CN114710053A

CN114710053A - Inverter, power supply system and protection method for DC side of inverter

Info

Publication number: CN114710053A
Application number: CN202210627367.0A
Authority: CN
Inventors: 李乐
Original assignee: Sungrow Power Supply Co Ltd
Current assignee: Sungrow Power Supply Co Ltd
Priority date: 2022-06-06
Filing date: 2022-06-06
Publication date: 2022-07-05
Anticipated expiration: 2042-06-06
Also published as: CN114710053B

Abstract

The application discloses a protection method for an inverter, a power supply system and a direct current side of the inverter, which comprises the following steps: the device comprises a controller, an inverter DCAC circuit, a filter circuit and a controllable switch module; each controllable switch module comprises at least one controllable switch tube; the filter circuit at least comprises a group of capacitors; the number of the controllable switch modules is the same as the number of phases of the output end of the inverter DCAC circuit; the output end of the inverter DCAC circuit is connected with the input end of the filter circuit; the output ends of at least one group of capacitors in the filter circuit are connected with corresponding controllable switch modules; and the controller is used for controlling the controllable switch module to be switched off when the shutdown instruction is received. And at the moment, the controllable switch module is turned off to enable the controllable switch module to be in a high-resistance state, so that the impact of short-circuit current is restrained by utilizing the high-resistance state of the controllable switch module, and a switch tube in the inverter DCAC circuit is protected.

Description

Inverter, power supply system and protection method for DC side of inverter

Technical Field

The application relates to the technical field of new energy power generation, in particular to an inverter, a power supply system and a protection method for a direct current side of the inverter.

Background

At present, when a short-circuit fault occurs on an alternating current side, a single-stage inverter can turn off a switching tube within microsecond time under the choking action of an inductor, so that the purpose of protecting equipment is achieved. However, when the dc side of the inverter is short-circuited, the switching tube antiparallel diode forms a rectifying circuit, and at this time, only the ac side overcurrent and short-circuit protection devices such as fuses and circuit breakers can be used for protection. The common switch tube has poor tolerance capability and can only bear microsecond short circuit impact generally, and the action time of the protection device is millisecond, so that the protection device can not protect the switch tube in the inverter, the switch tube is rapidly failed, even open fire is caused, and large current impact can be caused to a power grid.

At present, in order to avoid an external short circuit of a dc interface in the prior art, there are two methods, the first is to connect a diode in series at a dc input end of an inverter, and referring to fig. 1, the diode is reversely cut off when the external short circuit occurs, so as to protect a switching tube of the inverter. The second type is a two-stage topology, referring to fig. 2, that is, a one-stage dc/dc circuit is connected to the input terminal of the inverter, the DCDC circuit includes an inductor Ldc, a switching tube Cdc and a diode D1, and the DCDC circuit suppresses short-circuit current to realize a fast protection function. When a short circuit occurs on the direct current side of the inverter, a shutdown instruction is triggered, however, the two shutdown instructions triggered based on short circuit protection cannot effectively protect the inverter, especially the problem of short circuit of a direct current bus.

Disclosure of Invention

In view of this, embodiments of the present application provide an inverter, a power supply system, and a method for protecting a dc side of the inverter, which can perform shutdown protection in time when the inverter needs to be shutdown.

The present application provides an inverter, comprising: the device comprises a controller, an inverter DCAC circuit, a filter circuit and a controllable switch module; each controllable switch module comprises at least one controllable switch tube; the filter circuit at least comprises a group of capacitors;

the number of the controllable switch modules is the same as the number of phases of the output end of the inverter DCAC circuit;

the output end of the inverter DCAC circuit is connected with the input end of the filter circuit;

the output ends of at least one group of capacitors in the filter circuit are connected with the corresponding controllable switch module;

and the controller is used for controlling the controllable switch module to be switched off when receiving a shutdown instruction.

