Inverter and inverter turn-off method

Abstract

The invention provides an inverter and an inverter turn-off method, and relates to the technical field of inverters.The inverter turn-off method comprises the steps that in response to a ground short circuit fault, wave sealing processing is conducted on an inverter circuit; after the inverter circuit completes wave sealing, in response to the situation that the first current parameter of the switch module is smaller than or equal to the safe current value of the switch module at the current moment, the change trend of the first current parameter of the switch module corresponding to the current moment is determined, and the safe current value is larger than zero; and when the change trend of the first current parameter is a descending trend, controlling the switch module to be turned off. Therefore, the relay can be prevented from being impacted by large current, stable turn-off of a short-circuit loop is realized, the safety of system operation is improved, and the service life of the relay is prolonged.

Description

[0001] This invention claims priority to the Chinese patent application filed with the Patent Office of China on February 8, 2024, with application number 202410178260.1 and invention name “AN INVERTER, A METHOD FOR SHUTDOWNING THE INVERTER AND A PHOTOVOLTAIC SYSTEM”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the technical field of inverters, and in particular to an inverter and a method for shutting down an inverter. Background Art

[0003] In a photovoltaic system, when a short circuit to ground occurs in the DC source connected to the input of the photovoltaic inverter, it will cause damage to the inverter. Therefore, the short circuit to ground needs to be shut off in time.

[0004] At present, the short-circuit current still exists after the inverter is blocked, and it is necessary to control the corresponding relay to shut down to cut off the short-circuit current. However, when the relay is shut down at a high current, the service life of the relay will be seriously affected. Summary of the Invention

[0005] In view of this, the present application provides an inverter and an inverter shutdown method, which aims to safely shut down the relay when the DC side cable of the inverter is short-circuited to the ground.

[0006] In a first aspect, an inverter includes: an inverter circuit, a switch module, and a controller, wherein an input end of the inverter circuit is connected to a DC source, an output end of the inverter circuit is connected to the switch module, and an output end of the switch module is connected to a power grid; the controller is configured to:

[0007] In response to a short-circuit fault to ground, performing a wave blocking process on the inverter circuit;

[0008] After the inverter circuit completes wave sealing, in response to the first current parameter of the switch module at a current moment being less than or equal to the safety current value of the switch module, determining a change trend of the first current parameter of the switch module corresponding to the current moment, the safety current value being greater than zero;

[0009] When the change trend of the first current parameter is a downward trend, the switch module is controlled to be turned off.

[0010] Optionally, when the change trend of the first current parameter is a downward trend, controlling the switch module to turn off includes:

[0011] In response to the change trend of the first current parameter being a downward trend, controlling the switch module to be turned off; or,

[0012] In response to the first current parameter changing in a downward trend, the switch module is controlled to be turned off at any moment within a preset time period starting from when the first current parameter is less than or equal to the safe current value of the switch module.

[0013] Optionally, the inverter circuit includes an upper half bridge arm and a lower half bridge arm;

[0014] The performing wave sealing processing on the inverter circuit includes:

[0015] Turn off the driving of each switch tube in the upper half bridge arm and the lower half bridge arm; or,

[0016] When the short-circuit fault to ground is caused by a short circuit between the negative electrode of the DC source and the ground, and the withstand current of each switch in the lower half bridge arm is greater than the maximum short-circuit current of the short circuit between the negative electrode of the DC source and the ground, turning off the driving of each switch in the upper half bridge arm;

[0017] When the short-circuit fault to ground is caused by a short circuit between the positive electrode of the DC source and the ground, and the withstand current of each switch tube in the upper half bridge arm is greater than the maximum short-circuit current of the short circuit between the positive electrode of the DC source and the ground, the driving of each switch tube in the lower half bridge arm is turned off.

[0018] Optionally, the safe current value is a current value corresponding to a first time point, where the first time point is a periodic time point determined by subtracting a delay time from a time point when the first current parameter drops to zero in a current parameter periodic curve corresponding to the switch module, where the delay time is the time from when a shutdown signal is sent to the switch module to when the switch module is actually shut down;

[0019] The preset duration is a first duration during which the first current parameter value of the switch module is zero.

[0020] Optionally, the safety current value is the maximum impact current value of the switch module, or the safety current value is the current value corresponding to a second time point, the second time point is a periodic time point determined by subtracting a delay time and a withstand time from a time point when the first current parameter drops to zero in a current parameter periodic curve corresponding to the switch module, the delay time is the time from the moment when a shutdown signal is sent to the switch module to the moment when the switch module is actually shut down, the withstand time is the time from the moment when the first current parameter shows a downward trend to the moment when the maximum impact current value of the switch module corresponds to the time point when the first current parameter drops to zero, and the maximum impact current value is greater than zero;

[0021] The preset time length is the sum of the first time length when the current value of the switch module is zero and twice the power-withstanding time length.

[0022] Optionally, the safety current value is zero; after the inverter circuit completes wave sealing, the controller is also used to, in response to the first current parameter changing trend being a downward trend, control the switch module to shut down within a preset time length of the first time length when the first current parameter of the switch module is zero, starting from the time when the first current parameter of the switch module is collected to be zero.

[0023] Optionally, the calculation formula for the first duration is:

[0024]

[0025] Wherein, ΔT is the first time length between the moment when the current parameter of the switch module is zero and the moment when the voltage value of the most recent switch module is zero when the current parameter of the switch module is in a downward trend. U is the rated voltage value of the phase power corresponding to the switch module, V is the voltage value of the phase power corresponding to the switch module, and f is the frequency of the phase power corresponding to the switch module.

[0026] Optionally, the safety current value is greater than 0, and after responding that the first current parameter of the switch module at the current moment is less than or equal to the safety current value of the switch module, the method further includes:

[0027] Determining whether the first current parameter is less than or equal to a preset safety value; wherein the preset safety value is less than the safe current value;

[0028] When the first current value parameter is less than or equal to the preset safety value, the switch module is controlled to be turned off.

[0029] Optionally, the inverter circuit outputs three-phase electricity, and the controller is further configured to:

[0030] Before controlling the switch module corresponding to the first current parameter to turn off, determine that among the three switch modules corresponding to the three phases of electricity, except the switch module corresponding to the phase of electricity corresponding to the first current parameter, the switch modules corresponding to the first current parameter in the other two switch modules are completed to turn off, and the switch modules whose current parameters are less than or equal to the threshold value; while controlling the switch module corresponding to the first current parameter to turn off, the switch modules whose current parameters are less than or equal to the threshold value are controlled to turn off.

