Voltage control methods, detection methods, and inverters

Abstract

This application relates to a voltage control method, a detection method, and an inverter. The voltage control method includes: acquiring the wiring configuration between the inverter and the power grid while multiple relays are in a detection state; determining a current control strategy for the inverter circuit based on the wiring configuration and the current three-phase grid voltage, where the current control strategy includes either a three-phase coupled control mode or a three-phase independent control mode; controlling the inverter circuit to output a three-phase drive voltage, which serves as the three-phase inverter voltage, based on the current control strategy and the three-phase grid voltage; and determining a first state of the relays based on the three-phase grid voltage and the three-phase inverter voltage, where the first state includes a normal operating state and a fault state. This method avoids excessive voltage difference between the three-phase inverter voltage and the three-phase grid voltage, preventing excessive inrush current during relay activation in the switching circuit, which could affect the relay's lifespan.

Description

Technical Field

[0001] This application relates to the field of new energy power generation technology, and in particular to a voltage control method, a detection method, and an inverter. Background Technology

[0002] The inverter side of the grid-connected inverter, where the inverter circuit is located, is isolated from the grid side where the grid is located through a relay. Before the grid-connected inverter is connected to the grid, the relay needs to be self-tested to ensure that the relay can work normally.

[0003] In existing technologies, relay self-testing is performed by comparing the three-phase inverter voltage on the inverter side with the three-phase grid voltage on the grid side. When the three-phase grid voltage harmonics are high, the relay self-testing process generates a large inrush current, affecting the relay's lifespan and reducing the lifespan of the grid-connected inverter. Summary of the Invention

[0004] Therefore, it is necessary to provide a voltage control method, a detection method, and an inverter to avoid the problem of excessive inrush current affecting the lifespan of the relay during the relay self-test process.

[0005] A voltage control method is applied to an inverter, the inverter including an inverter circuit and a switching circuit, the switching circuit including a plurality of relays respectively connected to the inverter circuit and the power grid; the voltage control method includes:

[0006] When the multiple relays are in the detection state, the wiring method between the inverter and the power grid is obtained;

[0007] Based on the wiring method and the current three-phase grid voltage, a current control strategy for controlling the inverter circuit is determined. The current control strategy includes one of a three-phase coupled control mode and a three-phase independent control mode.

[0008] Based on the current control strategy and the three-phase grid voltage, the inverter circuit is controlled to output a three-phase drive voltage, which serves as the three-phase inverter voltage of the inverter.

[0009] The first state of the relay is determined based on the three-phase grid voltage and the three-phase inverter voltage, and the first state includes a normal operating state and a fault state.

[0010] In one embodiment, determining the current control strategy for controlling the inverter circuit based on the wiring configuration and the current three-phase grid voltage includes:

[0011] When the wiring system is a four-wire system, the maximum imbalance of the three-phase grid voltage is obtained based on the current three-phase grid voltage.

[0012] If the maximum imbalance is less than or equal to the first threshold, the current control strategy is determined to be the three-phase coupling control mode;

[0013] If the maximum imbalance is greater than the first threshold, the current control strategy is determined to be the three-phase independent control mode.

[0014] In one embodiment, the voltage control method further includes:

[0015] When the wiring method is a three-wire system, the current control strategy is determined to be the three-phase coupling control method.

[0016] In one embodiment, controlling the inverter circuit to output a three-phase drive voltage according to the current control strategy and the three-phase grid voltage includes:

[0017] When the current control strategy is the three-phase coupling control mode, a first three-phase pulse modulation signal is obtained based on the three-phase grid voltage and the preset d-axis voltage to control the inverter circuit to output the three-phase drive voltage.

[0018] In one embodiment, obtaining the first three-phase pulse modulation signal based on the three-phase grid voltage and the preset d-axis voltage includes:

[0019] Based on the three-phase grid voltage, the q-axis voltage and rotation angle of the dq coordinate system are obtained;

[0020] The first three-phase pulse modulation signal is obtained based on the q-axis voltage, the rotation angle, and the preset d-axis voltage.