Preferably, the method further comprises the following steps: an absorption capacitor module;

the number of the absorption capacitor modules is the same as that of the phases at the output end of the inverter DCAC circuit, and the absorption capacitor modules correspond to the inverter DCAC circuit one by one; the absorption capacitor module comprises at least one absorption capacitor;

and two ends of each controllable switch module are connected with the corresponding absorption capacitor module in parallel.

the number of the absorption capacitor modules is the same as that of the controllable switch modules, and when the absorption capacitor modules comprise a plurality of absorption capacitors, the absorption capacitors are connected in parallel to form the absorption capacitor modules;

when the output end of the inverter is three-phase, the number of the absorption capacitor modules is three, and the three absorption capacitor modules are connected between the controllable switch module and the alternating current network side in a star shape or an angular shape.

Preferably, the controller is specifically configured to stop chopping of the inverter DCAC circuit when it is determined that the input end of the inverter is short-circuited according to the input voltage and the input current of the inverter, and control the controllable switching tubes to be all turned off after a first preset time.

Preferably, the controller is further configured to control the controllable switch tube modules to be turned on when the inverter works normally, and control the inverter DCAC circuit to chop after a second preset time.

Preferably, the filter circuit comprises any one of the following forms: an LC circuit, an LCL circuit, or a CLC circuit; wherein L represents inductance and C represents capacitance.

Preferably, when the filter circuit comprises an LC circuit, the LC circuit comprises a filter inductor and a filter capacitor;

the filter inductor is connected between the output end of the inverter DCAC circuit and the controllable switch module in series, and the filter capacitor is connected between the filter inductor and the controllable switch module in a star shape or an angular shape;

further comprising: and the grid-connected switch is connected between the controllable switch module and the output end of the inverter in series.

Preferably, the controllable switch module is integrated with the filter circuit.

Preferably, the number of the inverters is multiple, and the output ends of the inverters are connected in parallel to share the filter circuit and the controllable switch module.

The present application also provides a power supply system including the inverter introduced above, further including: a direct current power supply; and the output end of the direct current power supply is connected with the input end of the inverter.

Preferably, the dc power source is derived from a photovoltaic array, an energy storage battery or wind power generation.

The present application also provides a method for protecting a dc side of an inverter, the inverter including: the inverter DCAC circuit, the filter circuit and the controllable switch module; the number of the controllable switch modules is the same as the number of phases of the output end of the inverter DCAC circuit; each controllable switch module comprises at least one controllable switch tube; the output end of the inverter DCAC circuit is connected with the input end of the filter circuit; the output end of the capacitor in the filter circuit is connected with a corresponding controllable switch module;

the method comprises the following steps:

judging whether a shutdown instruction is received or not;

and when a shutdown instruction is received, controlling the controllable switch module to be turned off.

Preferably, when the shutdown instruction is triggered by a short circuit occurring at the input end of the inverter, determining that the input end of the inverter is short-circuited specifically includes:

judging that the input end of the inverter is short-circuited when the input voltage falling slope of the inverter is greater than a preset value, or the direct current input current amplitude of the inverter is greater than a preset current value, or the alternating current of the inverter is greater than a preset current value;

the controlling the controllable switch module to turn off specifically includes:

and stopping chopping of the inverter DCAC circuit, and controlling the controllable switch module to be switched off after first preset time.

Preferably, the method further comprises the following steps: and when the inverter works normally, the controllable switch module is controlled to be conducted, and the inverter DCAC circuit is controlled to chop after a second preset time.