[0031] Optionally, the switch module whose current parameter is less than or equal to the threshold is a switch module whose current parameter is zero at the moment when the first current parameter drops to zero;

[0032] When controlling the switch module corresponding to the first current parameter to be turned off and simultaneously controlling the switch module having a current value less than or equal to the threshold to be turned off, the controller is configured to:

[0033] Within a set time period starting from when the first current parameter is less than or equal to the safe current value of the switch module, the switch module corresponding to the first current parameter is controlled to be turned off while the switch module with the second current value of zero is controlled to be turned off.

[0034] Optionally, the calculation formula for the set duration is:

[0035]

[0036] Wherein, ΔT is the first time length between the time point when the first current parameter is zero and the time point when the most recent voltage value is zero when the first current parameter is in a downward trend. f is the frequency of the phase power transmitted by the switching module corresponding to the first current parameter.

[0037] Optionally, determining a change trend of the first current parameter of the switch module corresponding to the current moment includes:

[0038] For the switch module, continuously collect multiple first current parameters starting from the current moment, and determine the change trends of the multiple first current parameters according to the collection time as the first current parameter change trend of the switch module corresponding to the current moment; or,

[0039] Determine a change trend of the first current parameter of the switch module corresponding to the current moment based on the first current parameter of the switch module recorded before the current moment; or

[0040] After waiting for a specified time period starting from the current moment, the first current parameter of the switch module is reacquired, and a current parameter change trend of the switch module is determined based on a magnitude relationship between the two first current parameters before and after the waiting for the specified time period.

[0041] Optionally, the controller is further configured to respond to a relay shutdown instruction and control the switch module to be turned off at a zero current moment when the inverter circuit is blocked.

[0042] Optionally, the topology of the inverter circuit is one of NPC, TNPC, HERIC and ANPC.

[0043] Optionally, the switch module includes at least two relay switches, and a control end of each relay switch is connected to the controller;

[0044] The controlling the switch module to turn off includes:

[0045] Control a relay switch in the switch module to turn off.

[0046] Optionally, the DC source is a photovoltaic string.

[0047] In a second aspect, the present application further provides a method for shutting down an inverter, wherein the inverter includes: an inverter circuit, a switch module, and a controller, wherein the input end of the inverter circuit is connected to a DC source, the output end of the inverter circuit is connected to the switch module, and the output end of the switch module is used to connect to a power grid; the method includes:

[0048] In response to a short-circuit fault to ground, performing a wave blocking process on the inverter circuit;

[0049] After the inverter circuit completes wave sealing, in response to the first current parameter of the switch module at a current moment being less than or equal to the safety current value of the switch module, determining a change trend of the first current parameter of the switch module corresponding to the current moment, the safety current value being greater than zero;

[0050] When the change trend of the first current parameter is a downward trend, the switch module is controlled to be turned off.

[0051] In a third aspect, the present application further provides a photovoltaic system, comprising a photovoltaic string and an inverter, wherein the photovoltaic string is connected to an input terminal of the inverter to provide direct current to the inverter;

[0052] The output end of the inverter is connected to the power grid, and is used to convert direct current into alternating current and transmit it to the power grid. The inverter is any one of the inverters described above, and / or an inverter applying the above method.

[0053] The present application provides an inverter and an inverter shutdown method. In the present application, the inverter performs a wave sealing process on the inverter circuit in response to a short circuit to ground fault; after the inverter circuit completes the wave sealing process, in response to the first current parameter of the switch module being less than or equal to the safe current value of the switch module at the current moment, the first current parameter change trend of the switch module corresponding to the current moment is determined, and the safe current value is greater than zero; when the change trend of the first current parameter is a downward trend, the switch module is controlled to be shut down. In this way, after completing the wave sealing process of the inverter circuit, when it is determined that the first current parameter of the switch module is not higher than the safe current value for achieving safe shutdown, combined with the current change trend of the switch module, the switch module is controlled to be shut down when it is in a downward trend, thereby avoiding the relay from being impacted by a large current, achieving stable shutdown of the short-circuit loop, and improving the safety of system operation and the service life of the relay. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in this embodiment or the prior art, the following briefly introduces the drawings required for use in the embodiment or the prior art description. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0055] Figure 1 A schematic diagram of an inverter circuit provided in an embodiment of the present application;

[0056] Figure 2 A schematic structural diagram of another inverter provided in an embodiment of the present application;

[0057] Figure 3 A schematic diagram of a current cycle curve and a voltage cycle curve of a switching module when the negative electrode of a DC source is short-circuited to ground, provided in an embodiment of the present application;

[0058] Figure 4 A schematic diagram of a flow chart of an inverter shutdown method provided in an embodiment of the present application;

[0059] Figure 5 A schematic diagram of a loop formed by two un-disconnected phase switch modules and a power grid in an inverter circuit provided by an embodiment of the present application;

[0060] Figure 6 A circuit diagram of a plurality of DC sources connected in parallel to a power grid through corresponding inverter circuits provided in an embodiment of the present application. DETAILED DESCRIPTION

[0061] Inverter short circuit will cause damage to the inverter. For example, in a photovoltaic inverter, the photovoltaic string connected to the input end of the photovoltaic inverter has a short circuit loop between the positive or negative pole of the photovoltaic string and the ground (such as Figure 1 In the inverter circuit diagram shown in FIG, the negative pole of the photovoltaic string is short-circuited to the ground as indicated by the arrow flow direction, which will damage the inverter. Therefore, the photovoltaic string short-circuit to the ground loop needs to be shut off in time. At present, the short-circuit current still exists after the inverter is blocked, and the output of multiple phases of the inverter needs to be disconnected. Figure 1 As shown in the figure, the D group main relay simultaneously controls the disconnection of K1, K3, and K5, and then the F group main relay simultaneously controls the disconnection of K2, K4, and K6, thereby controlling the output of multiple phases of the inverter. However, when disconnecting multiple phases of the inverter output at the same time, due to the different phases of the three phases, it is easy for a large current to flow through the relay when turning off a phase relay, which can easily damage the relay.

[0062] Based on the above problems, the present application provides an inverter, comprising: an inverter circuit, a switch module, and a controller, wherein the input end of the inverter circuit is connected to a DC source, the output end of the inverter circuit is connected to the switch module, and the output end of the switch module is used to connect to the power grid; the controller is used to: in response to a ground short circuit fault, perform a wave capping process on the inverter circuit; after the inverter circuit completes the wave capping process, in response to the first current parameter of the switch module at the current moment being less than or equal to the safe current value of the switch module, determine the change trend of the first current parameter of the switch module corresponding to the current moment, and the safe current value is greater than zero; when the change trend of the first current parameter is a downward trend, control the switch module to shut down. In this way, after completing the wave capping process of the inverter circuit, when it is determined that the first current parameter of the switch module is not higher than the safe current value for achieving safe shutdown, the switch module is controlled to shut down when the first current parameter is on a downward trend, in combination with the current change trend of the switch module, to avoid the relay from being subjected to a large current shock, achieve stable shutdown of the short circuit loop, and improve the safety of system operation and the service life of the relay.

