal condition of the electric meter being not supplied to the electric load 20 or discharged to the electric grid 40 may occur due to the electric meter wiring error, the reactive power detected by the electric meter 30 may deviate from the expected reactive power, and thus the reactive power change detected by the electric meter 30 may be different from the expected reactive power change. That is, the power difference between the first reactive power and the second non-power detected by the electricity meter may not be consistent with the power difference between the first expected reactive power and the second expected reactive power.

The reactive power detection process of the electricity meter 30 will be described.

Suppose that inverter 103 outputs an a-phase voltageB-phase voltageC-phase voltage->Phase A currentB phase current-> C-phase currentWherein U is the voltage amplitude, I is the current amplitude, w is the angular frequency, t is the time,/->Is the initial phase.

Three-phase voltage u _a 、u _b 、u _c The Clark transformation is performed to obtain a voltage vector:

wherein e ^j2π/3 、e ^-j2π/3 Are both rotation vectors, j is the imaginary part.

It can be seen that the three-phase voltage u _a 、u _b 、u _c Becomes alpha-axis voltage u _α And beta-axis voltage u _β Wherein, the method comprises the steps of, wherein,

likewise, three-phase voltage i _a 、i _b 、i _c The Clark transformation is carried out to obtain the current phasor:

Thus, three-phase current i _a 、i _b 、i _c Becomes alpha-axis current i _α And beta-axis current i _β Wherein, the method comprises the steps of, wherein,

therefore, the instantaneous reactive power Q calculated by the electric meter 30 is:

herein definition i _{a_real} 、i _{b_real} 、i _{c_real} The actual A, B, C phase current i output for the inverter 103 according to the desired setting _{a_sample} 、i _{b_sample} 、i _{c_sample} A, B, C phase current, i, detected for the electricity meter _{α_real} I is the actual alpha-axis current after Clark conversion _{α_sample} The alpha-axis current calculated for the Clark transformed electricity meter 30. i.e _{β_real} I is the actual beta-axis current after Clark conversion _{β_sample} The beta-axis current calculated for the Clark transformed electricity meter 30.

When CT of A phase is reversely connected, CT of B phase and CT of C phase are positively connected:

i _{a_sample} ＝-i _{a_real} ，i _{b_sample} ＝i _{b_real} ，i _{c_sample} ＝i _{c_real} it can be seen that the current of phase a detected by the electricity meter is opposite to the actual current of phase a.

Thus, i _{α_real} Will become:

i _{α_sample} will become:

that is, if phase A CT is reversed, i _{α_sample} ≠i _{α_real} I.e. i calculated by the electricity meter 30 _{α_sample} The error, in turn, will cause an error in the calculation of the reactive power Q of equation (3) that does not correspond to the actual reactive power. Similarly, phase B CT and phase C CT are reversed, which also results in reactive power Q calculation errors of equation (3).

When the B-phase CT and C-phase CT are wire interchanged (i.e., phase sequence error):

i _{a_sample} ＝i _{a_real} ，i _{b_sample} ＝i _{c_real} ，i _{c_sample} ＝i _{b_real} it can be seen that the B-phase current detected by the ammeter is the actual C-phase current, and the C-phase current detected by the ammeter is the actual B-phase current.

As can be seen from the combination of formula (2) and formula (3), i _{β_sample} Will become:

that is, if the phase sequence of the B-phase CT and the C-phase CT is wrong, i _βsample ≠i _{β_real} I.e. i calculated by the electricity meter 30 _βsample The error, in turn, will cause an error in the calculation of the reactive power Q of equation (3) that does not correspond to the actual reactive power. Similarly, phase a CT and phase B CT are reversed and phase a CT and phase C CT are reversed, resulting in reactive power Q calculation errors of equation (3).

It can be seen that when the electricity meter is in a wrong connection (including reverse CT connection and wrong CT phase sequence), the reactive power detected by the electricity meter 30 will not match the actual reactive power (i.e. not match the expected one), and when the electricity meter is in a correct connection, the reactive power detected by the electricity meter 30 will match the actual reactive power (i.e. match the expected one), so the reactive power detected by the electricity meter 30 may reflect that the electricity meter 30 is in a correct connection (i.e. a positive connection) or a wrong connection (i.e. a wrong connection).

Therefore, in step S304, the controller 104 may confirm the connection condition of the electric meter according to the relationship between the first reactive power and the second reactive power and the first expected reactive power and the second expected reactive power. The controller 104 may also store the results of the meter detection for later use.