Therefore, the embodiment of the application has the following beneficial effects:

because the utility model provides an inverter, the controllable switch module of the output series connection of electric capacity in the filter circuit of inverter, when the controller of inverter received the shutdown instruction, the controllable switch module disconnection of control this moment, because the choking characteristic of alternating current inductance, the current rate of rise is restricted during the trouble, turn off the controllable switch module this moment, make the controllable switch module present the high resistance state, thereby utilize the high resistance state of controllable switch module to restrain the impact of short-circuit current, thereby the inside switch tube of protection contravariant DCAC circuit. In addition, when the input end of the inverter is short-circuited, impact current also exists on the alternating current side, and the anti-parallel diode of the controllable switch module can prevent alternating current from flowing back into a switch tube of the inverter. In addition, because the controllable switch module in the inverter provided by the embodiment of the application is connected to the alternating current side of the inverter, when the inverter fails to trigger a shutdown command, for example, when a direct current short circuit exists at the input end of the inverter, the controllable switch module on the alternating current side is controlled to be disconnected, and a switch tube in an inverter DCAC circuit can be protected.

Drawings

Fig. 1 is a schematic diagram of an inverter provided in the prior art;

FIG. 2 is a schematic diagram of another inverter provided by the prior art;

fig. 3 is a schematic diagram of an inverter according to an embodiment of the present disclosure;

fig. 4 is a schematic diagram of another inverter provided in an embodiment of the present application;

fig. 5 is a schematic diagram of another inverter provided in an embodiment of the present application;

fig. 6 is a schematic diagram of a parallel connection of a switching tube and an absorption capacitor according to an embodiment of the present disclosure;

fig. 7 is a timing chart illustrating control of the inverter DCAC circuit and the controllable switching tube during normal operation of the inverter according to the embodiment of the present disclosure;

fig. 8 is a timing diagram illustrating control of the inverter DCAC circuit and the controllable switching tube when the input terminal of the inverter is short-circuited according to the embodiment of the present disclosure;

fig. 9 is a schematic diagram of a power supply system according to an embodiment of the present application;

FIG. 10 is a schematic diagram of another power system provided by an embodiment of the present application;

fig. 11 is a flowchart of a protection method for a dc side of an inverter according to an embodiment of the present application.

Detailed Description

In order to make those skilled in the art better understand the technical solution provided by the present application, a specific application scenario is described below.

The inverter provided by the embodiment of the application is not particularly limited in application scenes, and can be applied to photovoltaic power generation scenes, for example, the input end of the inverter is connected with a photovoltaic array and used for converting direct current of the photovoltaic array into alternating current to realize alternating current grid connection. In addition, the method can also be applied to an energy storage system, namely, the direct current of the energy storage battery is converted into alternating current to be provided as an alternating current load or alternating current grid connection is realized. In addition, the inverter can also be applied to wind power generation scenes.

In inverter equipment, direct current side short circuit is a common fault type, when a direct current bus is short circuited, alternating current power grid energy is poured into a short circuit point, and due to limited tolerance capability, a switch tube rapidly fails under the large current impact of the power grid side, and the switch tube is frequently cracked, and can cause open fire to cause equipment burnout in severe cases.

Inverter embodiment

The present embodiment does not specifically limit the number of phases of the inverter, and may be, for example, a three-phase inverter or a single-phase inverter, and the following description will be given taking an example in which the output terminal of the inverter is three-phase.

Referring to fig. 3, the drawing is a schematic diagram of an inverter provided in an embodiment of the present application.

The present embodiment provides an inverter, including: the inverter DCAC circuit 10, the filter circuit and the controllable switch module; each controllable switch module comprises at least one controllable switch tube; the filter circuit at least comprises a group of capacitors; it should be understood that the group of capacitors herein means that the filter circuit of each phase includes at least one capacitor, but each phase of filter circuit may also include a plurality of capacitors, depending on the specific structure of the filter capacitor, and when each phase includes a plurality of capacitors, the plurality of capacitors are connected in parallel. Similarly, when the controllable switch module includes a plurality of switch tubes, the switch tubes may be connected in parallel. For convenience of description, each controllable switch module includes a switch tube, and a capacitor module includes a capacitor.

The filter circuit comprises any one of the following forms: an LC circuit, an LCL circuit, or a CLC circuit; wherein L represents inductance and C represents capacitance. The embodiment of the present application does not specifically limit the specific topology of the filter circuit, but the controllable switch tube is connected to the output end of the capacitor in the filter circuit, that is, one end of the capacitor connected to one side of the ac power grid.