[0021] In one embodiment, controlling the inverter circuit to output a three-phase drive voltage according to the current control strategy and the three-phase grid voltage includes:

[0022] When the current control strategy is the three-phase independent control mode, the first three-phase pulse modulation signal corresponding to the grid voltage of each phase in the three-phase grid voltage and the first modulation ratio coefficient are obtained to control the inverter circuit to output the three-phase drive voltage.

[0023] In one embodiment, controlling the inverter circuit to output a three-phase drive voltage according to the current control strategy and the three-phase grid voltage includes:

[0024] Based on the current control strategy, the three-phase grid voltage, the inverter current of each phase in the current three-phase inverter current of the inverter circuit, and the second modulation ratio coefficient, the inverter circuit is controlled to output the three-phase drive voltage.

[0025] In one embodiment, controlling the inverter circuit to output the three-phase drive voltage based on the current control strategy, the three-phase grid voltage, the inverter current of each phase in the current three-phase inverter current of the inverter circuit, and the second modulation ratio coefficient includes:

[0026] Based on the current control strategy and the three-phase grid voltage, the first three-phase pulse modulation signal corresponding to the three-phase grid voltage is obtained;

[0027] The second three-phase pulse modulation signal is obtained based on the inverter current of each phase and the second modulation ratio coefficient.

[0028] The inverter circuit is controlled to output the three-phase drive voltage according to the first three-phase pulse control signal and the second three-phase pulse control signal.

[0029] A detection method is applied to an inverter, the inverter including an inverter circuit and a switching circuit, the switching circuit including a plurality of relays respectively connected to the inverter circuit and the power grid; the detection method includes:

[0030] When the multiple relays are in the open state, the inverter circuit is controlled to output a three-phase drive voltage according to the voltage control method described above, which serves as the three-phase inverter voltage of the inverter.

[0031] When the multiple relays are in the on state and the inverter circuit stops working, the three-phase output voltage at the output terminal of the inverter is obtained as the three-phase inverter voltage;

[0032] The first state of the relay is determined based on the three-phase inverter voltage and the three-phase grid voltage.

[0033] In one embodiment, determining the first state of the relay based on the three-phase inverter voltage and the three-phase grid voltage includes:

[0034] The first voltage difference is obtained based on the three-phase drive voltage output by the inverter circuit and the three-phase grid voltage;

[0035] When the inverter stops working, a second voltage difference is obtained based on the three-phase inverter voltage and the three-phase grid voltage.

[0036] If the first voltage difference is less than the first voltage threshold and the second voltage difference is less than the second voltage threshold, the relay is determined to be in normal operating condition.

[0037] In one embodiment, the detection method further includes:

[0038] When the inverter circuit outputs a three-phase drive voltage, in response to the current three-phase inverter current of the inverter and the second state of the plurality of relays satisfying a preset condition, the plurality of relays are controlled to be in an open state, and the inverter circuit is controlled to stop working; wherein, the second state includes an open state and an on state.

[0039] In one embodiment, the step of controlling the plurality of relays to be in an open state and controlling the inverter circuit to stop working in response to the current three-phase inverter current of the inverter and the second state of the plurality of relays satisfying a preset condition includes:

[0040] When each of the relays is in the conducting state and the absolute value of the inverter current of each phase in the three-phase inverter current is greater than the first preset current, it is determined that the three-phase inverter current and the second state of the relays satisfy the preset condition.

[0041] When the relay is in the open state and at least one of the absolute values ​​of the inverter currents of each phase is at a second threshold, it is determined that the three-phase inverter currents and the second state of the relay satisfy the preset condition.

[0042] In one embodiment, the detection method further includes: when the relay is in the open state and the absolute value of the inverter current of each phase is less than the second threshold, obtaining the first preset current based on the maximum and minimum values ​​of the absolute values ​​of the inverter current of each phase.

[0043] An inverter, comprising:

[0044] Inverter circuit;

[0045] A switching circuit, the switching circuit including a plurality of relays respectively connected to the inverter circuit and the power grid;

[0046] A controller, which is used to implement the steps of the voltage control method described above, or to implement the steps of the detection method described above.