In summary, in the method for detecting an electric meter according to the embodiment of the present application, when the inverter 103 enters an electric meter detection state, the current expected reactive power of the inverter 103 is obtained as the first expected reactive power and the first reactive power detected by the electric meter 30 is obtained, then the first expected reactive power is adjusted to obtain the second expected reactive power, and the inverter 103 is controlled to work according to the second expected reactive power to output the reactive power to the electric grid 40, and after the electric meter detection result is stable, the second reactive power detected by the electric meter 30 is obtained again, so that whether the readings of the electric meter 30 deviate or not can be confirmed based on the relation among the first reactive power, the second reactive power, the first expected reactive power and the second expected reactive power, and then the detection result of the electric meter is confirmed. Compared with the prior art that a spontaneous use mode and an anti-backflow mode are needed to be suspended, and the wiring condition of the ammeter is confirmed through the active power detected by the ammeter in the process of multiple charging and discharging, the method of the embodiment of the application utilizes the change of the reactive power transmitted by the power grid 40 when the inverter 103 is connected with the grid and the reactive power detected by the ammeter corresponding to the change of the reactive power, can be suitable for various working conditions of the inverter 103, does not need to be specifically applied to the charging and discharging working conditions, is not limited by the power generation state of the photovoltaic module 101 and the energy storage state of the battery pack 105, and can realize real-time and efficient detection. That is, even in the case where the photovoltaic module 101 cannot generate power, the battery pack 105 is fully charged or the electric quantity is discharged, the MPPT circuit 102 is too slow in tracking speed, and the photovoltaic system 10 is in the self-service mode or the anti-reverse-flow mode, the method of the embodiment of the present application can be executed in real time, and thus the detection duration is more controllable. Moreover, compared with active power, the photovoltaic system 10 and the power grid 40 have relatively stable requirements for reactive power, so that the wiring condition of the electric meter can be more accurately detected, active power is not required to be consumed, electric quantity loss or electric quantity increase can not be caused, and the electricity consumption experience of a user can not be influenced.

In the embodiment of the present application, the inverter 103 may confirm whether to enter the electric meter detection state according to a set triggering condition, where the triggering condition may be set correspondingly according to an actual situation, and is not limited herein.

For example, in one embodiment, after the photovoltaic system 10 is powered on, the controller 104 is communicatively connected to the host computer 50, and the host computer 50 may send the electric meter detection command set by the user or preset to the controller 104. The meter detection instructions are used to control the controller 104 to execute meter detection logic. Further, the controller 104 may control the inverter 103 to enter the electricity meter detection state according to the electricity meter detection command transmitted from the host computer 50. Of course, the controller 104 may control the inverter 103 to enter the ammeter detection state according to the last detection result. Alternatively, the controller 104 may control the inverter 103 to enter the meter detection state by combining the meter detection command and the last detection result.

For further example, referring to fig. 4, before step S301, the electric meter detection method according to the embodiment of the present application may include:

step S401: and receiving an ammeter detection instruction sent by the upper computer.

Step S402: and confirming whether the ammeter detection instruction indicates to actively detect the operation state of the ammeter.

It is understood that the operation state of the electricity meter 30 may include a communication state, a connection state, etc. of the electricity meter 30.

The meter detection command may indicate that the operation state of the meter 30 is actively detected by setting an active detection signal. The active detection signal may be a flag bit, a character, a data packet, etc., which is not limited herein, and may be set by a user performing a related operation on the upper computer 50. For example, when the meter detection command includes an active detection signal, the meter detection command indicates that the operation state of the meter 30 is actively detected. When the meter detection command does not include the active detection signal, it indicates that the meter detection command does not indicate the operation state of the active detection meter 30.

Step S403: and if the ammeter detection instruction indicates to actively detect the operation state of the ammeter, determining whether the inverter is electrically connected with the ammeter and whether the ammeter is in a normal communication state.

The manner in which the controller 104 detects whether the inverter 103 is electrically connected to the electricity meter 30 and whether the electricity meter 30 is in a normal communication state is not limited. For example, the controller 104 may detect whether or not there is ac power having a phase or frequency matching the voltage of the power grid 40 on the ac bus by an internal detection circuit or an external detection circuit, and if there is ac power having a phase or frequency matching the voltage of the power grid 40, it may be determined that the inverter 103 is electrically connected to the electricity meter 30. And vice versa, it can be determined that the inverter 103 is not electrically connected to the electric meter 30. Further, when detecting that the inverter 103 is electrically connected to the electric meter 30, the controller 104 may also generate and store a corresponding electric meter connection signal (may be a flag bit, a character, a data packet, etc.) to indicate that the inverter 103 is electrically connected to the electric meter 30, and then may directly determine the electrical connection condition of the inverter 103 and the electric meter 30 according to the electric meter connection signal. For another example, the controller 104 may send a request to the meter 30 to read meter detection data, and if the meter 30 responds to the request, it may confirm that the meter 30 is in a normal communication state. If the meter 30 does not respond to the request, it can be confirmed that the meter 30 is in an abnormal communication state.

Step S404: when the inverter is electrically connected with the electric meter and the electric meter is in a normal communication state, the inverter is controlled to enter the electric meter detection state in response to the electric meter detection instruction.

Step S405: and when the inverter is not electrically connected with the ammeter or the ammeter is in an abnormal communication state, the ammeter detection instruction is not responded.

It will be appreciated that since the electricity meter 30 can normally detect real-time reactive power and also transmit the detected real-time reactive power to the controller 104 in a case where the inverter 103 is electrically connected to the electricity meter 30 and the electricity meter 30 is in a normal communication state, the controller 104 can normally perform electricity meter detection. Therefore, the controller 104 may control the inverter 103 to enter the electricity meter detection state in response to the electricity meter detection instruction in step S403. Since the real-time reactive power cannot be normally detected by the ammeter 30 in the case where the inverter 103 is not electrically connected to the ammeter 30, the ammeter 30 cannot transmit the detected real-time reactive power to the controller 104 in the case where the ammeter 30 is in an abnormal communication state, and thus the controller 104 cannot perform ammeter detection. Therefore, the controller 104 does not respond to the electricity meter detection command in step S404, and thus does not control the inverter 103 to enter the electricity meter detection state. Based on such design, the reliability and efficiency of ammeter detection can be improved.

Step S406: and if the ammeter detection instruction does not indicate to actively detect the operation state of the ammeter, acquiring the last detection result of the ammeter.