The output end of the inverter DCAC circuit 10 is connected with the input end of the filter circuit; the output ends of at least one group of capacitors in the filter circuit are connected with corresponding controllable switch tubes;

in this embodiment, the filter circuit includes an inductor and a capacitor, where the number of the inductors is the same as the number of phases at the output end of the inverter DCAC circuit, and each phase of the output end is connected in series with an inductor L.

The filter inductor L is connected in series between the output end of the inverter DCAC circuit 10 and the controllable switch tubes, and the number of the controllable switch tubes is the same as the number of phases at the output end of the inverter DCAC circuit; as shown in fig. 3, the controllable switch transistors include three, which are T7, T8 and T9, and the output end of the inverter DCAC circuit 10 is connected in series with one controllable switch transistor per phase, where the switch transistors connected in series with each phase may be implemented by connecting one or more semiconductor switches in parallel; the filter capacitor Cac1 is connected between the filter inductor L and the controllable switch tube in a star shape or an angular shape;

the input end of the inverter DCAC circuit 10 is connected with a direct current bus capacitor Cdc.

The inverter provided by the embodiment further comprises: and a grid connection switch QS1 connected in series between the controllable switch tube and the output end of the inverter, namely, the controllable switch tube QS1 is connected to the output end of the inverter and is used for being connected with an alternating current power grid during grid connection.

And the controller (not shown in the figure) is used for controlling the controllable switch module to be turned off when the shutdown command is received. For example, the shutdown instruction may be triggered when the input end of the inverter is short-circuited, and in addition, the shutdown instruction may also be triggered by another fault. The controller controls the controllable switching tubes T7-T9 to be turned off; otherwise, the controllable switch tubes are all conducted from T7 to T9. It should be understood that the controllable switch transistors T7-T9 of the three phases need to be synchronized, i.e. the timing of the gate driving signals of the controllable switch transistors is the same.

In addition, the controllable switching tubes T7-T9 all comprise anti-parallel diodes.

The type of the controllable switch tube can be any one of the following types: an Insulated Gate Bipolar Transistor (IGBT), a Metal Oxide Semiconductor field Effect Transistor (MOSFET, hereinafter referred to as MOS Transistor), a SiC MOSFET (Silicon Carbide field Effect Transistor), or the like. When the switching transistor is an MOS transistor, the switching transistor may specifically be a PMOS transistor or an NMOS transistor, which is not specifically limited in this application embodiment. The controllable switching tube can be realized by adopting a semiconductor switching device.

According to the inverter provided by the embodiment of the application, the controllable switch tube is connected in series with the output end of the filter circuit of the inverter, when the direct current input end of the inverter is short-circuited, the controllable switch tube is controlled to be disconnected at the moment, due to the choking characteristic of the alternating current inductor, the current rising rate is limited during short-circuit fault, the controllable switch tube is turned off at the moment, the controllable switch tube is enabled to be in a high-resistance state, and therefore the impact of short-circuit current is restrained by the high-resistance state of the controllable switch tube, and the switch tube in the inverter DCAC circuit 10 is protected. In addition, when the input end of the inverter is short-circuited, impact current also exists on the alternating current side, and the anti-parallel diode of the controllable switch tube can prevent alternating current from flowing back into the switch tube of the inverter. In addition, because the controllable switch tube in the inverter provided by the embodiment of the application is connected to the alternating current side of the inverter, when the direct current short circuit exists at the input end of the inverter, the controllable switch tube on the alternating current side is controlled to be switched off, and the switch tube in the inverter DCAC circuit can be protected.

Another implementation of the inverter provided in the embodiments of the present application is described below with reference to the accompanying drawings.

Referring to fig. 4, the diagram is a schematic diagram of another inverter provided in the embodiment of the present application.

