CN110943486B - Control method for grid-connected and grid-disconnected seamless switching of energy storage inverter - Google Patents
Control method for grid-connected and grid-disconnected seamless switching of energy storage inverter Download PDFInfo
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Abstract
The invention discloses a control method for grid-connected and grid-disconnected seamless switching of an energy storage inverter, which comprises the steps of calculating instantaneous active power and reactive power through an inverter output voltage module value, and components of D and Q axes of the inverter output voltage module value and current in a synchronous rotating coordinate system; simulating the droop characteristic of the power grid, and setting the output voltage of a reactive power loop with droop reactive power and voltage amplitude and the frequency of an active power loop with droop active power and frequency; after passing through the voltage and current dual-loop controller, the obtained synthetic reference voltage is subjected to SVPWM wave generation to enable the output voltage of the inverter to have the same droop characteristic as the power grid voltage. The control method can realize bidirectional seamless switching between grid connection and grid disconnection, the loop structure of the controller is kept unchanged before and after switching, the output voltage can keep continuity at the switching moment and can stably continue to operate under the off-grid condition, and seamless switching is achieved. Meanwhile, the power grid fault can be judged rapidly and accurately.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a control method for grid-connected and grid-disconnected switching of an energy storage inverter.
Background
In a traditional energy storage inverter control method, in a grid-connected mode, an inverter adopts current mode control and is used as a current source to control the magnitude of input and output power; in the off-grid mode, the inverter is controlled in voltage mode to serve as a voltage source to provide an alternating voltage with stable frequency and amplitude to the load. Switching between these two modes necessarily results in transient surges and oscillations, especially more severe at on-load switching, causing the switching to fail.
Chinese patent CN 106655255A discloses a grid-connected/disconnected and grid-connected switching method and circuit for a photovoltaic energy storage inverter, which strictly limits the start-stop time of a PCS and the action time sequence of each switch in a switching circuit, and ensures the safety and reliability of switching between a grid-connected mode and a grid-disconnected mode. However, in the switching process of the method, the PCS must be stopped and restarted, and the power supply of the load cannot be continuous.
Chinese patent CN 104319815A discloses a grid-connected/off-grid seamless switching method for a microgrid converter, which judges the power grid abnormality and switches the control mode by judging the difference between the load voltage and the rated voltage. The method has the advantages that the switching of a current mode control mode and a voltage mode control mode exists, the continuity and the stability of the switching process cannot be guaranteed, meanwhile, whether the power grid fails or not is judged only through a voltage difference value and unreliable, in addition, the method can only be switched from grid connection to grid disconnection, and the switching from grid disconnection to grid connection cannot be carried out under the condition that the load is guaranteed to be continuously supplied with power.
Chinese patent CN 104795827A discloses a switching circuit of an energy storage inverter and a grid-connected/off-grid switching method and device thereof, the method only introduces a grid-connected/off-grid switching circuit but does not introduce a control mode of the inverter in a grid-connected/off-grid state, even if the switching energy of a filter circuit keeps the stability of voltage at the moment of grid-connected/off-grid switching to improve the filter performance, it is unknown whether the stable operation can be performed after switching.
Therefore, it is necessary to provide an effective method for bi-directionally and seamlessly switching between on-grid and off-grid of inverters, so as to solve the above problems.
Disclosure of Invention
The invention aims to solve the defects of the prior art and provides a control method capable of realizing bidirectional seamless switching between grid-connected and grid-disconnected, wherein the output voltage can keep continuity at the switching moment and can stably continue to operate under the off-grid condition, so that the effect of seamless switching is achieved.
Furthermore, the invention also provides a detection method for judging the power grid fault, amplitude deviation, frequency deviation and power countercurrent judgment are combined, and the power grid fault can be judged rapidly and accurately.