[0047] In the above voltage control method, based on the wiring configuration between the inverter and the power grid, and the current three-phase grid voltage, the current control strategy for controlling the inverter circuit is determined in both the three-phase coupling control mode and the three-phase independent control mode. Based on the current control strategy and the three-phase grid voltage, the inverter circuit output is controlled to serve as the three-phase drive voltage for the three-phase inverter voltage. This avoids excessive voltage difference between the three-phase inverter voltage and the three-phase grid voltage, which could lead to excessive inrush current during relay energization in the switching circuit, affecting relay lifespan, reducing half-bus voltage imbalance, and improving inverter lifespan.

[0048] In the above detection method, when multiple relays are in the open state, the current control strategy for controlling the inverter circuit is determined based on the wiring method between the inverter and the power grid, and the current three-phase grid voltage. This involves using either the three-phase coupled control mode or the three-phase independent control mode. Based on the current control strategy and the three-phase grid voltage, the inverter circuit output is controlled to serve as the three-phase drive voltage for the three-phase inverter. This avoids excessive voltage difference between the three-phase inverter voltage and the three-phase grid voltage during relay detection, preventing excessive inrush current during relay activation in the switching circuit, which could affect relay lifespan. It also reduces half-bus voltage imbalance and improves the inverter's lifespan. When multiple relays are in the closed state and the inverter circuit is not operating, the three-phase output voltage at the inverter's output terminal is obtained as the three-phase inverter voltage. Based on the three-phase inverter voltage and the three-phase grid voltage, the first state of the relays can be determined, thus enabling relay detection within the inverter. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the inverter structure in an embodiment of this application;

[0051] Figure 2 This is a flowchart illustrating the voltage control method in an embodiment of this application;

[0052] Figure 3 This is a flowchart illustrating the process of determining the current control strategy for the inverter circuit based on the wiring configuration and the current three-phase grid voltage in an embodiment of this application.

[0053] Figure 4 This is one of the control block diagrams for obtaining the first three-phase pulse modulation signal based on the three-phase grid voltage and the preset shaft voltage in the embodiments of this application;

[0054] Figure 5 This is the second control block diagram in the embodiments of this application for obtaining the first three-phase pulse modulation signal based on the three-phase grid voltage and the preset shaft voltage;

[0055] Figure 6 This is a schematic diagram of the process for controlling the output of the three-phase drive voltage of the inverter circuit in an embodiment of this application;

[0056] Figure 7 This is a control block diagram for obtaining the second three-phase pulse modulation signal based on the inverter current of each phase and the second modulation ratio coefficient in an embodiment of this application.

[0057] Figure 8 This is one of the flowcharts illustrating the detection method in this embodiment of the disclosure;

[0058] Figure 9 This is a flowchart illustrating the process of determining the first state of the relay based on the three-phase inverter voltage and the three-phase grid voltage in an embodiment of this application.

[0059] Figure 10 This is a second schematic flowchart of the detection method in the embodiments of this application;

[0060] Figure 11 Examples of embodiments in this application Figure 10 A flowchart of S602;

[0061] Figure 12 Examples of embodiments in this application Figure 10 A flowchart of S604;

[0062] Figure 13 Examples of embodiments in this application Figure 10 A flowchart of the S606 process;

[0063] Figure 14 Examples of embodiments in this application Figure 10 A flowchart of the S608 process;

[0064] Figure 15 Examples of embodiments in this application Figure 10 A flowchart of the S610 process;

[0065] Figure 16 This is the third schematic flowchart of the detection method in the embodiments of this disclosure;

[0066] Figure 17 This is a schematic diagram of the inverter structure in an embodiment of this application.

[0067] Explanation of reference numerals in the attached figures:

[0068] Inverter 100; Inverter circuit 102; Switching circuit 104; First part 1041; Second part 1042; Controller 106; Relay 202; Power grid 200; Acquisition module 302; Selection module 304; Control module 306; Control module 400. Detailed Implementation

[0069] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0071] It is understood that the terms "first," "second," etc., used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first pressure differential may be referred to as a second pressure differential, and similarly, a second pressure differential may be referred to as a first pressure differential.