Because the equivalent inductance Lg exists on one side of the alternating-current power grid, and the equivalent inductance Lg can cause the controllable switching tubes T7-T9 to bear larger voltage stress when being turned off, in order to protect the controllable switching tubes T7-T9 and reduce the voltage stress of the controllable switching tubes T7-T9, the inverter provided by the embodiment of the application further includes: an absorption capacitor module; the absorption capacitor module comprises at least one absorption capacitor, and the description is given by taking an example that one absorption capacitor module comprises one absorption capacitor; the following description continues with an example in which the output of the inverter includes three phases.

The number of the absorption capacitor modules is the same as that of the controllable switch modules, and the absorption capacitor modules correspond to the controllable switch modules one by one, wherein each group of the absorption capacitor modules can be connected in parallel by one or more absorption capacitors; as shown in fig. 4, the inverter includes three sets of absorption capacitors, C1, C2, and C3, respectively.

The two ends of each controllable switch tube are connected with corresponding absorption capacitors in parallel, namely, the absorption capacitor C1 is connected with the two ends of the controllable switch tube T7 in parallel, the absorption capacitor C2 is connected with the two ends of the controllable switch tube T8 in parallel, the absorption capacitor C3 is connected with the two ends of the controllable switch tube T9 in parallel, and the absorption capacitors are mainly used for clamping the voltages at the two ends of the controllable switch tube to prevent the controllable switch tube from bearing overlarge voltage stress.

The absorption capacitor provided by the embodiment of the present application may have another connection mode, similar to the connection mode of the filter capacitor, besides the connection mode shown in fig. 4, which is described in detail below with reference to the accompanying drawings.

Referring to fig. 5, the drawing is a schematic view of another inverter provided in the embodiments of the present application.

The inverter that this application embodiment provided still includes: an absorption capacitor module;

the number of the absorption capacitor modules is the same as that of the controllable switch tubes;

when the output end of the inverter is three-phase, the number of the absorption capacitor modules is three, the three absorption capacitor modules are connected between the controllable switch tube and the alternating current network side in a star shape or an angular shape, and each group of the absorption capacitor modules can comprise one absorption capacitor or a plurality of absorption capacitors connected together in parallel.

As shown in fig. 5, three absorption capacitors Cac2 are connected in a delta shape to the output end of the controllable switch tube, i.e. the ac grid side of the controllable switch tube, and when the inverter includes a grid-connected switch QS1, three absorption capacitors Cac2 are connected in a delta shape between the output end of the controllable switch tube and the grid-connected switch QS 1. The absorption capacitor mainly absorbs the impact current of the controllable switch tube, and the controllable switch tube is prevented from bearing excessive voltage stress.

The Cac2 also acts as a filter capacitor for the absorption capacitor shown in fig. 5.

Besides the connection of the two absorption capacitors shown in fig. 4 and 5, the connection of the absorption capacitor and the controllable switch tube can also be as shown in fig. 6.

Referring to fig. 6, another connection manner of the absorption capacitor and the controllable switch tube is provided in this embodiment of the present application.

The controllable switch module provided by this embodiment includes a plurality of controllable switch transistors connected in parallel, and the absorption capacitor module includes a plurality of absorption capacitors connected in parallel, that is, the plurality of absorption capacitors can suppress the peak voltage of the plurality of controllable switch transistors.

The control timing of the inverter for the controllable switching tube provided by the embodiment of the present application is specifically described below with reference to the accompanying drawings.

Referring to fig. 7, the control timing diagram of the inverter DCAC circuit and the controllable switching tube during normal operation of the inverter according to the embodiment of the present application is shown.

The inverter provided by the embodiment further comprises a controller, wherein the controller is used for controlling the controllable switch tubes to be conducted when the inverter works normally, and controlling the inverter DCAC circuit to chop after second preset time.

As can be seen from fig. 7, the high level rising edge of the driving signal of the controllable switching tube T7-T9 leads the driving signal of the switching tube of the inverter DCAC circuit in the inverter by a second preset time period T2.