The controller 104 may obtain the last detection result of the ammeter 30 from an internal memory or an external memory.

Step S407: and when the last detection result is that the ammeter is misconnected or the ammeter detection fails, responding to an ammeter detection instruction, and controlling the inverter to enter an ammeter detection state.

In this way, the ammeter test may be performed again to verify whether the last test result is correct.

In addition, since the last detection result is that the ammeter is misconnected or the ammeter fails to be detected, it means that the ammeter 30 cannot detect the actual reactive power in the last detection process, and corresponding measures need to be taken to enable the ammeter 30 to be normally detected. However, it is not known whether the electric meter 30 can normally detect before the current detection starts, so in step S407, when the last detection result is that the electric meter is misconnected or the electric meter detection fails, the current detection needs to be entered to confirm whether the current electric meter 30 can detect the actual reactive power.

Step S408: and when the last detection result is positive connection, the ammeter detection instruction is not responded.

It will be appreciated that when the last detection result is positive connection, it indicates that the electricity meter 30 is wired normally, and the detection result is actual reactive power, so that the electricity meter can be used normally, so that no time is wasted to detect the electricity meter wiring condition. Therefore, the controller 104 does not respond to the electricity meter detection command in step S408.

Based on the design, the detection efficiency can be improved, and the reliability of the ammeter in use can also be improved.

In this embodiment of the present application, since the first expected reactive power is adjusted in step S302, and the inverter 103 is controlled to operate according to the adjusted second expected reactive power, the reactive power output by the inverter 103 to the power grid 40 will fluctuate, the real-time reactive power detected by the electric meter 30 will also fluctuate, and when the fluctuation is large, the real variation amplitude of the reactive power before and after adjustment will be difficult to be presented, so that the detection result of the electric meter will be inaccurate easily. Therefore, after step S302, the method according to the embodiment of the present application further confirms whether the detection result of the ammeter is stable. Specifically, referring to fig. 5, the confirmation process may include the steps of:

step S501: and periodically acquiring real-time reactive power detected by the ammeter according to a preset data acquisition period in a first preset time.

The first preset time may include a plurality of data acquisition periods. The duration of the first preset time, the duration of the data acquisition period and the number of the data acquisition periods can be set correspondingly according to actual conditions, and the method is not limited herein. The first preset time period may be set to, for example, 10s (seconds). To ensure that the inverter 103 is able to fully receive the data detected by the meter, the duration of the data acquisition cycle is greater than the duration of the communication between the meter 30 and the controller 104. For example, when the communication duration required for the ammeter 30 to transmit the detection data to the controller 104 is 180ms (milliseconds), the data acquisition period may be set to 200ms.

Step S502: and taking the real-time reactive power detected by the ammeter at the starting moment as the initial reactive power, the maximum reactive power and the minimum reactive power.

Step S503: and in each data acquisition period, calculating a first difference value between the real-time reactive power and the initial reactive power, a second difference value between the real-time reactive power and the maximum reactive power and a third difference value between the real-time reactive power and the minimum reactive power.

Step S504: and confirming whether the absolute value of the first difference value, the absolute value of the second difference value and the absolute value of the third difference value are smaller than a first preset power threshold value.

It is understood that the absolute value of the first difference, the absolute value of the second difference, and the absolute value of the third difference may represent the fluctuation of the real-time reactive power detected by the electric meter 30. If the absolute value of the first difference value, the absolute value of the second difference value and the absolute value of the third difference value are smaller than the first preset power threshold value, the detected real-time reactive power is smaller in change amplitude, and therefore the detected real-time reactive power is stable. If at least one of the absolute value of the first difference value, the absolute value of the second difference value and the absolute value of the third difference value is not smaller than the first preset power threshold value, the detected real-time reactive power is larger in change amplitude, and therefore the detected real-time reactive power is unstable.

The first preset power threshold is not limited, and may be, for example, a product of the second expected reactive power and a preset ratio, where the preset ratio may be set according to an actual situation. For example, when the second desired reactive power is 250Var, the preset ratio is set to 1/5, i.e. the first preset power threshold is 50Var.

Step S505: and when the absolute value of the first difference value, the absolute value of the second difference value and the absolute value of the third difference value are smaller than a first preset power threshold value, acquiring the real-time working time length of the inverter.

As can be appreciated, the real-time operation duration of the inverter 103 refers to an accumulated operation duration calculated when the inverter 103 starts to operate according to the second expected reactive power (i.e. the reactive power output by the inverter 103 starts to change), and the controller 104 may count the real-time operation duration through an internal timer or an external timer.

Step S506: and when the real-time working time length of the inverter is not longer than the first preset time, updating the maximum reactive power and the minimum reactive power according to the current real-time reactive power.

That is, if the current real-time reactive power is greater than the previously detected maximum reactive power, the current real-time reactive power is taken as the latest maximum reactive power. And if the current real-time reactive power is smaller than the minimum reactive power detected previously, taking the current real-time reactive power as the latest minimum reactive power. Accordingly, the absolute value of the first difference, the absolute value of the second difference and the absolute value of the third difference can be updated in real time, so that the fluctuation condition of the real-time reactive power detected by the ammeter 30 can be more accurately confirmed.

Step S507: and when the real-time working time of the inverter is longer than the first preset time, confirming that the detection result of the ammeter is stable.

Step S508: and when at least one of the absolute value of the first difference value, the absolute value of the second difference value and the absolute value of the third difference value is not smaller than a first preset power threshold value, confirming that the detection result of the ammeter is detection failure.