[0063] The present application can not only control the switch module to shut down in response to the first current parameter changing in a downward trend, but also control the switch module to shut down at any time within a preset time period starting from when the first current parameter is less than or equal to the safe current value of the switch module in response to the first current parameter changing in a downward trend. In this way, by setting the preset time period, the controller can expand the time range for controlling the relay to shut down, giving the relay body a longer shutdown time range, better adapting to the time consumed by the shutdown process, reducing the need to wait for the next cycle to shut down, and thus reducing the switch from being subjected to another large current shock while waiting for the next cycle.

[0064] Furthermore, the present application aims at a three-phase inverter circuit, reducing the problem of turning off only one phase of the short-circuit loop, causing the switch modules of the remaining two phases to form a loop with the power grid and the load, resulting in abnormal current in the remaining two phases, for example, see Figure 5 The schematic diagram of the circuit formed by the switch modules of the two phases of the inverter circuit that are not turned off and the power grid can be seen in Figure 5 The middle dotted line indicates that after the phase A relay is cut off, capacitor C1 is cut off, while C2 and C3 are not cut off and form a loop with the grid and load, resulting in abnormal current in the remaining two phases. Alternatively, see Figure 6 The circuit diagram shown is a circuit diagram of a plurality of DC sources connected in parallel to a power grid through corresponding inverter circuits, wherein the plurality of DC sources (eg Figure 6In the case where the machine 1 and machine 2 are connected to the grid in parallel through the corresponding inverter circuit, the phase A relay of machine 2 is disconnected, capacitor C4 is cut off, and the current of machine 1 forms a loop through C5 and C6 with the two phases of the faulty machine that are not disconnected (see Figure 6 The dotted line in the figure shows the current i B 、i C In summary, the three-phase imbalance of the grid line voltage will lead to phase current disorder and make it impossible to accurately identify the zero-current shutdown timing of the other two-phase relays. Therefore, for the three-phase power inverter circuit, this application adopts the method of simultaneously cutting off the two-phase relays to avoid a loop, which can effectively avoid the problem of three-phase imbalance of the grid line voltage.

[0065] In addition, each switch module can include multiple relay switches connected in series, and the control terminal of each relay switch can be connected to a controller separately. Providing multiple redundant switches on the switch module allows for alternate use of the switches, extending the life of each switch.

[0066] In order to be able to understand the features and technical content of the embodiments of the present disclosure in more detail, the implementation of the embodiments of the present disclosure is described in detail below in conjunction with the accompanying drawings. The accompanying drawings are for reference only and are not used to limit the embodiments of the present disclosure. In the following technical description, for the sake of convenience of explanation, a full understanding of the disclosed embodiments is provided through multiple details. However, one or more embodiments can still be implemented without these details. In other cases, to simplify the drawings, well-known structures and devices can be simplified for display.

[0067] In the description and claims of the embodiments of the present disclosure, as well as in the accompanying drawings, the terms "first," "second," and the like are used to distinguish similar items and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate to describe the embodiments of the present disclosure herein. In addition, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions.

[0068] Unless otherwise stated, the term "plurality" means two or more.

[0069] In the embodiment of the present disclosure, the character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B means: A or B.

[0070] The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0071] In order to make the purpose, technical solutions and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0072] See also Figure 2 A structural schematic diagram of another inverter is shown, an inverter comprising: an inverter circuit, a switch module and a controller, the input end of the inverter circuit being connected to a DC source, the output end of the inverter circuit being connected to the switch module, and the output end of the switch module being used to connect to a power grid; the controller being used to: in response to a short circuit to ground fault, perform wave sealing processing on the inverter circuit; after the inverter circuit completes wave sealing, in response to the first current parameter of the switch module being less than or equal to the safety current value of the switch module at the current moment, determine the change trend of the first current parameter of the switch module corresponding to the current moment, the safety current value being greater than zero; when the change trend of the first current parameter is a downward trend, control the switch module to shut down.

[0073] The DC source mentioned above may be a photovoltaic string, or a DC bus connected to multiple photovoltaic strings, or of course, may be other energy storage modules capable of storing DC power.

[0074] The switch module may include at least one relay switch. By controlling one or more relay switches in the switch module to be turned off by the controller, the switch module can be turned off.

[0075] The above inverter circuit can be a single-phase inverter circuit or a multi-phase inverter circuit. Figure 2 The inverter circuit shown is a three-phase inverter circuit. Figure 2 The three-phase inverter circuit is provided with switch modules in Group A, Group B, and Group C. Each switch module group is connected in series with at least two switches. For example, the switch module in Group A is connected in series with K1 and K2. Each phase of the inverter circuit is connected to the power grid through the switch module. For example, after the switch module in Group A is connected in series with K1 and K2, it is output to the power grid through output port A of the switch module in Group A. Similarly, output port B of the switch module in Group B and output port C of the switch module in Group C also transmit the corresponding phase power to the power grid.

[0076] When the positive pole of the DC source is short-circuited to the ground, the current in the short-circuit loop is collected and located on the negative half-axis. The above-mentioned first current parameter can be the absolute value of the current of the switch module, so that when it is subsequently determined that the current value is lower than the safe current value, the absolute value of the current is lower than the safe current value, and the relay can be turned off under a smaller current impact; when the negative pole of the DC source is short-circuited to the ground, the current in the short-circuit loop is collected and located on the positive half-axis. The above-mentioned first current parameter can be the current value of the corresponding switch module.

[0077] Based on the above-mentioned inverter, after completing the wave sealing processing of the inverter circuit, when it is determined that the first current parameter of the switch module is not higher than the safe current value for achieving safe shutdown, combined with the current change trend of the switch module, when it is in a downward trend, that is, lower than the safe current value, the switch module is controlled to be shut down, to avoid the relay from being subjected to large current shocks, to achieve stable shutdown of the short-circuit loop, and to improve the safety of system operation and the service life of the relay.

[0078] In the embodiment of the present application, the above Figure 2 There are multiple possible implementations for controlling the switch module to turn off when the change trend of the first current parameter is a downward trend, which are introduced below. It should be noted that the implementations given in the following introduction are only for illustrative purposes and do not represent all implementations of the embodiments of this application.