In addition, in order to ensure the safety of the switching tube in the inverter DCAC circuit, the controller controls the driving signal of the controllable switching tube T7-T9 to be changed to the low level after the switching tube in the inverter DCAC circuit stops driving, i.e. the chopping is stopped for the third preset time T3.

In the embodiment of the present application, when the driving signal of the controllable switch transistor T7-T9 is at a high level, the controllable switch transistor is turned on, and when the driving signal is at a low level, the controllable switch transistor is turned off.

The driving sequence of the controllable switch tube and the switch tube in the inverter DCAC circuit when the inverter normally works is described above, and the driving sequence of the controllable switch tube and the switch tube in the inverter DCAC circuit when the dc input end of the inverter is short-circuited is described below.

Referring to fig. 8, the control timing diagram of the inverter DCAC circuit and the controllable switch tube when the input end of the inverter is short-circuited is shown.

And the controller is used for stopping chopping of the inverter DCAC circuit when judging that the input end of the inverter is short-circuited according to the input voltage and the input current of the inverter, and controlling the controllable switching tubes to be turned off after a first preset time t 1.

As can be seen from the figure, the driving signal of the switching tube in the inverter DCAC circuit is stopped first, i.e. chopping is stopped, and the low-level falling edge of the driving signal of the controllable switching tube T7-T9 lags behind the driving signal T1 time period of the switching tube in the inverter DCAC circuit. Namely, the wave-sealing is firstly carried out on the switching tube in the inverter DCAC circuit, and then the controllable switching tube T7-T9 is controlled to be disconnected. Because some switching tubes may still be in operation when the dc input of the inverter is short-circuited, the time lag T1 is to wait for all the switching tubes in the inverter DCAC circuit to stop operating before controlling the controllable switching tubes T7-T9 to turn off.

In addition, in the embodiment of the present application, the controller determines that the input terminal of the inverter is short-circuited, specifically, the controller may detect an input voltage and a dc input current of the inverter, and determine that the input terminal of the inverter is short-circuited when a falling slope of the input voltage of the inverter is greater than a preset value, or a dc input current amplitude of the inverter is greater than a preset current value, or an ac current is greater than a preset value.

In the embodiment of the present application, the specific values of the preset voltage reduction slope value and the preset current value are not specifically limited, and may be set according to a specific application scenario of the inverter.

For example, in one possible implementation, it is determined whether the input voltage of the inverter is suddenly decreased, i.e., suddenly dropped, and if the input voltage is 1000V when the inverter normally operates, if the input voltage drops with a slope of-500V/ms, it is determined that the input terminal of the inverter is short-circuited.

The above embodiments describe the inverter, wherein the controllable switch module may be integrated with the filter circuit, i.e. the controllable switch module is integrated inside the filter circuit. When the power station comprises a plurality of inverters, the inverters can share the same set of filter circuit and the controllable switch module, for example, the output ends of the inverters are connected in parallel and then connected with the filter circuit and the controllable switch module, so that the integration level can be improved, and the hardware cost is saved.

In addition, the inverter provided by the embodiment of the application can be suitable for a micro-grid on-grid and off-grid seamless switching scene, and when alternating current grid connection is carried out, the controller modulates the amplitude and the phase of the output voltage of the inverter by controlling the driving signal of the switching tube in the inverter DCAC circuit. And when the frequency of the inverter is the same as the frequency of the power grid and the amplitude of the inverter is the same as the frequency of the power grid, closing a grid-connected switch, and carrying out grid-connected operation on the inverter. When the alternating current power grid disappears, the controller controls the grid-connected switch to be switched off to operate in an off-grid mode, the local load is not affected, the amplitude and the phase of the output voltage of the inverter are repeatedly adjusted when the alternating current power grid recovers, and the grid-connected switch is closed to operate in the grid-connected mode when a switch-on condition is achieved.

Power supply system embodiment

Based on the inverter provided by the above embodiments, the embodiments of the present application further provide a power supply system, which is described in detail below with reference to the accompanying drawings.