In order to solve the technical scheme, the invention adopts the following technical scheme:
a control method for seamless switching of grid-connected and grid-disconnected of an energy storage inverter is characterized by comprising the following steps:
s101, clark conversion and Park conversion are carried out on the output voltages Ua, ub and Uc of the inverter and the currents Ia, ib and Ic to obtain a module value Vm of the output voltage of the inverter; calculating components Vd and Vq of the output voltage modulus Vm of the inverter on the D axis and the Q axis in a synchronous rotation coordinate system, and components Id and Iq of the current on the D axis and the Q axis in the synchronous rotation coordinate system;
s102, calculating instantaneous active power P = Vd + Vq + Iq and reactive power Q = Vd + Iq + Vq by components Vd, vq, id and Iq under a synchronous rotating coordinate system;
s103, simulating the droop characteristic of the power grid, and setting reactive power ring output voltage Vm-ref with droop reactive power and voltage amplitude; simulating the drooping characteristic of a power grid, and setting the active power loop frequency f-ref of active power and frequency drooping;
s104, setting the reactive power loop output voltage Vm-ref as a given voltage module value Vref, taking the difference between the given voltage module value Vref and the inverter output voltage module value Vm as the input of a proportional-integral PI controller, obtaining a module value V required by the synthesized reference voltage through the PI controller, and obtaining an angle theta required by the synthesized reference voltage after integrating the frequency f-ref output by an active power loop;
s105, obtaining a synthetic reference voltage according to the modulus V and the angle theta, and enabling the output voltage of the inverter to have the same droop characteristic as the power grid voltage by means of SVPWM wave generation after the synthetic reference voltage passes through the voltage and current dual-loop controller;
s106, the inverter is operated in a grid-connected mode in a droop characteristic voltage source mode, or the inverter is operated in an off-grid mode in the droop characteristic voltage source mode; or switching from off-grid to grid-connection is realized.
Further, in step S103, an active power loop frequency f-ref = fn-m (P-Pn) of the active power and the frequency droop is set; wherein f-ref is the active power loop output frequency, fn is the inverter output voltage rated frequency, pn is the inverter rated active power, and m is the frequency droop coefficient.
Further, in step S103, a reactive power loop output voltage Vm-ref = Vref = Vn-n (Q-Qn) with reactive power and voltage amplitude droop is set, where Vn is an inverter grid voltage rating, qn is an inverter rated reactive power, and n is an amplitude droop coefficient.
Further, in step S106, the inverter performs grid-connected operation in a droop characteristic voltage source mode, sets an amplitude droop coefficient m and a frequency droop coefficient n, and controls the inverter to operate according to an active power given value Pn and a reactive power given value Qn; or the inverter operates in a droop characteristic voltage source mode off-grid mode, the active power Pn and the reactive power Qn are set to be 0, and the voltage with the magnitude of Vref and the frequency of f-ref is output according to the magnitude of the load active power and the reactive power according to the set droop characteristic curves of P-f and Q-V.
Further, in step S106, when the inverter operates in the droop characteristic voltage source mode in the grid-connected mode, vq is equal to Vgq; vq is a Q-axis component of the output voltage modulus Vm of the inverter under a synchronous rotating coordinate system; and Vgq is a Q-axis component of the grid voltage modulus Vgm in a synchronous rotating coordinate system.
Further, in step S106, when the inverter operates in a droop characteristic voltage source mode in a grid-connected mode, and a power grid fails, an output voltage of the inverter supports a local load and an external grid load, a frequency and an amplitude of a current output voltage of the inverter deviate from a rated voltage Vn and a rated frequency fn respectively, so as to form an inverter amplitude difference Δ V and an inverter frequency difference Δ f; when the amplitude difference delta V of the inverter and the frequency difference delta f of the inverter reach preset values, the power grid fault is judged, the switch S is immediately disconnected to cut off the external grid load, qn and Pn are set to be 0, the inverter continues to continuously supply power to the local load in the off-grid operation in the droop characteristic voltage source mode, and the smooth and seamless switching from grid connection to the off-grid operation is achieved.
Further, in step S106, when the inverter operates in a droop characteristic voltage source mode in a grid-connected mode, if the calculated instantaneous power is a positive value, the power grid transmits electric energy to the local load and the inverter; when the grid-connected switch S is still in a closed moment when the power grid fails, due to the existence of the external grid load, the inverter outputs power for the external grid load, the instantaneous power is calculated to be a negative value, the power grid can be judged to have a fault, the grid-connected switch S is immediately disconnected to cut off the external grid load, qn and Pn are set to be 0, the input current of the local load is switched from the current of the power grid to the current of the inverter, the inverter continues to continuously supply power for the local load in a grid-connected smooth seamless mode, and the grid-connected smooth seamless mode is switched to the grid-connected mode.