Therefore, by setting the first preset power threshold, the method of the embodiment of the application can preliminarily confirm the fluctuation condition of the real-time reactive power detected by the electric meter 30, and if the real-time reactive power detected by the electric meter 30 is preliminarily confirmed to be stable, the first preset time is observed, and the detection result of the electric meter can be confirmed to be stable under the condition that the real-time reactive power detected by the electric meter 30 is small in variation amplitude in the first preset time. The second reactive power error in this case is small and available. Thus, the accuracy and the reliability of confirming the stable condition of the detection result of the ammeter can be improved. Otherwise, if the preliminary confirmation of the larger variation amplitude of the real-time reactive power detected by the ammeter 30 or the larger variation amplitude of the real-time reactive power detected at a certain moment in the first preset time, the unstable detection result of the ammeter can be confirmed, and the error of the detection result of the ammeter is caused by the existence of the excessive error of the second reactive power, so that the detection result of the ammeter is the detection failure.

Further, the method of the embodiment of the application can further comprise:

when the failure of the electric meter detection is confirmed, the inverter can be controlled to exit the electric meter detection state, and after waiting for a second preset time, the inverter is controlled to enter the electric meter detection state again.

That is, when confirming that the ammeter detection fails, the controller 104 may start to suspend the detection for a second preset time at a time when confirming that the ammeter detection fails, so as to provide the inverter 103 with a sufficient buffer time, so that the variation amplitude of the reactive power output by the inverter 103 may be weakened and the ammeter detection may be re-performed after tending to be stable. Thus, the success rate and the efficiency of ammeter detection can be improved. The second preset time may be set according to practical situations, for example, may be set to 30min (minutes), and the second preset time may be counted by an internal timer or an external timer of the controller 104.

When it is determined that the detection result of the electricity meter is stable, electricity meter detection may be continued. That is, the step of acquiring the second reactive power detected by the electricity meter (i.e., step S303) may be performed next at this time.

Further, referring to fig. 6, in step S304, the electric meter detection result may be obtained through steps S604 to S608 in fig. 6. It is understood that, in fig. 6, step S601 may refer to step S301 in fig. 3, step S602 may refer to step S302 in fig. 3, and step S603 may refer to step S303 in fig. 3, so that the description will not be repeated here.

Steps S604 to S608 are described below.

Step S604: calculating a first power difference value between the first reactive power and the second reactive power; a second power difference is calculated for the first expected reactive power and the second expected reactive power.

Wherein the first power difference value may be used to characterize the magnitude of change in reactive power detected by the electricity meter. The second power difference may be used to characterize the magnitude of the change in the expected reactive power of the inverter 103.

Step S605: a third power difference between the first power difference and the second power difference is calculated.

Wherein the third power difference value may be used to characterize a difference between a magnitude of change in reactive power detected by the electric meter and a magnitude of change in expected reactive power of the inverter 103.

Step S606: and confirming whether the absolute value of the third power difference value is smaller than a second preset power threshold value.

The second preset power threshold may be set correspondingly according to the actual situation, and may be the same as or similar to the first preset power threshold, for example.

Step S607: and when the absolute value of the third power difference value is smaller than the second preset power threshold value, confirming that the ammeter is connected.

Step S608: and when the absolute value of the third power difference value is not smaller than the second preset power threshold value, confirming that the ammeter is in misconnection.

It can be seen that by setting the second preset power threshold, the method in the embodiment of the present application can determine whether the variation amplitude of the reactive power detected by the electric meter is too different from the variation amplitude of the expected reactive power of the inverter 103. If the absolute value of the third power difference is smaller than the second preset power threshold, it indicates that the variation amplitude of the reactive power detected by the electric meter is not much different from the variation amplitude of the expected reactive power of the inverter 103, and the variation amplitude is considered as consistent. Therefore, the variation amplitude of the reactive power detected by the ammeter 30 accords with the expected amplitude, and the ammeter 30 can realize true and accurate detection, so that the ammeter can be confirmed to be connected positively at the moment. If the absolute value of the third power difference is not smaller than the second preset power threshold, it indicates that the variation amplitude of the reactive power detected by the electric meter is larger than the variation amplitude of the expected reactive power of the inverter 103. Therefore, the variation amplitude of the reactive power detected by the ammeter 30 is inconsistent with the expected value, and the ammeter 30 cannot realize true and accurate detection, so that the misconnection of the ammeter can be confirmed at the moment.

It will be appreciated that, since the positive or wrong connection of the electric meter has been confirmed in steps S607 and S608, the controller 104 may also control the inverter 103 to exit the electric meter detection state, and stop the detection.

Of course, in some embodiments, to further ensure that the detection result of the electric meter is correct, the step S302 may be performed multiple times to adjust the first reactive power multiple times for the situation that the electric meter is being connected, and then the third power difference may be calculated multiple times in the step S304 to perform multiple times of confirmation.

Specifically, referring to fig. 7, in step S304, the electricity meter detection result may be obtained through steps S704 to S707b, S708a, S709a, S710a in fig. 7. It is understood that, in fig. 7, step S701 may refer to step S301 in fig. 3, step S702 may refer to step S302 in fig. 3, and step S703 may refer to step S303 in fig. 3, so that the description will not be repeated here. Step S704 to step S706 refer to step S604 to step S606 in fig. 6, step S707a is step S607 in fig. 6, step S707b refers to step S608 in fig. 6, and further description is omitted herein.