[0079] In a first possible implementation manner, in response to the first current parameter having a downward trend as a change trend, the switch module is controlled to be turned off.

[0080] In a second possible implementation, in response to the first current parameter changing in a downward trend, the switch module is controlled to be turned off at any moment within a preset time period from when the first current parameter is less than or equal to the safe current value of the switch module.

[0081] Exemplarily, the first possible implementation method mentioned above can be that when the controller determines that the first current parameter is less than or equal to the safe current value of the switch module, the change trend of the first current parameter is a downward trend (for example, the change trend of the first current parameter corresponding to the switch module collected twice or a preset number of times before or after the current moment is a downward trend), the switch module can be controlled to shut down. In this way, the switch module can be shut down at a lower current value to avoid the impact damage to the relay switch in the switch module caused by the large current. In addition, if the monitored current value of the switch module is less than or equal to the safe current value and the current change trend of the switch module is a downward trend, the switch module can be controlled to shut down, and the switch module can be shut down as early as possible, giving the relay body a longer time range for shutdown, which can better adapt to the time consumed by the shutdown process.

[0082] Furthermore, a second possible implementation method can be to control the switch module to shut down within a preset time period starting from the time the first current parameter is determined to be decreasing and the first current parameter is less than or equal to the safe current value of the switch module. This can extend the time range for the controller to perform shutdown control by setting the preset time period, reducing the need to wait for the next cycle before shutting down, thereby reducing the risk of the switch being subjected to another high current shock while waiting for the next cycle.

[0083] Based on the above embodiment, the inverter circuit includes an upper half bridge arm and a lower half bridge arm. When the inverter circuit is subjected to the wave sealing process, the drive of each switch tube in the upper half bridge arm and the lower half bridge arm can be directly turned off. Of course, after the photovoltaic cable is grounded in the photovoltaic system, a corresponding control method can also be adopted according to the two different situations of the DC source positive pole short-circuited to the ground and the negative pole short-circuited to the ground and the tolerance of the switch tube in the inverter circuit. Specifically, when the short-circuit to ground fault is the DC source positive pole short-circuited to the ground, and the tolerance current of each switch tube in the upper half bridge arm is greater than the maximum short-circuit current of the DC source positive pole short-circuited to the ground, the drive of each switch tube in the lower half bridge arm is controlled to be turned off. When the short-circuit to ground fault is the DC source negative pole short-circuited to the ground, and the tolerance current of each switch tube in the lower half bridge arm is greater than the maximum short-circuit current of the DC source negative pole short-circuited to the ground, the drive of each switch tube in the upper half bridge arm is turned off.

[0084] Exemplarily, the above-mentioned switching tube can adopt the semiconductor device MOSFET. If the photovoltaic negative cable has a ground fault, the lower bridge arm includes the semiconductor device MOSFET, then the lower half bridge arm can be turned on, so that the loop current flows through the channel of the lower half bridge arm MOSFET. The MOSFET channel has a smaller impedance than its body diode and can withstand a larger current, thereby reducing device losses and avoiding device failure. Similarly, if the photovoltaic positive cable has a ground fault, the upper bridge arm includes the semiconductor device MOSFET, then the upper half bridge arm can be turned on.

[0085] Based on the above embodiment, according to the power resistance of the relay in the switch module, and the delay time between the controller sending the shutdown signal and the actual shutdown of the relay (the main reasons for the delay time include the signal delay time of the microcontroller unit MCU of the controller, the time required for the relay to shut down, and the shutdown time of the drive circuit, etc., the signal delay time of the microcontroller unit MCU can be given according to human experience, the time required for the relay to shut down can be given according to the relay parameters, and the shutdown time of the drive circuit is determined based on the driving voltage), there are also many possible implementation situations for the value of the safe current value, as follows:

[0086] In one possible implementation, the safety current value is the current value corresponding to the first time point, which is a periodic time point determined by subtracting the delay time from the time when the first current parameter drops to zero in the current parameter periodic curve corresponding to the switch module. The delay time is the time from the moment when the shutdown signal is sent to the switch module to the moment when the switch module is actually shut down.

[0087] For example, see Figure 3 This is a schematic diagram of the current cycle curve and voltage cycle curve of the switch module when the negative electrode of the DC source is short-circuited to the ground according to the embodiment of the present application. Figure 3 Taking the current cycle curve of the A-phase current Ia corresponding to the switching module of the inverter circuit group A as an example, in the descending curve of the current cycle curve, if the time point corresponding to the safe current value is zero is T1, the current value corresponding to the time point obtained by subtracting the delay time of the switching module of group A (the time from the moment the controller sends a shutdown signal to the switching module to the moment the switching module is actually shut down) from the time point T1 is the safe current value of the switching module of group A.

[0088] The preset duration is a first duration during which the first current parameter value of the switch module is zero.

[0089] Therefore, from any moment within the preset time period from when the first current parameter is less than or equal to the safe current value of the switch module, the switch module is controlled to be turned off. Specifically, within the preset time period (the first time period during which the first current parameter value of the switch module is zero) from when the monitoring and collection shows that the first current parameter of the switch module is less than or equal to the safe current value, the switch module is controlled to be turned off.

[0090] In another possible implementation, the safety current value is the maximum impact current value of the switch module, or the safety current value is the current value corresponding to the second time point, the second time point is the time point in the current parameter periodic curve corresponding to the switch module, the time point when the first current parameter drops to zero minus the delay time and the withstand time, the delay time is the time from the moment when the shutdown signal is sent to the switch module to the moment when the switch module is actually shut down, the withstand time is the time from the moment when the first current parameter shows a downward trend, the maximum impact current value is greater than zero.

[0091] Specifically, when the relay in the switch module has electrical resistance, the safety current value can be the maximum impact current value determined according to the electrical resistance of the switch module. In addition, when there is a non-negligible delay time in the shutdown process of the switch module, the safety current value is based on the current value corresponding to the time point of the maximum impact current value minus the delay time when the first current parameter in the current parameter cycle curve of the switch module shows a downward trend.

[0092] The preset duration is the sum of the first duration when the current value of the switch module is zero and twice the withstand time. The withstand time is the withstand time between the moment corresponding to the maximum withstand current value of the switch module and the moment when the first current parameter drops to zero when the first current parameter shows a downward trend.