Further, in step S106, the inverter operates in a droop characteristic voltage source mode off-grid mode, when the grid-connected switch S is turned off, a Q-axis component Vq of the output voltage of the inverter in the synchronous rotation coordinate system is not equal to a Q-axis component Vgq of the grid voltage in the synchronous rotation coordinate system, and a difference between the Vgq and the Vq is used as an input of the phase compensation loop proportional integral PI controller.
Further, in step S106, when the inverter operates in the droop characteristic voltage source mode off-grid mode, after the power grid recovers to normal, the inverter performs power grid amplitude and phase pre-synchronization, vref is switched to a power grid voltage mode value Vm-grid as an input, and the output voltage amplitude of the inverter is adjusted to be equal to the power grid voltage amplitude; the output frequency f-ref of the active power loop and the output value fc of the frequency compensation loop PI controller are used as the input of integral, and the phase angle of the phase angle synchronous grid voltage of the output voltage of the inverter is adjusted; when the amplitude of the output voltage of the inverter is equal to the amplitude of the voltage of the power grid, after the phase angles are synchronous, the switch S is closed, meanwhile, the Vref input is recovered to Vm-ref, the phase angle compensation value fc is set to 0, the switching from grid connection to grid connection is completed, the input current of the local load is switched to the current of the power grid from the current of the inverter, the minimization of instantaneous impact current of the grid connection is realized, and the smooth seamless switching from the grid connection to the grid connection operation is realized.
Compared with the existing grid-connected and off-grid switching method, the invention has the outstanding effects that:
the inverter realizes the operation in the grid-connected state and the grid-disconnected state in the same droop characteristic voltage source mode, so that the control loop structure of the inverter is kept unchanged at the moment of switching from grid connection to grid disconnection, the output voltage can keep continuity at the moment of switching and can stably continue to operate under the grid disconnection, and the effect of seamless switching from grid connection to grid disconnection is achieved.
The inverter realizes the operation in grid-connected and off-grid states by the same droop characteristic voltage source mode, the inverter does not need to be switched from the voltage source mode to the current source mode and then started in the off-grid to grid-connected process, only the amplitude and the phase angle of the power grid are added as compensation, the output voltage of the inverter is adjusted to be equal to the voltage of the power grid in magnitude and phase synchronization, and then the grid-connected switch is closed, so that the seamless switching to the grid-connected mode operation can be realized.
In addition, various detection methods for judging the power grid faults are provided, amplitude deviation, frequency deviation and power backflow judgment schemes are provided, and the power grid faults can be judged rapidly and accurately by combined use.
Drawings
Fig. 1 is a flow chart of a control method for grid-connected and grid-disconnected seamless switching of an energy storage inverter according to the present invention.
Fig. 2 is a schematic block diagram of a grid-connected and grid-disconnected seamless switching system in the control method for grid-connected and grid-disconnected seamless switching of the energy storage inverter.
FIG. 3 is a waveform diagram of an experiment for realizing grid-connected seamless switching off-grid operation test by using the method of the present invention.
FIG. 4 is a waveform diagram of an experiment for implementing off-grid seamless switching grid-connected operation test by using the method of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The control method for the grid-connected and grid-disconnected seamless switching of the energy storage inverter, which is implemented according to the invention, as shown in fig. 1 and 2, comprises the following steps:
the output voltages Ua, ub and Uc of the inverter and the currents Ia, ib and Ic are subjected to Clark conversion and Park conversion to obtain a modulus Vm of the output voltage, and components Vd and Vq of the modulus Vm of the output voltage on a D axis and a Q axis under a synchronous rotation coordinate system are respectively obtained; and the components Id, iq of the D, Q axes of the current under the synchronous rotation coordinate;
calculating instantaneous active power P = Vd + Vq + Iq and reactive power Q = Vd + Iq + Vq by Vd, vq, id and Iq under a synchronous rotating coordinate system;
simulating the drooping characteristic of the power grid, and setting a reactive power loop with drooping reactive power and voltage amplitude: vref = Vn-n (Q-Qn); vm-ref is the magnitude of the reactive power loop output voltage, vn is the inverter rated voltage value which is the same as the grid voltage rating, qn is the inverter output rated reactive power, and n is the amplitude droop coefficient.