Referring to fig. 9, the figure is a schematic diagram of a power supply system according to an embodiment of the present application.

The power supply system provided by the embodiment of the application comprises: the inverter 100 described in any of the above embodiments further includes: a direct current power supply; the source of the direct current power source is not particularly limited, and the direct current power source can be derived from a photovoltaic array, an energy storage battery or wind power generation.

The input terminal of the inverter 100 may be directly connected to the dc power supply, or may be connected to the dc power supply via another converter. And the direct current power supply can be a direct source and can also be a device for converting alternating current into direct current.

The following description is given by taking an application in a photovoltaic system as an example, and for example, the power supply system further includes: a direct current-direct current (DCDC) circuit 200;

the output of the DCDC circuit 200 is connected to the input of the inverter 100.

The output end of the inverter provided by the embodiment of the application is connected with the controllable switch tube, and even if a short circuit occurs between the DCDC circuit 200 and the inverter 100, the power supply system provided by the embodiment of the application can protect the switch tube in the inverter. It should be understood that the dc input of the inverter may be shorted, either at the input of the DCDC circuit 200, at the output of the DCDC circuit 200, or at the DCDC circuit 200 itself.

The embodiment of the present application does not specifically limit the source of the dc power at the input end of the DCDC circuit 200, and for example, the dc power may be a photovoltaic panel, which is described in the following with a photovoltaic power generation scenario.

The power supply system provided by this embodiment further includes: photovoltaic array 300, the input of DCDC circuit 200 connects photovoltaic array 300.

In addition, the power supply system provided in the embodiment of the present application may further include: an energy storage battery and a bidirectional DCDC circuit;

referring to fig. 10, a schematic diagram of another power supply system provided in the embodiment of the present application is shown.

That is, the energy storage battery 400 is connected to the input terminal of the inverter 100 through the bidirectional DCDC circuit 500.

It should be understood that, in order to increase the capacity of the whole power supply system, a plurality of inverters can be included, the output ends of the plurality of inverters are connected in parallel, namely parallel connection for grid-connected power supply is realized, and the plurality of inverters share a set of filter circuit and controllable switch module.

Method embodiment

Based on the inverter and the power supply system provided by the above embodiments, the embodiments of the present application further provide a protection method for the dc side of the inverter, which is described in detail below with reference to the accompanying drawings.

Referring to fig. 11, the figure is a flowchart of a protection method for a dc side of an inverter according to an embodiment of the present application.

In the method for protecting the dc side of the inverter provided in this embodiment, the inverter includes: the system comprises an inverter DCAC circuit, a filter circuit and a controllable switch module; each controllable switch module comprises at least one controllable switch tube; the number of the controllable switch modules is the same as the number of phases of the output end of the inverter DCAC circuit; the output end of the inverter DCAC circuit is connected with the input end of the filter circuit; the output end of the capacitor in the filter circuit is connected with a corresponding controllable switch module;

s1001: judging whether a shutdown instruction is received or not; if yes, S1002 is executed.

The method and the device for triggering the shutdown command are not limited, and the shutdown command can be triggered by various faults, for example, a direct current input end of an inverter is short-circuited.

S1002: when a shutdown instruction is received, the controllable switch modules are controlled to be turned off.

Because the output end of the capacitor is connected with the controllable switch module in series in the filter circuit of the inverter, when the direct current input end of the inverter is short-circuited, the controllable switch module is controlled to be disconnected, the current rising rate is limited when the short-circuit fault occurs due to the choking characteristic of the alternating current inductor, the controllable switch module is turned off at the moment, the controllable switch tube is in a high-resistance state, and therefore the impact of the short-circuit current is restrained by the high-resistance state of the controllable switch module, and the switch tube in the inverter DCAC circuit is protected. In addition, when the input end of the inverter is short-circuited, impact current also exists on the alternating current side, and the anti-parallel diode of the controllable switch module can prevent alternating current from flowing back into a switch tube of the inverter. In addition, because the controllable switch module in the inverter provided by the embodiment of the application is connected to the alternating current side of the inverter, when the direct current short circuit exists at the input end of the inverter, the controllable switch module on the alternating current side is controlled to be switched off, and a switch tube in an inverter DCAC circuit can be protected.