[0093] Therefore, the switch module is controlled to be turned off at any moment within the preset time period from when the first current parameter is less than or equal to the safe current value of the switch module. Specifically, the switch module is controlled to be turned off within the preset time period of the sum of the first time period from when the current parameter of the switch module is less than or equal to the safe current value to when the current value of the switch module is zero and twice the withstand time period. The withstand time period is the withstand time period between the time point corresponding to the maximum withstand current value of the switch module and the time point when the current value drops to zero when the first current parameter shows a downward trend.

[0094] The maximum impact current withstand value of the switch module is determined based on the maximum impact current withstand value of the relay switch in the switch module. If there are multiple relay switches in the switch module, the maximum impact current withstand value of the switch module is determined based on the minimum value of the maximum impact current withstand values of all relay switches in the switch module.

[0095] The above consideration that the switch module has a certain current resistance capability further expands the time range for the switch module to achieve shutdown, and also further increases the current range of the controller to control the switch module to shut down, giving the relay body a longer shutdown time range, which can better adapt to the time consumed by the shutdown process. At the same time, the time range for the controller to perform shutdown control can be expanded, further reducing the situation of waiting for the next cycle to shut down, which also reduces the switch from being subjected to another large current impact while waiting for the next cycle.

[0096] In addition, when the above-mentioned switch module does not consider the electrical resistance and the delay time of the switch module shutdown can be ignored, the safety current value is zero; after the inverter circuit completes the wave sealing, the controller is also used to, in response to the change trend of the first current parameter being a downward trend, control the switch module to shut down within a preset time length of the first time length when the first current parameter of the switch module is zero after the first current parameter of the switch module is collected to be zero. It should be noted that when collecting the first current parameter when the first current parameter is in a downward trend, the actual collection point when the first current parameter of the switch module is collected to be zero should be collected as close as possible to the target time point when the first current parameter first drops to zero during the downward process (for example, see Figure 3 Therefore, when the first current parameter is collected and shows a downward trend and is close to zero, the collection time interval can be shortened to ensure that the time interval between the actual collection point and the target time point is within an acceptable time interval range.

[0097] See also Figure 3 As shown, the first duration when the current value of the switch module is zero is Figure 3 The duration between T1 and T4, specifically, the calculation formula of the first duration is:

[0098]

[0099] Wherein, ΔT is the first time length between the moment when the current parameter of the switch module is zero and the moment when the voltage value of the most recent switch module is zero when the current parameter of the switch module is in a downward trend. U is the rated voltage value of the phase power corresponding to the switch module, V is the voltage value of the phase power corresponding to the switch module, and f is the frequency of the phase power corresponding to the switch module.

[0100] Based on the above embodiment, when the safety current value is greater than 0, after the response that the first current parameter of the switch module at the current moment is less than or equal to the safety current value of the switch module, the controller can also be used to determine whether the first current parameter is less than or equal to a preset safety value; wherein the preset safety value is less than the safety current value; when the first current value parameter is less than or equal to the preset safety value, the switch module is controlled to be turned off.

[0101] When the first current value parameter is detected to be less than or equal to the preset safety value, regardless of whether the current cycle curve is in the rising curve stage or the falling curve stage, after the controller sends a shutdown signal to the switch module, even after the delay period, it can ensure that the switch module is shut down within the safe current value range. Therefore, when the relay switch in the switch module has a certain ability to withstand inrush current, when the first current value is less than or equal to the second preset current value, the switch module can be directly controlled to shut down without the need to monitor the current change trend of the switch module. The preset safety value can be the current value determined at the time point corresponding to the maximum inrush current value of the switch module in the curve of the downward trend of the current parameter cycle curve of the switch module, after adding the delay period, and the preset safety value must be greater than zero.

[0102] When the inverter outputs three-phase electricity, if only one phase is short-circuited, the remaining two phases will form a loop with the grid and the load, which may easily lead to abnormal current in the remaining two phases. Figure 5 The middle dotted line indicates that after the phase A relay is cut off, capacitor C1 is cut off, while capacitors C2 and C3 are not cut off and form a loop with the grid and load connected to the output end of the inverter circuit, resulting in abnormal current in the remaining two phases. Alternatively, see Figure 6 , multiple DC sources of power (such as photovoltaic panels, see Figure 6 Machine 1 and machine 2 in the figure are connected to the grid in parallel through the corresponding inverter circuit. When the current of machine 2 is disconnected, the current i A The corresponding A-phase relay and capacitor C4 are cut off, and the current of machine 1 forms a loop through C5 and C6 and the two-phase switch module of the faulty machine 2 that is not disconnected (see Figure 6 The dotted line in the figure shows the current i B 、i C In summary, three-phase imbalance can easily lead to phase current disorder, and it is difficult to accurately identify the zero-current shutdown timing of the other two-phase relays. Therefore, for the three-phase power inverter circuit, this application proposes that the three-phase power inverter circuit can be used to simultaneously cut off multiple corresponding relays and no longer use the above loop, which can effectively avoid the problem of three-phase imbalance in the grid line voltage. The specific implementation method can be as follows:

[0103] The inverter circuit is set to output three-phase electricity, and the controller is also used to:

[0104] Before controlling the switch module corresponding to the first current parameter to turn off, determine that among the three switch modules corresponding to the three phases of electricity, except the switch module corresponding to the phase of electricity corresponding to the first current parameter, the switch modules corresponding to the first current parameter in the other two switch modules are completed to turn off, and the switch modules whose current parameters are less than or equal to the threshold value; while controlling the switch module corresponding to the first current parameter to turn off, the switch modules whose current parameters are less than or equal to the threshold value are controlled to turn off.

[0105] See also Figure 5 , Figure 5 The negative pole of the DC source is short-circuited to the ground. The current value collected in the short-circuit loop is positive. Therefore, the current parameter can be directly taken as the current value. According to the current cycle curve of the three-phase electricity, it is determined that when the A-phase switch module is turned off, the transmission current i B Phase B switch module and transmission current i c The current of the C-phase switch module is less than or equal to the threshold switch module. For example, the threshold is set to 0, see Figure 5 In the embodiment, if the A-phase switch module is finally turned off at T1, the current of the corresponding C-phase switch module is 0, while the current of the B-phase switch module is greater than zero. Therefore, when the A-phase switch module is controlled to be turned off at T1, the C-phase switch module can be turned off at the same time.

[0106] Furthermore, in a possible implementation, the threshold value may be 0, and the switch module whose current parameter is less than or equal to the threshold value may also be a switch module whose current parameter is zero at the moment when the first current parameter drops to zero, for example, see Figure 3 The time point when the first current parameter of the A-phase switch module drops to zero is collected (see Figure 3 At the T1 moment in the figure), the C-phase switch module has a current parameter of zero, so that the A-phase switch module and the C-phase switch module are simultaneously shut down at zero current, thereby improving safety.