Simulating the droop characteristic of the power grid, and setting an active power loop with active power and frequency droop: f-ref = fn-m (P-Pn); f-ref is the active power loop output frequency, fn is the inverter output voltage rated frequency which is the same as the grid frequency value, pn is the inverter output rated active power, and m is the frequency droop coefficient.
And the magnitude Vm-ref of the output voltage of the reactive power loop is used as the difference between a given voltage modulus Vref and the modulus Vm of the output voltage of the inverter as the input of the PI controller, and the modulus V required by the synthesized reference voltage is output.
The frequency f-ref output by the power loop is integrated to obtain the angle theta required for synthesizing the reference voltage.
The reference voltage synthesized by the modulus value V and the angle theta passes through the voltage and current dual-loop controller and then is subjected to SVPWM wave generation to enable the output voltage of the inverter to have the same droop characteristic as the power grid voltage.
The inverter is operated in a droop characteristic voltage source mode in a grid-connected mode, and the active power P and the reactive power Q of the inverter are controlled to operate according to given values Pn and Qn by setting droop coefficients m and n.
The inverter operates in a droop characteristic voltage source mode off-grid mode, active power Pn and reactive power Qn are set to be 0, and voltage with the magnitude of Vref and the frequency of f-ref is output according to the magnitude of load active power and reactive power and the set droop characteristics of P-f and Q-V.
When the grid-connected operation is carried out in the droop characteristic voltage source mode, the Vq value of the Q axis component of the output voltage of the inverter in the synchronous rotating coordinate system is equal to the Vgq value of the Q axis component of the grid voltage in the synchronous rotating coordinate system.
When the grid-connected operation is carried out in the following vertical characteristic voltage source mode, when a power grid has a fault, the output voltage of the inverter supports a local load and an external grid load, the frequency and the amplitude of the voltage deviate from rated values Vn, fn is delta V, and delta f, when the deviation value delta V and delta f of the voltage amplitude and the frequency reaches a preset value, the power grid fault is judged, the switch S is immediately disconnected to cut off the external grid load, qn and Pn are set to be 0, the inverter continues to continuously supply power to the local load in the following vertical characteristic voltage source mode and the grid-disconnected operation is carried out, and the grid-connected smooth seamless switching operation is achieved.
When the grid-connected operation is carried out in the following vertical characteristic voltage source mode, the instantaneous power calculated by the anti-reflux module is a positive value, the power grid transmits electric energy to the local load and the inverter, when the grid-connected switch S is in a closed moment when the power grid fails, the inverter outputs power for the external grid load due to the existence of the external grid load, the anti-reflux module calculates that the instantaneous power is a negative value, the power grid can be judged to have a failure, the grid-connected switch S is immediately disconnected to cut off the external grid load, qn and Pn are set to be 0, the input current of the local load is switched into the inverter current from the grid current, and the inverter continues to continuously supply power for the local load in the following vertical characteristic voltage source mode, so that the grid-connected operation is smoothly and seamlessly switched to the off-network operation.
When the grid-connected switch S is disconnected during off-grid operation in the following vertical characteristic voltage source mode, the Vq value of the Q-axis component of the inverter output voltage in the synchronous rotating coordinate system is not equal to the Vgq value of the Q-axis component of the grid voltage in the synchronous rotating coordinate system, and the difference value of the Vgq and the Vq is used as the input of the phase compensation loop PI regulator.
When the grid is operated in a droop characteristic voltage source mode in an off-grid mode, after a power grid is recovered to be normal, the inverter executes pre-synchronization of the amplitude value and the phase of the power grid, vref is switched to a power grid voltage module value Vm-grid to be used as input, and the amplitude value of the output voltage of the inverter is adjusted to be equal to the amplitude value of the power grid voltage; the output frequency f-ref of the active power loop and the output value fc of the frequency compensation loop PI regulator are used as the input of integration, and the phase angle of the phase angle synchronous grid voltage of the output voltage of the inverter is regulated. And after the amplitude of the output voltage of the inverter is equal to the amplitude of the voltage of the power grid and the phase angle is synchronous, closing the switch S, simultaneously recovering the Vref input to Vm-ref, setting the phase angle compensation value fc to be 0, completing the switching from grid-off to grid-on, switching the input current of the local load from the current of the inverter to the current of the power grid, realizing the minimization of instantaneous impact current of grid-connection, and achieving the smooth and seamless switching from grid-off to grid-connection operation.