[0072] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0073] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0074] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0075] In this embodiment, a voltage control method is provided, which is applied to an inverter. The inverter includes an inverter circuit and a switching circuit. The switching circuit includes multiple relays, which are respectively connected to the inverter circuit and the power grid. By controlling the second state of the multiple relays, the parallel connection and disconnection of the inverter side where the inverter circuit is located and the power grid side where the power grid is located can be realized.

[0076] Figure 1 This is a schematic diagram of the inverter structure in an embodiment of this application, as shown below. Figure 1As shown, the inverter 100 includes an inverter circuit 102 and a switching circuit 104. The switching circuit 104 includes a plurality of relays 202. As an example, the plurality of relays 202 include a first part 1041 and a second part 1042 connected in series. The first part 1041 is connected to the inverter circuit 102, and the second part 1042 is connected to the power grid 200. By dividing the plurality of relays 202 into a first part 1041 and a second part 1042 connected in series, the purpose of safety redundancy is achieved.

[0077] As an example, the number of relays 202 in the first part 1041 and the second part 1042 is the same. Furthermore, both the first part 1041 and the second part 1042 include three relays 202. The three relays 202 in the first part 1041 are connected to phase a, phase b, and phase c of the inverter circuit 102, respectively, and the three relays 202 in the second part 1042 are connected to phase a, phase b, and phase c of the power grid 200, respectively.

[0078] For ease of description, the three relays 202 in the first part 1041 are labeled as relays KM1, KM2, and KM3, respectively, and the three relays 202 in the second part 1042 are labeled as relays KS1, KS2, and KS3, respectively. The inverter circuit 102's a-phase, relays KM1 and KS1, and the grid 200's a-phase are connected sequentially; the inverter circuit 102's b-phase, relays KM2 and KS2, and the grid 200's b-phase are connected sequentially; and the inverter circuit 102's c-phase, relays KM3 and KS3, and the grid 200's c-phase are connected sequentially.

[0079] As an example, relays KM1 and KM2 are controlled by control signal 1, relay KM3 is controlled by control signal 2, relay KS1 is controlled by control signal 3, and relays KS2 and KS3 are controlled by control signal 4. The relays 202 of the first part 1041 and the second part 1042 are divided into two groups by the control signals for redundant control.

[0080] As an example, relays KM1 and KM2 can be controlled by one control signal 1, or relays KM1 and KM2 can be controlled by two control signals 1 respectively; for control signal 4 to control relays KS2 and KS, the control of relays KM1 and KM2 by control signal 1 can be referred to.

[0081] Figure 2 This is a flowchart illustrating the voltage control method in an embodiment of this application. Figure 2 The voltage control methods include S102-S106.

[0082] S102: When multiple relays are in the detection state, obtain the wiring method between the inverter and the power grid.

[0083] As an example, multiple relays 202 being in a detection state can be understood as multiple relays 202 in the switching circuit 104 being in a self-testing open state. At this time, the inverter circuit 102 and the power grid 200 are disconnected. The wiring method between the inverter and the power grid can be understood as the wiring method between the inverter and the power grid, including three-wire and four-wire systems.

[0084] As an example, in a three-wire system, the inverter's a-phase line, b-phase line, and c-phase line are connected to the grid's a-phase line, b-phase line, and c-phase line, respectively. Specifically, the inverter's a-phase line is connected to the grid's a-phase line, the inverter's b-phase line is connected to the grid's b-phase line, and the inverter's c-phase line is connected to the grid's c-phase line.

[0085] As an example, in a four-wire system, the inverter's a-phase line, b-phase line, c-phase line, and neutral line n are connected to the grid's a-phase line, b-phase line, c-phase line, and neutral point n, respectively. Specifically, the inverter's a-phase line is connected to the grid's a-phase line, the inverter's b-phase line is connected to the grid's b-phase line, the inverter's c-phase line is connected to the grid's c-phase line, and the inverter's neutral line n is connected to the grid's neutral point n.