Steps S708a, S709a, S710a are described below.

Step S708a: when the positive connection of the ammeter is confirmed, the positive connection frequency of the ammeter is increased by 1.

It is understood that the controller 104 may count the number of meter counts by an internal counter or an external counter.

Step S709a: and confirming whether the positive connection times of the ammeter reach a preset positive connection times threshold value.

It is understood that the preset number of positive connection threshold may be set according to practical situations, and is not limited herein, and may be set to 2, for example.

Step S710a: when the positive connection times of the electric meter reach a preset positive connection times threshold value, confirming that the detection result of the electric meter is positive connection and controlling the inverter to exit the electric meter detection state.

In step S710a, a counter or a timer used in the foregoing steps may be cleared.

Similarly, in step S304, a plurality of acknowledgements may be performed for the case of misconnection of the electric meter. Therefore, with continued reference to fig. 7, step S304 in fig. 3 may further include steps S708b, S709b, S710b in fig. 7.

Step S708b: when the misconnection of the ammeter is confirmed, the misconnection frequency of the ammeter is increased by 1.

Similar to the count of meter misconnections, the controller 104 may also count meter misconnections by other counters internal or external.

Step S709b: and confirming whether the misconnection times of the ammeter reach a preset misconnection times threshold value.

It is understood that the preset misconnection number threshold may be set according to practical situations, and is not limited herein, and may be set to 4, for example.

Step S710b: when the misconnection times of the electric meter reach a preset misconnection times threshold, confirming that the electric meter detection result is misconnection and controlling the inverter to exit the electric meter detection state.

In step S710a, a counter or a timer used in the foregoing steps may be cleared. The next time the meter is put into the meter detection state, the meter can be re-detected, re-timed and counted.

In addition, referring to fig. 7 again, for the case that the number of positive connection times of the electric meter does not reach the preset number of positive connection times threshold, the step S304 may further include:

step S711: and when the positive connection times of the electric meter do not reach the preset positive connection times threshold, or the misconnection times of the electric meter do not reach the preset misconnection times threshold, confirming whether the accumulated adjustment times of the first expected reactive power reach the preset total adjustment times.

Wherein, the sum of the preset positive connection time threshold value and the preset error connection time threshold value is not smaller than the preset total adjustment time. For example, when the preset positive connection number threshold is set to 2 times and the preset misconnection number threshold is set to 4 times, the total number of adjustments may be set to be less than or equal to 6, for example, specifically set to 4 times. Of course, the total adjustment times can be set to other times according to actual conditions, as long as the total adjustment times are not larger than the sum of the preset positive connection times threshold value and the preset wrong connection times threshold value.

Step S712: when the number of positive connection times of the electric meter does not reach the preset number of positive connection times threshold, the number of misconnection times of the electric meter does not reach the preset number of misconnection times threshold, and the accumulated adjustment times of the first expected reactive power does not reach the preset total adjustment times, the step of obtaining the current expected reactive power of the inverter as the first expected reactive power and the step of obtaining the first reactive power detected by the electric meter is performed (i.e. the step of returning to the step S701 is performed).

Step S713: and when the positive connection times of the electric meter do not reach the preset positive connection times threshold, the misconnection times of the electric meter do not reach the preset misconnection times threshold, and the accumulated adjustment times of the first expected reactive power reach the preset total adjustment times, confirming that the detection result of the electric meter is detection failure.

It will be appreciated that, in normal circumstances, each time the first expected reactive power is adjusted, the steps S703-S707 b are performed to obtain whether the electric meter 30 is connected correctly or in error. Because the total adjustment frequency is smaller than or equal to the sum of the preset positive connection frequency threshold value and the preset misconnection frequency threshold value, when the accumulated adjustment frequency of the first expected reactive power reaches the preset total adjustment frequency, the situation that the positive connection frequency of the ammeter reaches the preset positive connection frequency threshold value or the misconnection frequency of the ammeter reaches the preset misconnection frequency threshold value can occur. However, if the number of positive connection times of the ammeter does not reach the preset number of positive connection times threshold, and the number of misconnection times of the ammeter does not reach the preset number of misconnection times threshold, it is indicated that there is some time or some time of ammeter detection result that the positive connection or misconnection cannot be confirmed, that is, the detection fails. Therefore, in step S713, it is possible to directly confirm that the ammeter detection result is a detection failure.

In summary, the method according to the embodiment of the present application can recognize that the electric meter 30 is connected in a positive or misconnection manner, and also recognize whether the electric meter detection fails through steps S701 to S713. Therefore, the ammeter detection result of the ammeter detection method is finer and more accurate, and false detection caused by ammeter detection failure can be avoided, so that the ammeter detection result of the ammeter detection method is more accurate and reliable.

In an embodiment of the present application, the method for detecting an electric meter may further include:

and generating an ammeter positive connection signal when the detection result of the ammeter is positive connection. The meter positive connection signal can be used for indicating that the detection result of the meter is positive connection.

And generating an ammeter misconnection signal when the detection result of the ammeter is confirmed to be misconnection. The electric meter misconnection signal can be used for indicating that the detection result of the electric meter is misconnection.

And generating an ammeter detection failure signal when the detection result of the ammeter is confirmed to be detection failure. The ammeter detection failure signal can be used for indicating that the detection result of the ammeter is detection failure.

It is to be understood that the positive connection signal, the misconnection signal and the failure detection signal of the electric meter may be flag bits, characters, data packets, etc., which are not limited in this application.