[0107] Furthermore, the time range allowed for controlling the simultaneous shutdown of the multiple switch modules is expanded by combining the duration of the zero current of the multiple switch modules that simultaneously achieve zero current shutdown (for example, see Figure 3 The time range for realizing zero-current shutdown of the A-phase switch module and the C-phase switch module is from time point T1 to time point T3). Specifically, the controller is used to control the shutdown of the switch module corresponding to the first current parameter and the shutdown of the switch module whose second current value is zero within a set time period starting from when the first current parameter is less than or equal to the safe current value of the switch module corresponding to the first current parameter.

[0108] The calculation formula for the above set duration is:

[0109]

[0110] Wherein, ΔT is the case where the first current parameter is in a downward trend, and the first current parameter is

[0111] The frequency of the transmitted phase power.

[0112] Based on the above embodiment, there are multiple possible ways to determine the variation trend of the first current parameter of the switch module, which may be as follows:

[0113] In one possible implementation, for the switch module, multiple first current parameters are continuously collected starting from the current moment, and the change trend of the multiple first current parameters over time is determined according to the collection time as the first current parameter change trend of the switch module corresponding to the current moment.

[0114] In another possible implementation, based on the first current parameter of the switch module recorded before the current moment, a change trend of the first current parameter of the switch module corresponding to the current moment is determined.

[0115] Exemplarily, the inverter can be provided with an acquisition circuit, etc., and can collect and record the first current parameter of the switch module according to a preset interval length (the acquisition interval length can be fixed or not. Exemplarily, the interval length is determined according to the phase frequency or period of the inverter circuit. For example, if the phase frequency is 50 Hz and the period is 0.02S, the interval length can be one twentieth of the period length, that is, 0.001S. Ensure that multiple acquisitions can determine the change trend of the current parameter). When it is determined that the first current parameter of the switch module at the current moment is less than or equal to the safe current value, the first current parameter of one or more consecutive historical records of the switch module recorded before the current moment can be retrieved. According to the first current parameter of the historical record and the current first current parameter, the change trend of the first current parameter of the switch module at the current moment is determined. If the current parameter gradually decreases over time, the current change trend is a downward trend, otherwise it is an upward trend.

[0116] In another possible implementation, after waiting for a specified period of time starting from the current moment, the first current parameter of the switch module is reacquired, and the current parameter change trend of the switch module is determined based on the magnitude relationship between the two first current parameters before and after the waiting for the specified period of time.

[0117] Exemplarily, the specified waiting time can be determined based on the phase frequency or cycle of the inverter circuit. For example, if the phase frequency is 50 Hz and the cycle is 0.02S, the specified waiting time can be one twentieth of the cycle, that is, 0.001S. Of course, it can also be determined based on human experience.

[0118] Based on the magnitude relationship between the first current parameter before waiting for the specified time period and the first current parameter after waiting for the specified time period, the current change trend of the switch module is determined. If the first current parameter before waiting for the specified time period is greater than the first current parameter after waiting for the specified time period, it can be determined that the current parameter change trend of the switch module is a downward trend.

[0119] Furthermore, based on the above embodiment, the controller is further configured to, in response to a relay shutdown command, control the switch module to shut down at zero current in the event of a power outage in the inverter circuit. Regardless of the aforementioned ground short-circuit abnormality, the switch module can be controlled to shut down at zero current, thereby preventing current shock to the relay and improving safety.

[0120] The topology of the inverter may be one of NPC, TNPC, HERIC and ANPC.

[0121] The switch module can include at least two relay switches, each with a control terminal connected to the controller. When the switch module is controlled to shut down, one of the relay switches in the switch module can be controlled to shut down. Multiple relays in the switch module provide redundancy. Each time a short-circuit to ground is disconnected, multiple relays in the switch module can be alternately disconnected, avoiding the need to repeatedly use the same relay for shutdown. This reduces the number of times the relays are subjected to current surges, increases relay life, and reduces the need for replacement and maintenance.

[0122] The above are some specific implementations of an inverter provided by the embodiment of the present application. Based on this, the present application also provides a corresponding method. The following will introduce the device provided by the embodiment of the present application from the perspective of the method.

[0123] See also Figure 4 A flow chart of a method for shutting down an inverter is shown. The method for shutting down an inverter includes: an inverter circuit, a switch module, and a controller. The input end of the inverter circuit is connected to a DC source, the output end of the inverter circuit is connected to the switch module, and the output end of the switch module is used to connect to a power grid. The method further includes:

[0124] S401, in response to a short circuit to ground fault, performing wave blocking processing on the inverter circuit;

[0125] S402: After the inverter circuit completes wave sealing, in response to the first current parameter of the switch module at the current moment being less than or equal to the safety current value of the switch module, determining a change trend of the first current parameter of the switch module corresponding to the current moment, the safety current value being greater than zero;

[0126] When the change trend of the first current parameter is a downward trend, the switch module is controlled to be turned off.

[0127] According to the above method, based on the safe current value and combined with the current change trend of the switch module, it is monitored and analyzed whether the switch module can be safely shut down, avoiding the relay from being subjected to large current shocks and improving the stability of the circuit.

[0128] The above-mentioned DC source may be a photovoltaic string.

[0129] In a possible implementation, when the change trend of the first current parameter is a downward trend, controlling the switch module to turn off includes:

[0130] In response to the changing trend of the first current parameter being a downward trend, the switch module is controlled to be turned off; or, in response to the changing trend of the first current parameter being a downward trend, the switch module is controlled to be turned off at any moment within a preset time period from when the first current parameter is less than or equal to the safe current value of the switch module.

[0131] In a possible implementation, the inverter circuit includes an upper half bridge arm and a lower half bridge arm;

[0132] The performing wave sealing processing on the inverter circuit includes:

[0133] Turn off the driving of each switch tube in the upper half bridge arm and the lower half bridge arm; or,

[0134] When the short-circuit fault to ground is caused by a short circuit between the negative electrode of the DC source and the ground, and the withstand current of each switch in the lower half bridge arm is greater than the maximum short-circuit current of the short circuit between the negative electrode of the DC source and the ground, turning off the driving of each switch in the upper half bridge arm;

[0135] When the short-circuit fault to ground is caused by a short circuit between the positive electrode of the DC source and the ground, and the withstand current of each switch tube in the upper half bridge arm is greater than the maximum short-circuit current of the short circuit between the positive electrode of the DC source and the ground, the driving of each switch tube in the lower half bridge arm is turned off.