Judging whether the input end of the inverter is short-circuited or not, specifically comprising:

judging that the input end of the inverter is short-circuited when the input voltage of the inverter is smaller than a preset voltage value and the input current of the inverter is larger than a preset current value;

controlling the controllable switch modules to be turned off, specifically comprising:

and stopping chopping of the inverter DCAC circuit, and controlling the controllable switch module to be switched off after the first preset time.

It should be understood that in principle the controllable switch modules in the three phases should be turned off simultaneously, but in practice there may be dead time delays due to errors, or protection.

In order to protect the switching tube in the inverter DCAC circuit, the protection method provided by this embodiment further includes: and when the inverter works normally, the controllable switch module is controlled to be conducted, and the inverter DCAC circuit is controlled to chop after a second preset time.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An inverter, comprising: the device comprises a controller, an inverter DCAC circuit, a filter circuit and a controllable switch module; each controllable switch module comprises at least one controllable switch tube; the filter circuit at least comprises a group of capacitors;

and the controller is used for controlling the controllable switch module to be switched off when the shutdown instruction is received.

2. The inverter of claim 1, further comprising: an absorption capacitor module;

and the two ends of each controllable switch module are connected with the corresponding absorption capacitor module in parallel.

3. The inverter of claim 1, further comprising: an absorption capacitor module;

4. The inverter according to any one of claims 1 to 3, wherein the controller is specifically configured to stop chopping of the inverting DCAC circuit when it is determined that the input end of the inverter is short-circuited according to the input voltage and the input current of the inverter, and control the controllable switching tubes to be turned off after a first preset time.

5. The inverter according to any one of claims 1 to 3, wherein the controller is further configured to control the controllable switch tube modules to be turned on when the inverter is in normal operation, and to control the inverter DCAC circuit to chop after a second preset time.

6. An inverter according to any of claims 1-3, wherein the filter circuit comprises any of the following forms: an LC circuit, an LCL circuit, or a CLC circuit; wherein L represents inductance and C represents capacitance.

7. The inverter of claim 6, wherein when the filter circuit comprises an LC circuit, the LC circuit comprises a filter inductance and a filter capacitance;

8. An inverter according to any one of claims 1-3, wherein the controllable switch modules are integrated with the filter circuit.

9. The inverter of claim 8, wherein the inverter is a plurality of inverters, and the output terminals of the plurality of inverters are connected in parallel to share the filter circuit and the controllable switch module.

10. A power supply system, comprising: the inverter of any one of claims 1-9, further comprising: a direct current power supply;

and the output end of the direct current power supply is connected with the input end of the inverter.

11. The power system of claim 10, wherein the dc power source is derived from a photovoltaic array, an energy storage battery, or wind power.

12. A method for protecting a dc side of an inverter, the inverter comprising: the inverter DCAC circuit, the filter circuit and the controllable switch module; the number of the controllable switch modules is the same as the number of phases of the output end of the inverter DCAC circuit; each controllable switch module comprises at least one controllable switch tube; the output end of the inverter DCAC circuit is connected with the input end of the filter circuit; the output end of the capacitor in the filter circuit is connected with a corresponding controllable switch module;

the method comprises the following steps:

judging whether a shutdown instruction is received or not;

13. The protection method according to claim 12, wherein when the shutdown command is triggered by a short circuit occurring at the input terminal of the inverter, determining that the input terminal of the inverter is short-circuited specifically includes:

the controlling the controllable switch module to be turned off specifically comprises:

14. The protection method according to claim 12 or 13, further comprising: and when the inverter works normally, the controllable switch module is controlled to be conducted, and the inverter DCAC circuit is controlled to chop after a second preset time.