The controller 104 may store the meter positive connection signal, the meter false connection signal, or the meter detection failure signal generated by each meter detection. Thus, the controller 104 can learn the last meter detection result according to the meter positive connection signal, the meter wrong connection signal or the meter detection failure signal generated by the last meter detection after the last meter detection is completed, so as to determine whether the meter detection state should be entered again. For example, if the last meter detection generates a meter misconnection signal or a meter detection failure signal, it is determined that the meter detection state needs to be entered again. If the last ammeter detection generates an ammeter positive connection signal, judging that the ammeter detection state does not need to be entered again.

Further, in an embodiment of the present application, the method for detecting an electric meter may further include:

when the detection result of the ammeter is confirmed to be misconnection, outputting first prompt information, wherein the first prompt information is used for prompting misconnection of the ammeter.

And outputting second prompt information when the detection result of the ammeter is confirmed to be detection failure, wherein the second prompt information is used for prompting the ammeter to be detection failure.

It will be appreciated that in some embodiments, the inverter 103 or other devices in the photovoltaic system 10 may be provided with a display screen, and the controller 104 may output the prompt to the display screen to visually display the first prompt and the second prompt. In other embodiments, the controller 104 may also output the first prompt information and the second prompt information to the host computer 50 through wireless communication. Thus, the user or related personnel can know the condition of the ammeter 30 conveniently, so that the ammeter 30 can be overhauled in time.

In addition, in the process of executing step S302 multiple times to adjust the first active power multiple times, the direction of each adjustment may be the same (i.e., each adjustment is to increase the first active power or decrease the first active power), or may be different. The amplitude of each adjustment may be the same or different, and the application is not limited.

For example, the first expected reactive power may be adjusted in step S302 according to the following formula (7):

wherein Q is _{set_1} For a first desired reactive power; q (Q) _{set_2} Is the second desired reactive power; ΔQ _set Adjusting the step length for the preset power; k (K) _{set_1} A preset first time number threshold value; k (K) _{set_2} A preset second time threshold value; k (K) _{set_3} For the preset total adjustment times, K _{set_3} ＞K _{set_2} ＞K _{set_1} The method comprises the steps of carrying out a first treatment on the surface of the k is the cumulative adjustment times of the first expected reactive power, and k is a natural number.

Understandably, Δq _set 、K _{set_1} 、K _{set_2} 、K _{set_3} And k can be set correspondingly according to actual conditions. For example, in one embodiment, Δq _set May be set to 50Var. K (K) _{set_1} Can be set to 1, K _{set_2} It may be set to 2 and,may be set to 3. Further, the following formula (8) can be obtained:

thus, at the first adjustment time Q _{set_2} Can be increased toAt the second adjustment Q _{set_2} Can be reduced to->At the third adjustment Q _{set_2} Can be reduced to +.>At the fourth adjustment Q _{set_2} Can be increased toIt can be seen that based on equation (8), the second expected reactive power can be changed in a different direction and with the same magnitude (both 50 Var) after each adjustment. In this way, it is possible to substantially avoid affecting the original output of the inverter 103, and avoid that the second expected reactive power is continuously increased and is excessively large or continuously decreased and is excessively small due to the same adjustment direction, so that the deviation between the adjusted reactive power and the original reactive power of the inverter 103 is too large, thereby affecting the normal operation of the power load 20 and the like connected to the inverter 103. In addition, it is possible to prevent different detection errors due to different variation amplitudes.

It should be noted that, for simplicity of description, the foregoing method embodiments are all described as a series of acts, but it should be understood by those skilled in the art that the present application is not limited by the order of acts described, as some steps may be performed in other orders or concurrently in accordance with the present application.

Referring to fig. 8A, a schematic diagram of a power conversion apparatus according to an embodiment of the present application is shown.

As shown in fig. 8A, the power conversion device 100 may include an inverter 103, a controller 104, a photovoltaic interface 105, a grid-tie interface 107, and a load interface 106. The inverter 103 is electrically connected with the controller 104, the photovoltaic interface 105, the grid-connected interface 107 and the load interface 106, the photovoltaic interface 105 is used for electrically connecting the output end of the photovoltaic module 101, the grid-connected interface 107 is used for electrically connecting the electric meter 30 with the electric grid 40, and the load interface 106 is used for electrically connecting the electric load 20. In this way, inverter 103 can be electrically connected to electricity meter 30 and grid 40 via grid-connected interface 107. The controller 104 may be configured to control the inverter 103 to perform grid-connected operation or off-grid operation, and to control the inverter 103 to take power from the photovoltaic module 101, perform power conversion, and output the power to the power load 20, so as to supply power to the power load 20.

It will be appreciated that in the power converter apparatus 100 shown in fig. 8A, an MPPT circuit may be provided within the inverter 103, or the photovoltaic module 101 may be connected to the photovoltaic interface 105 via an apparatus configured with an MPPT circuit.

In addition, referring to fig. 8B, the power conversion apparatus 100 may further include a battery interface 108, the battery interface 108 being electrically connected with the inverter 103 and for electrically connecting the battery pack 105. Based on such a design, the controller 104 may be configured to control the inverter 103 to charge the battery pack 105 after taking power from the photovoltaic module 101 and/or the power grid 40, or to control the inverter 103 to take power from the battery pack 105 and perform power conversion to supply power to the power load 20. The controller 104 may also be connected to and communicate with the battery pack 105, the electricity meter 30, and the host computer 50 (see fig. 1A and 1B).