FIG. 3 is a waveform diagram of an experiment for realizing grid-connected seamless switching off-grid operation test by using the method of the present invention. Wherein, the 1 channel No. 1 is in sine shape firstly and then is in almost horizontal waveform, namely the voltage of the power grid; 2, the channel 2 is in sine wave shape and is the output voltage of the inverter; the No. 3 channel is approximately flat and then presents a sine wave shape, and the output current of the inverter is output; the 4 channel and 4 channel waveforms are the current of the power grid, which is firstly sinusoidal and then nearly straight. Therefore, the output voltage can keep continuity at the switching moment and can stably continue to operate under the off-grid condition, and the effect of seamless switching from grid connection to off-grid is achieved.
FIG. 4 is a waveform diagram of an off-grid seamless switching grid-connected operation test experiment implemented by the method of the present invention. The voltage waveform of the 1 channel 1 power grid is almost consistent with the voltage waveform of the 2 channel 2 inverter, the 3 channel 3 waveform is the output current of the inverter, and the 4 channel 4 waveform is the power grid current; the inverter can operate in a grid-connected state and an off-grid state in the same droop characteristic voltage source mode, the inverter does not need to be switched from a voltage source mode to a current source mode to be started in the process of switching off the grid to the grid, only the amplitude and the phase angle of the power grid are added for compensation, the output voltage of the inverter and the voltage of the power grid are adjusted to keep equal phase synchronization, and then the grid-connected switch is closed, so that the seamless switching to the grid-connected mode can be performed.
It should be noted that, according to implementation requirements, each step/component described in the present application can be divided into more steps/components, and two or more steps/components or partial operations of the steps/components can also be combined into a new step/component to achieve the purpose of the present invention.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (9)
1. A control method for seamless switching between grid connection and grid disconnection of an energy storage inverter is characterized by comprising the following steps:
s101, clark conversion and Park conversion are carried out on the output voltages Ua, ub and Uc of the inverter and the currents Ia, ib and Ic to obtain a module value Vm of the output voltage of the inverter; calculating components Vd and Vq of the output voltage modulus Vm of the inverter on the D axis and the Q axis in a synchronous rotation coordinate system and components Id and Iq of the current on the D axis and the Q axis in the synchronous rotation coordinate system;
s102, calculating instantaneous active power P = Vd + Vq + Iq and reactive power Q = Vd + Iq + Vq by components Vd, vq, id and Iq under a synchronous rotating coordinate system;
s103, simulating the droop characteristic of the power grid, and setting reactive power ring output voltage Vm-ref with droop reactive power and voltage amplitude; simulating the droop characteristic of the power grid, and setting the active power loop frequency f-ref of active power and frequency droop;
s104, setting the reactive power loop output voltage Vm-ref as a given voltage module value Vref, taking the difference between the given voltage module value Vref and the inverter output voltage module value Vm as the input of a proportional-integral PI controller, obtaining a module value V required by the synthesized reference voltage through the PI controller, and obtaining an angle theta required by the synthesized reference voltage after integrating the frequency f-ref output by the active power loop;
s105, obtaining a synthetic reference voltage according to the modulus V and the angle theta, and enabling the output voltage of the inverter to have the same droop characteristic as the power grid voltage by means of SVPWM wave generation after the synthetic reference voltage passes through the voltage and current double-loop controller;
s106, the inverter is operated in a grid-connected mode with a droop characteristic voltage source, or the inverter is operated in an off-grid mode with the droop characteristic voltage source; or switching from off-grid to grid-connection is realized.
2. The method according to claim 1, wherein in step S103, an active power loop frequency f-ref = fn-m (P-Pn) of active power and frequency droop is set; wherein f-ref is the active power loop output frequency, fn is the inverter output voltage rated frequency, pn is the inverter rated active power, and m is the frequency droop coefficient.
3. The method of claim 1, wherein in step S103, a reactive power loop output voltage Vm-ref = Vref = Vn-n (Q-Qn) with reactive power and voltage amplitude droop is set, where Vn is an inverter grid voltage rating, qn is an inverter rated reactive power, and n is an amplitude droop coefficient.