[0136] In one possible implementation, the safe current value is a current value corresponding to a first time point, where the first time point is a periodic time point determined by subtracting a delay time from a time point at which the first current parameter drops to zero in a current parameter periodic curve corresponding to the switch module. The delay time is the time from when a shutdown signal is sent to the switch module to when the switch module is actually shut down.

[0137] The preset duration is a first duration during which the first current parameter value of the switch module is zero.

[0138] In a possible implementation, the safety current value is the maximum impact current value of the switch module, or the safety current value is the current value corresponding to a second time point, the second time point is a periodic time point determined by subtracting a delay time and a withstand time from a time point when the first current parameter drops to zero in a current parameter periodic curve corresponding to the switch module, the delay time is the time from the moment when a shutdown signal is sent to the switch module to the moment when the switch module is actually shut down, the withstand time is the time from the moment when the first current parameter shows a downward trend to the moment when the maximum impact current value of the switch module corresponds to the first current parameter drops to zero, and the maximum impact current value is greater than zero;

[0139] The preset time length is the sum of the first time length when the current value of the switch module is zero and twice the power-withstanding time length.

[0140] In one possible implementation, the safety current value is zero; after the inverter circuit completes wave sealing, it also includes: in response to the change trend of the first current parameter being a downward trend, after the first current parameter of the switch module is collected to be zero, the switch module is controlled to be turned off within a preset time length of the first time length when the first current parameter of the switch module is zero.

[0141] Furthermore, the calculation formula for the first duration is:

[0142]

[0143] Wherein, ΔT is the first time length between the moment when the current parameter of the switch module is zero and the moment when the voltage value of the most recent switch module is zero when the current parameter of the switch module is in a downward trend. U is the rated voltage value of the phase power corresponding to the switch module, V is the voltage value of the phase power corresponding to the switch module, and f is the frequency of the phase power corresponding to the switch module.

[0144] In a possible implementation, the safety current value is greater than 0, and after responding that the first current parameter of the switch module at the current moment is less than or equal to the safety current value of the switch module, the method further includes:

[0145] Determining whether the first current parameter is less than or equal to a preset safety value; wherein the preset safety value is less than the safe current value;

[0146] When the first current value parameter is less than or equal to the preset safety value, the switch module is controlled to be turned off.

[0147] In one possible implementation, the inverter circuit outputs three phases of electricity. Before controlling the switch module corresponding to the first current parameter to shut down, the method further includes: determining that among the three switch modules corresponding to the three phases of electricity, except the switch module corresponding to the first current parameter, the switch modules corresponding to the first current parameter in the other two switch modules complete the shutdown, and the current parameters are less than or equal to the threshold; while controlling the switch module corresponding to the first current parameter to shut down, the switch module with the current parameter less than or equal to the threshold is controlled to shut down.

[0148] Optionally, the switch module whose current parameter is less than or equal to the threshold is a switch module whose current parameter is zero at the moment when the first current parameter drops to zero;

[0149] The method of controlling the switch module corresponding to the first current parameter to be turned off and simultaneously controlling the switch module having a current value less than or equal to a threshold to be turned off includes:

[0150] Within a set time period starting from when the first current parameter is less than or equal to the safe current value of the switch module, the switch module corresponding to the first current parameter is controlled to be turned off while the switch module with the second current value of zero is controlled to be turned off.

[0151] The calculation formula for the above set duration is:

[0152]

[0153] Wherein, ΔT is the first time length between the time point when the first current parameter is zero and the time point when the most recent voltage value is zero when the first current parameter is in a downward trend. f is the frequency of the phase power transmitted by the switching module corresponding to the first current parameter.

[0154] In a possible implementation, determining a change trend of the first current parameter of the switch module corresponding to a current moment includes:

[0155] For the switch module, continuously collect multiple first current parameters starting from the current moment, and determine the change trends of the multiple first current parameters according to the collection time as the first current parameter change trend of the switch module corresponding to the current moment; or,

[0156] Determine a change trend of the first current parameter of the switch module corresponding to the current moment based on the first current parameter of the switch module recorded before the current moment; or

[0157] After waiting for a specified time period starting from the current moment, the first current parameter of the switch module is reacquired, and a current parameter change trend of the switch module is determined based on a magnitude relationship between the two first current parameters before and after the waiting for the specified time period.

[0158] In a possible implementation, the method further includes: in response to a relay shut-off instruction, controlling the switch module to shut down at a zero current moment when the inverter circuit is blocked.

[0159] Optionally, the topology of the inverter circuit is one of NPC, TNPC, HERIC and ANPC.

[0160] Optionally, the switch module includes at least two relay switches, and a control end of each relay switch is connected to the controller;

[0161] The controlling the switch module to turn off includes:

[0162] Control a relay switch in the switch module to turn off.

[0163] In addition, the present application also provides a photovoltaic system, including a photovoltaic string and an inverter, wherein the photovoltaic string is connected to the input end of the inverter to provide direct current to the inverter; the output end of the inverter is connected to the power grid to convert direct current into alternating current and transmit it to the power grid, and the inverter is the inverter described in any of the above embodiments, and / or the inverter applying the above method.

[0164] The embodiments of the present application also provide corresponding devices and computer storage media for implementing the solutions provided by the embodiments of the present application.

[0165] The device includes a memory and a processor, the memory is used to store instructions or codes, and the processor is used to execute the instructions or codes so that the device executes an inverter shutdown method described in any embodiment of the present application.

[0166] The computer storage medium stores code. When the code is executed, a device executing the code implements an inverter shut-down method described in any embodiment of the present application.

[0167] The "first" and "second" (if any) in the names mentioned in the embodiments of this application are only used as name identifiers and do not mean the first or second in order.

[0168] Through the description of the above embodiments, it can be known that those skilled in the art can clearly understand that all or part of the steps in the above embodiment methods can be implemented by means of software plus a general hardware platform. Based on this understanding, the technical solution of the present application can be embodied in the form of a software product, which can be stored in a storage medium, such as a read-only memory (ROM) / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network communication device such as a router) to execute the methods described in each embodiment or certain parts of the embodiments of the present application.

[0169] Each embodiment in this specification is described in a progressive manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple. For the relevant parts, refer to the partial description of the method embodiment. Some or all of the modules can be selected according to actual needs to achieve the purpose of the embodiment. Those of ordinary skill in the art can understand and implement it without paying any creative work.

[0170] The above description is merely an exemplary embodiment of the present application and is not intended to limit the scope of protection of the present application.