It will be appreciated that the photovoltaic system 10 and the inverter 103, the controller 104, the photovoltaic module 101, the battery pack 105, the electricity meter 30, the power grid 40, and the electrical load 20 may be referred to in the relevant description of fig. 1A and 1B, and will not be repeated here.

However, in summary, in both fig. 8A and 8B, the controller 104 may perform the aforementioned meter detection method to obtain the wiring detection result of the meter 30.

Referring to fig. 9A, a schematic diagram of a photovoltaic system according to an embodiment of the present application is shown.

As shown in fig. 9A, the photovoltaic system 10 may include a photovoltaic module 101 and a power conversion apparatus 100. The power conversion device 100 may be the power conversion device 100 in fig. 8A, wherein the photovoltaic interface 105 in the power conversion device 100 is connected to the photovoltaic module 101.

Of course, referring to fig. 9B, the photovoltaic system 10 may also include a battery pack 105. Correspondingly, the power conversion device 100 may be the power conversion device 100 in fig. 8B, wherein the battery interface 108 in the power conversion device 100 is connected with the battery pack 105.

Referring to fig. 10, a schematic diagram of an electronic device provided in an embodiment of the present application is shown.

As shown in fig. 10, the electronic device 60 may include a processor 601 and a memory 602.

The processor 601 may be a central processing unit (central processing unit, CPU), but may also be other general purpose processors, digital signal processors (digital signal processor, DSP), application specific integrated circuits (application specific integrated circuit, ASIC), field programmable gate arrays (field programmable gate array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or the like. A general purpose processor may be a microprocessor or any conventional processor or the like.

The Memory 602 may be, but is not limited to, a read-Only Memory (ROM) or other type of static storage device that can store static information and instructions, a random access Memory (random access Memory, RAM) or other type of dynamic storage device that can store information and instructions, an electrically erasable programmable read-Only Memory (Electrically Erasable Programmable Read-Only Memory, EEPROM), a compact disc read-Only Memory (Compact Disc Read-Only Memory) or other optical disk storage, a compact disc storage (including compact disc, laser disc, optical disc, digital versatile disc, blu-ray disc, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. The memory 602 may be stand alone and may be coupled to the processor 601 via a bus. The memory 602 may also be integral with the processor 601.

The memory 602 is used for storing programs, instructions or codes for executing the above electric meter detection method. The processor 601 is operative to execute programs, instructions or code stored in the memory 602. The memory 602 stores programs, instructions or codes that may perform some or all of the steps of the electricity meter detection method in the embodiments shown in fig. 3 to 7.

Referring to fig. 11, a schematic diagram of an ammeter detection device according to an embodiment of the present application is shown. The electricity meter detection device 70 may be used to implement the electricity meter detection method described above.

As shown in fig. 11, the electricity meter detection device 70 includes a first acquisition module 701, a control module 702, a second acquisition module 703, and an electricity meter detection module 704. The first acquisition module 701, the control module 702, the second acquisition module 703 and the electric meter detection module 704 are sequentially connected, and the first acquisition module 701 is also connected with the electric meter detection module 704.

The first obtaining module 701 is configured to obtain, when the inverter enters an ammeter detection state, a current expected reactive power of the inverter as a first expected reactive power and obtain a first reactive power detected by the ammeter.

The control module 702 is configured to adjust the first desired reactive power to obtain a second desired reactive power, and to control the operation of the inverter to output reactive power to the power grid according to the second desired reactive power.

The second obtaining module 703 is configured to obtain a second reactive power detected by the electric meter after the detection result of the electric meter is stable.

The ammeter detection module 704 is configured to confirm the detection result of the ammeter according to the relationship between the first reactive power and the second reactive power and the first expected reactive power and the second expected reactive power.

It will be appreciated that the above-described division of the various modules in the meter detection device 70 is for illustration only, and in other embodiments, the meter detection device 70 may be divided into different modules as desired to perform all or part of the functions of the meter detection device 70.

The specific implementation of each module in the embodiments of the present application may also correspond to the corresponding descriptions of the embodiments of the electric meter detection method shown in fig. 3 to 7, so that the detailed descriptions thereof will not be repeated herein.

The functional modules in the embodiments of the present application may be all integrated into one processing module/unit, or each module may be separately used as one module, or two or more modules may be integrated into one module; the integrated modules may be implemented in hardware or in hardware plus software functional modules.

The integrated modules described above may also be stored in a computer readable storage medium if implemented as software functional modules and sold or used as a stand-alone product. Based on such understanding, the technical solutions of the embodiments of the present application may be essentially or partly contributing to the prior art, and the computer software product may be stored in a storage medium, and include several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: a removable storage device, ROM, RAM, magnetic or optical disk, or other medium capable of storing program code.

The embodiments of the present application also provide a computer readable storage medium for storing a computer program or code, which when loaded and executed by a processor, implements the steps of the above-described embodiments of the method for detecting an electric meter, for example, fig. 3 to 7. Computer-readable storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules or other data. The specific embodiment of the computer readable storage medium can be referred to as the memory 602 in fig. 10, and will not be described again here.

Finally, it should be noted that the above embodiments are merely for illustrating the technical solution of the present application and not for limiting, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present application may be modified or substituted without departing from the spirit and scope of the technical solution of the present application.