4. The method for controlling the energy storage inverter to switch between grid-connected state and grid-disconnected state and seamlessly switching between grid-connected state and grid-connected state according to claim 1, wherein in the step S106, the inverter is operated in a grid-connected state in a droop characteristic voltage source mode, an amplitude droop coefficient m and a frequency droop coefficient n are set, and the active power P and the reactive power Q of the inverter are controlled to operate according to an active power given value Pn and a reactive power given value Qn; or the inverter operates in a droop characteristic voltage source mode off-grid mode, the active power Pn and the reactive power Qn are set to be 0, and the voltage with the magnitude of Vref and the frequency of f-ref is output according to the magnitude of the load active power and the reactive power according to the set droop characteristic curves of P-f and Q-V.
5. The method according to claim 1, wherein Vq is equal to Vgq when the inverter operates in a droop characteristic voltage source mode during grid-connected operation in the step S106; vq is a Q-axis component of the output voltage modulus Vm of the inverter under a synchronous rotating coordinate system; and Vgq is a Q-axis component of the grid voltage modulus Vgm in a synchronous rotating coordinate system.
6. The method according to claim 1, wherein in step S106, when the inverter operates in a droop characteristic voltage source mode, and a power grid fails, the output voltage of the inverter supports a local load and an external grid load, and the frequency and amplitude of the current output voltage of the inverter deviate from a rated voltage Vn and a rated frequency fn respectively to form an inverter amplitude difference Δ V and an inverter frequency difference Δ f; when the amplitude difference delta V of the inverter and the frequency difference delta f of the inverter reach preset values, the power grid fault is judged, the switch S is immediately disconnected to cut off the external grid load, qn and Pn are set to be 0, the inverter continues to continuously supply power to the local load in the off-grid operation in the droop characteristic voltage source mode, and the smooth and seamless switching from grid connection to the off-grid operation is achieved.
7. The method according to claim 1, wherein in step S106, when the inverter operates in a droop characteristic voltage source mode during grid connection, if the calculated instantaneous power is a positive value, the grid transmits electric energy to the local load and the inverter; when the grid-connected switch S is still in a closed moment when the power grid fails, due to the existence of the external grid load, the inverter outputs power for the external grid load, the instantaneous power is calculated to be a negative value, the power grid can be judged to have a fault, the grid-connected switch S is immediately disconnected to cut off the external grid load, qn and Pn are set to be 0, the input current of the local load is switched from the current of the power grid to the current of the inverter, the inverter continues to continuously supply power for the local load in a grid-connected smooth seamless mode, and the grid-connected smooth seamless mode is switched to the grid-connected mode.
8. The method according to claim 1, wherein in step S106, the inverter operates in a droop characteristic voltage source mode, when the grid-connected switch S is turned off, a Q-axis component Vq of an output voltage of the inverter in the synchronous rotation coordinate system is not equal to a Q-axis component Vgq of a grid voltage in the synchronous rotation coordinate system, and a difference between the Vgq and the Vq is used as an input of the proportional integral PI controller of the phase compensation loop.
9. The method according to claim 1, wherein in step S106, when the inverter operates off-grid in a droop characteristic voltage source mode, and the grid returns to normal, the inverter performs grid amplitude and phase pre-synchronization, vref switches to a grid voltage modulus Vm-grid as an input, and adjusts an inverter output voltage amplitude to be equal to the grid voltage amplitude; the output frequency f-ref of the active power loop and the output value fc of the frequency compensation loop PI controller are used as the input of integral, and the phase angle of the phase angle synchronous grid voltage of the output voltage of the inverter is adjusted; when the amplitude of the output voltage of the inverter is equal to the amplitude of the voltage of the power grid, after the phase angles are synchronous, the switch S is closed, meanwhile, the Vref input is recovered to Vm-ref, the phase angle compensation value fc is set to 0, the switching from grid connection to grid connection is completed, the input current of the local load is switched to the current of the power grid from the current of the inverter, the minimization of instantaneous impact current of the grid connection is realized, and the smooth seamless switching from the grid connection to the grid connection operation is realized.
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| CN112366744B (en) * | 2020-08-14 | 2022-09-02 | 中国电力科学研究院有限公司 | Inverter seamless switching control method and device |
| CN112383055B (en) * | 2020-11-24 | 2022-12-09 | 珠海格力电器股份有限公司 | Grid-connected and off-grid scheduling method and device and energy storage air conditioning system |
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