Claims

1. An inverter, characterized in that: include: An inverter circuit, a switch module, and a controller, wherein the input of the inverter circuit is connected to a DC source, the output of the inverter circuit is connected to the switch module, and the output of the switch module is used to connect to a power grid; the controller is used to: In response to a short-circuit fault to ground, performing a wave blocking process on the inverter circuit; After the inverter circuit completes wave sealing, in response to the first current parameter of the switch module at a current moment being less than or equal to the safety current value of the switch module, determining a change trend of the first current parameter of the switch module corresponding to the current moment, the safety current value being greater than zero; When the change trend of the first current parameter is a downward trend, the switch module is controlled to be turned off.

2. The inverter according to claim 1, characterized in that When the change trend of the first current parameter is a downward trend, controlling the switch module to turn off includes: When the change trend of the first current parameter is a downward trend, controlling the switch module to be turned off; or, When the change trend of the first current parameter is a downward trend, the switch module is controlled to be turned off at any moment within a preset time period starting from when the first current parameter is less than or equal to the safe current value of the switch module.

3. The inverter according to claim 1, characterized in that The inverter circuit includes an upper half bridge arm and a lower half bridge arm; The performing wave sealing processing on the inverter circuit includes: Turn off the driving of each switch tube in the upper half bridge arm and the lower half bridge arm; or, When the short-circuit fault to ground is caused by a short circuit between the negative electrode of the DC source and the ground, and the withstand current of each switch in the lower half bridge arm is greater than the maximum short-circuit current of the short circuit between the negative electrode of the DC source and the ground, turning off the driving of each switch in the upper half bridge arm; When the short-circuit fault to ground is caused by a short circuit between the positive electrode of the DC source and the ground, and the withstand current of each switch tube in the upper half bridge arm is greater than the maximum short-circuit current of the short circuit between the positive electrode of the DC source and the ground, the driving of each switch tube in the lower half bridge arm is turned off.

4. The inverter according to claim 2, characterized in that: The safe current value is a current value corresponding to a first time point, which is a periodic time point determined by subtracting a delay time from the time when the first current parameter drops to zero in the current parameter periodic curve corresponding to the switch module. The delay time is the time from the time when the shutdown signal is sent to the switch module to the time when the switch module is actually shut down. The preset duration is a first duration during which the first current parameter value of the switch module is zero.

5. The inverter according to claim 2, characterized in that: The safety current value is the maximum impact current value of the switch module, or the safety current value is the current value corresponding to a second time point, the second time point is a periodic time point determined by subtracting the delay time and the withstand time from the time when the first current parameter drops to zero in the current parameter periodic curve corresponding to the switch module, the delay time is the time from the time when the shutdown signal is sent to the switch module to the time when the switch module is actually shut down, the withstand time is the time from the time point corresponding to the maximum impact current value of the switch module to the time point when the first current parameter shows a downward trend, and the maximum impact current value is greater than zero; The preset time length is the sum of the first time length when the current value of the switch module is zero and twice the power-withstanding time length.

6. The inverter according to claim 2, characterized in that: The safety current value is zero; after the inverter circuit completes the wave sealing, the controller is further used to: In response to the first current parameter changing in a downward trend, after the first current parameter of the switch module is collected to be zero, the switch module is controlled to be turned off within a preset time duration of the first time duration when the first current parameter of the switch module is zero.

7. The inverter according to claim 2, characterized in that: The safety current value is greater than 0, and after the first current parameter of the switch module at the current moment is less than or equal to the safety current value of the switch module, the method further includes: Determining whether the first current parameter is less than or equal to a preset safety value; wherein the preset safety value is less than the safe current value; When the first current value parameter is less than or equal to the preset safety value, the switch module is controlled to be turned off.

8. The inverter according to claim 1, characterized in that The inverter circuit outputs three-phase electricity, and the controller is further used to: Before controlling the switch module corresponding to the first current parameter to turn off, determine that among the three switch modules corresponding to the three phases of electricity, except the switch module corresponding to the phase of electricity corresponding to the first current parameter, the switch modules corresponding to the first current parameter in the other two switch modules are completed to turn off, and the switch modules whose current parameters are less than or equal to the threshold value; while controlling the switch module corresponding to the first current parameter to turn off, the switch modules whose current parameters are less than or equal to the threshold value are controlled to turn off.

9. The inverter according to claim 8, characterized in that: The switch module whose current parameter is less than or equal to the threshold is a switch module whose current parameter is zero at the moment when the first current parameter drops to zero; When controlling the switch module corresponding to the first current parameter to be turned off and simultaneously controlling the switch module having a current value less than or equal to the threshold to be turned off, the controller is configured to: Within a set time period starting from when the first current parameter is less than or equal to the safe current value of the switch module, the switch module corresponding to the first current parameter is controlled to be turned off while the switch module with the second current value of zero is controlled to be turned off.

10. The inverter according to claim 1, characterized in that The determining of a change trend of a first current parameter of the switch module corresponding to a current moment includes: For the switch module, continuously collect multiple first current parameters starting from the current moment, and determine the change trends of the multiple first current parameters according to the collection time as the first current parameter change trend of the switch module corresponding to the current moment; or, Determine a change trend of the first current parameter of the switch module corresponding to the current moment based on the first current parameter of the switch module recorded before the current moment; or After waiting for a specified time period starting from the current moment, the first current parameter of the switch module is reacquired, and a current parameter change trend of the switch module is determined based on a magnitude relationship between the two first current parameters before and after the waiting for the specified time period.

11. The inverter according to claim 1, characterized in that: The controller is further configured to control the switch module to be turned off at a zero current moment in response to a relay turn-off instruction when the inverter circuit is blocked.

12. The inverter according to claim 1, characterized in that The switch module includes at least two relay switches, and the control end of each relay switch is connected to the controller; The controlling the switch module to turn off includes: Control a relay switch in the switch module to turn off.

13. The inverter according to claim 1, characterized in that The DC source is a photovoltaic string.

14. A method for shutting down an inverter, characterized in that: The inverter includes: an inverter circuit, a switch module, and a controller. The input end of the inverter circuit is connected to a DC source, the output end of the inverter circuit is connected to the switch module, and the output end of the switch module is used to connect to a power grid. The method includes: In response to a short-circuit fault to ground, performing a wave blocking process on the inverter circuit; After the inverter circuit completes wave sealing, in response to the first current parameter of the switch module at a current moment being less than or equal to the safety current value of the switch module, determining a change trend of the first current parameter of the switch module corresponding to the current moment, the safety current value being greater than zero; When the change trend of the first current parameter is a downward trend, the switch module is controlled to be turned off.

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