Claims

1. The ammeter detection method is applied to an inverter, the inverter is electrically connected with a power grid through an ammeter, and the ammeter is used for detecting real-time reactive power transmitted between the inverter and the power grid; the ammeter detection method is characterized by comprising the following steps:

When the inverter enters an ammeter detection state, acquiring current expected reactive power of the inverter as first expected reactive power and acquiring first reactive power detected by the ammeter;

adjusting the first expected reactive power to obtain second expected reactive power, and controlling the inverter to work according to the second expected reactive power so as to output reactive power to a power grid;

after the detection result of the ammeter is stable, obtaining a second reactive power detected by the ammeter;

and confirming the detection result of the ammeter according to the relation between the first reactive power and the second reactive power and the first expected reactive power and the second expected reactive power.

2. The method of meter detection of claim 1 wherein after the adjusting the first desired reactive power to a second desired reactive power and controlling operation of the inverter to output reactive power to a power grid based on the second desired reactive power, the method further comprises:

periodically acquiring real-time reactive power detected by the ammeter according to a preset data acquisition period in a first preset time;

taking the real-time reactive power detected by the ammeter at the starting moment as initial reactive power, maximum reactive power and minimum reactive power;

Calculating a first difference value between the real-time reactive power and the initial reactive power, a second difference value between the real-time reactive power and the maximum reactive power, and a third difference value between the real-time reactive power and the minimum reactive power in each data acquisition period;

acquiring real-time working time length of the inverter when the absolute value of the first difference value, the absolute value of the second difference value and the absolute value of the third difference value are smaller than a first preset power threshold value;

when the real-time working time length of the inverter is not longer than the first preset time, updating the maximum reactive power and the minimum reactive power according to the current real-time reactive power;

and when the real-time working time of the inverter is longer than the first preset time, confirming that the detection result of the ammeter is stable.

3. The method of claim 1, wherein the determining the detection result of the electric meter according to the relationship between the first reactive power and the second reactive power and the first expected reactive power and the second expected reactive power comprises:

calculating a first power difference between the first reactive power and the second reactive power;

Calculating a second power difference of the first expected reactive power and the second expected reactive power;

calculating a third power difference between the first power difference and the second power difference;

when the absolute value of the third power difference value is smaller than a second preset power threshold value, confirming that the ammeter is connected positively;

and when the absolute value of the third power difference value is not smaller than the second preset power threshold value, confirming that the ammeter is in misconnection.

4. A method of meter testing as defined in claim 3, wherein said validating the test result of said meter based on the relationship between said first reactive power, said second reactive power, and said first expected reactive power, said second expected reactive power, further comprises:

when the positive connection of the ammeter is confirmed, adding 1 to the positive connection times of the ammeter;

when the electric meter misconnection is confirmed, adding 1 to the electric meter misconnection times;

when the positive connection times of the electric meter reach a preset positive connection times threshold value, confirming that the electric meter detection result is positive connection and controlling the inverter to exit an electric meter detection state;

when the misconnection times of the electric meter reach a preset misconnection times threshold, confirming that the electric meter detection result is misconnection and controlling the inverter to exit an electric meter detection state.

5. The electricity meter detection method of claim 4, further comprising:

and when the number of positive connection times of the electric meter does not reach the preset number of positive connection times threshold, the number of misconnection times of the electric meter does not reach the preset number of misconnection times threshold, and the accumulated adjustment times of the first expected reactive power do not reach the preset total adjustment times, returning to execute the step of acquiring the current expected reactive power of the inverter as the first expected reactive power and acquiring the first reactive power detected by the electric meter.

6. A meter test method as in claim 1 or 4, wherein said adjusting said first desired reactive power to obtain a second desired reactive power comprises:

adjusting the first desired reactive power according to:

wherein Q is _{set_1} For the first desired reactive power; q (Q) _{set_2} For the second desired reactive power; ΔQ _set Adjusting the step length for the preset power; k (K) _{set_1} A preset first time number threshold value; k (K) _{set_2} A preset second time threshold value; k (K) _{set_3} For the preset total adjustment times, K _{set_3} >K _{set_2} >K _{set_1} The method comprises the steps of carrying out a first treatment on the surface of the k is the accumulated adjustment times of the first expected reactive power, and k is a natural number.

7. The electricity meter detection method of claim 4, further comprising:

When the electric meter positive connection times do not reach a preset positive connection times threshold, the electric meter misconnection times do not reach a preset misconnection times threshold, and the accumulated adjustment times of the first expected reactive power reach a preset total adjustment times, confirming that the electric meter detection result is detection failure;

the sum of the preset positive connection time threshold and the preset misconnection time threshold is not smaller than the preset total adjustment time.

8. The method of meter detection of claim 2 wherein after the adjusting the first desired reactive power to a second desired reactive power and controlling operation of the inverter to output reactive power to a power grid based on the second desired reactive power, the method further comprises:

and when at least one of the absolute value of the first difference value, the absolute value of the second difference value and the absolute value of the third difference value is not smaller than the first preset power threshold value, confirming that the detection result of the ammeter is detection failure.

9. The electricity meter detection method of claim 1, further comprising:

outputting first prompt information when the detection result of the ammeter is confirmed to be misconnection, wherein the first prompt information is used for prompting misconnection of the ammeter;

And outputting second prompt information when the detection result of the ammeter is confirmed to be detection failure, wherein the second prompt information is used for prompting that the ammeter fails to detect.

10. A power conversion apparatus comprising an inverter for electrical connection to a power grid through an electricity meter and a controller; the controller is configured to perform the electricity meter detection method according to any one of claims 1 to 9.