[0086] S104, determine the current control strategy for the inverter circuit based on the wiring method and the current three-phase grid voltage.

[0087] As an example, the voltage control method prior to step S104 also includes: obtaining the current three-phase grid voltage of the grid 200. Among them, the three-phase power grid voltage The voltage is a three-phase voltage, including the grid voltage of phase a. Phase b grid voltage and the grid voltage of phase C For example, the current three-phase grid voltage of grid 200 is collected. .

[0088] It is understandable that the current three-phase grid voltage of grid 200 is... , where is the current voltage of grid 200. The voltage of grid 200 is an AC voltage, which changes over time. Therefore, the current three-phase grid voltage of grid 200 is... It changes with the current moment.

[0089] As an example, depending on the wiring method and the three-phase power grid voltage... The current control strategy is determined in the three-phase coupled control mode and the three-phase independent control mode. The current control strategy is used to control the inverter circuit 102 in the inverter 100.

[0090] S106 controls the inverter circuit to output a three-phase drive voltage based on the current control strategy and the three-phase grid voltage, which serves as the three-phase inverter voltage for the inverter.

[0091] Based on the current control strategy and the three-phase grid voltage of grid 200, the inverter circuit 102 is controlled to output a three-phase drive voltage, which is then used as the three-phase inverter voltage of inverter 100. Among them, the three-phase inverter voltage It changes over time and is alternating current.

[0092] As an example, the three-phase inverter voltage of the inverter It can be the voltage at one end of the switch circuit 104 connected to the inverter circuit 102.

[0093] The first state of relay 202 includes a normal operating state and a fault state, and the first state of relay 202 is based on the three-phase power grid voltage. and three-phase inverter voltage Sure.

[0094] Under normal operating conditions, relay 202 can be controlled to be in the ON state by the control signal corresponding to the ON state, and can be controlled to be in the OFF state by the control signal corresponding to the OFF state. Under fault conditions, relay 202 cannot be controlled to be in the ON state by the control signal corresponding to the ON state, and / or cannot be controlled to be in the OFF state by the control signal corresponding to the OFF state.

[0095] In the above voltage control method, the voltage is controlled according to the wiring configuration between the inverter 100 and the power grid 200, and the current three-phase grid voltage of the power grid 200. In both three-phase coupled control and three-phase independent control modes, the current control strategy for controlling inverter circuit 102 is determined, based on the current control strategy and the three-phase grid voltage. The output of the control inverter circuit 102 is used as the three-phase inverter voltage. Three-phase drive voltage, avoiding three-phase inverter voltage and three-phase grid voltage If the voltage difference between the two sides is too large, the instantaneous inrush current of the relay 202 in the switching circuit 104 will be too large, which will affect the life of the relay, reduce the voltage imbalance of the half bus, and improve the service life of the inverter.

[0096] Figure 3 This is a flowchart illustrating how the current control strategy for the inverter circuit is determined based on the wiring configuration and the current three-phase grid voltage in this embodiment of the application. See [link to relevant documentation]. Figure 3 In one embodiment, based on the wiring scheme and the current three-phase grid voltage of grid 200 Determine the current control strategy for the inverter circuit 102, including:

[0097] S1042, when the wiring method is four-wire, obtains the maximum unbalance of the three-phase grid voltage based on the current three-phase grid voltage.

[0098] As an example, in the case of a four-wire wiring system, based on the current three-phase grid voltage of grid 200... Obtain the three-phase grid voltage The maximum imbalance includes S202 and S204.

[0099] S202, based on the three-phase power grid voltage The grid voltage of each phase is used to obtain multiple first differences, which represent the voltage deviation between any two phases of the grid voltage.

[0100] As an example, a three-phase power grid voltage This corresponds to the three initial differences. For example, the three-phase grid voltage... The grid voltage of each phase is the grid voltage of phase a. Phase b grid voltage and the grid voltage of phase C .

[0101] According to the grid voltage and grid voltage The first difference is obtained. Among them, the first difference According to the grid voltage and grid voltage The first difference is obtained. Among them, the first difference According to the grid voltage and grid voltage The first difference is obtained. Among them, the first difference .

[0102] S204, determine the maximum unbalance of the three-phase grid voltage based on multiple first differences.

[0103] As an example, determining the maximum imbalance of the three-phase grid voltage based on the first difference includes: obtaining multiple ratios based on multiple first differences and a first preset voltage, and taking the maximum value among the absolute values ​​of the multiple ratios as the maximum imbalance.

[0104] As an example, the first preset voltage corresponding to the first difference is obtained by summing the voltages of the two phases of the grid voltage corresponding to the first difference; the ratio corresponding to the first difference is obtained by summing the first difference and the first preset voltage corresponding to the first difference.

[0105] For example, based on the first difference Corresponding grid voltage and grid voltage The first difference is obtained. The corresponding first preset voltage Among them, the first preset voltage Based on the first difference Corresponding grid voltage and grid voltage The first difference is obtained. The corresponding first preset voltage Among them, the first preset voltage Based on the first difference Corresponding grid voltage and grid voltage The first difference is obtained. The corresponding first preset voltage Among them, the first preset voltage .

[0106] As an example, based on the first difference and the first difference The corresponding first preset voltage The first difference is obtained. The corresponding ratio; based on the first difference and the first difference The corresponding first preset voltage The first difference is obtained. The corresponding ratio; based on the first difference and the first difference The corresponding first preset voltage The first difference is obtained. The corresponding ratio; using the formula The three-phase grid voltage is obtained. The maximum imbalance.

[0107] As an example, based on the grid voltage of each phase in the three-phase grid voltage V1, the first preset voltage V is obtained; where, .

[0108] As an example, based on the first difference The first difference is obtained by comparing it with the first preset voltage V. The corresponding ratio; based on the first difference The first difference is obtained by comparing it with the first preset voltage V. The corresponding ratio; based on the first difference The first difference is obtained by comparing it with the first preset voltage V. The corresponding ratio; using the formula The three-phase grid voltage is obtained. The maximum imbalance.

[0109] As an example, the first preset voltage can be a standard voltage. For example, the first preset voltage is 220V; based on the first difference and standard voltage The first difference is obtained. The corresponding ratio; based on the first difference and standard voltage The first difference is obtained. The corresponding ratio; based on the first difference and standard voltage The first difference is obtained. The corresponding ratio; as an example, the formula is used. The three-phase grid voltage is obtained. The maximum imbalance.

[0110] S1044, if the maximum imbalance is less than or equal to the first threshold, determine the current control strategy as a three-phase coupling control mode.

[0111] As an example, comparing three-phase grid voltages The maximum imbalance degree and the first threshold H1 are used to determine the current three-phase grid voltage when the maximum imbalance degree is less than or equal to the first threshold H1. The imbalance is relatively small, and the current control strategy is a three-phase coupling control method. Based on the three-phase coupling control method and the current three-phase grid voltage... The inverter circuit 102 outputs a three-phase drive voltage, which serves as the three-phase inverter voltage of the inverter 100. When the relay 202 in the switching circuit 104 is engaged, the inrush current is relatively small and will not exceed the hardware specifications, that is, it will not exceed the inrush current withstand capacity of the relay 202. Therefore, it will not affect the lifespan of the relay 202 and will increase the lifespan of the inverter 100.

[0112] The first threshold H1 can be the maximum value of the unbalance of the three-phase grid voltage without affecting the service life of the relay 202 in the inverter 100, and can be used to characterize the tolerance of the relay 202.

[0113] As an example, the first threshold H1 can also be the product of the maximum value of the unbalance degree corresponding to the three-phase grid voltage without affecting the service life of the relay 202 in the inverter 100 and a coefficient less than 1. By setting this, when selecting the first threshold H1, the aging condition of the relay 202 is taken into account, and the influence of aging on the surge current withstand capability of the relay 202 can be eliminated, further improving the service life of the relay 202. For example, the coefficient less than 1 can be a value greater than or equal to 0.7 and less than or equal to 0.8.

[0114] In one embodiment, the current control strategy for controlling the inverter circuit 102 is determined based on the wiring method and the current three-phase grid voltage of the grid 200. The strategy further includes determining the current control strategy as a three-phase independent control mode when the maximum imbalance is greater than the first threshold H1.

[0115] As an example, comparing three-phase grid voltages The maximum imbalance degree and the first threshold H1 are used to determine the current three-phase grid voltage when the maximum imbalance degree is greater than the first threshold H1. The imbalance is significant, and the current control strategy is a three-phase independent control method. Based on the three-phase independent control method and the current three-phase grid voltage... The inverter circuit 102 outputs a three-phase drive voltage, which serves as the three-phase inverter voltage of the inverter 100. When the relay 202 in the switching circuit 104 is engaged, the inrush current is relatively small and will not exceed the hardware specifications, that is, it will not exceed the inrush current withstand capacity of the relay 202. Therefore, it will not affect the lifespan of the relay 202 and will increase the lifespan of the inverter 100.

[0116] In one embodiment, the voltage control method further includes: when the wiring system is a three-wire system, determining that the current control strategy is a three-phase coupling control mode.

[0117] In one embodiment, based on the current control strategy and the three-phase grid voltage... The inverter circuit 102 is controlled to output a three-phase drive voltage, including: when the current control strategy is a three-phase coupling control mode, based on the three-phase grid voltage... and preset d-axis voltage The first three-phase pulse modulation signal PWM1 is obtained to control the inverter circuit 102 to output the three-phase drive voltage.

[0118] Figure 4 This is one of the control block diagrams in this application for obtaining the first three-phase pulse modulation signal based on the three-phase grid voltage and the preset shaft voltage. See [link to relevant documentation]. Figure 4In one embodiment, a first three-phase pulse modulation signal is obtained based on the three-phase grid voltage and a preset d-axis voltage, including steps S301-S303.

[0119] S301, based on the three-phase grid voltage, obtain the q-axis voltage and rotation angle of the dq coordinate system.

[0120] As an example, the current three-phase grid voltage of grid 200 is collected. For three-phase power grid voltage Perform Clark transform and orthogonal Park transform to obtain the q-axis voltage in the dq coordinate system. and d-axis voltage According to the q-axis voltage The rotation angle used for the orthogonal Park transformation is obtained. This achieves phase-locking, enabling the first three-phase pulse modulation signal to control the three-phase drive voltage output by the inverter circuit 102. and three-phase grid voltage They are in the same phase.

[0121] It is understandable that, under accurate phase-locked loop (PLL) conditions, the q-axis voltage... Equal to 0, d-axis voltage It equals the amplitude of the three-phase grid voltage V1. This can be understood as the voltage on the q-axis. Non-zero, and q-axis voltage If it can be ignored, the q-axis voltage is considered to be negligible. It equals 0.

[0122] As an example, the phase-locked loop (PLL) is based on the q-axis voltage. The rotation angle used for the orthogonal Park transformation is obtained. .

[0123] As an example, regarding the voltage of a three-phase power grid Perform Clark transform and orthogonal Park transform to obtain the q-axis voltage in the dq coordinate system. and d-axis voltage This includes: the voltage of the three-phase power grid Perform a Clark transform to obtain the first α-axis voltage in the αβ coordinate system. and the first β-axis voltage For the first α-axis voltage and the first β-axis voltage Perform bandpass filtering; for the first α-axis voltage after bandpass filtering... and the first β-axis voltage Perform a forward-order Park transformation to obtain the q-axis voltage in the dq coordinate system. and d-axis voltage .

[0124] By applying the first α-axis voltage and the first β-axis voltage Bandpass filtering can filter out the first α-axis voltage. and the first β-axis voltage In the process, interference outside the fundamental frequency of the power grid is used to improve the obtained q-axis voltage. and d-axis voltage The accuracy.

[0125] As an example, a bandpass filter is used for the first α-axis voltage. and the first β-axis voltage Perform filtering.

[0126] S303, based on the q-axis voltage, rotation angle and preset d-axis voltage, obtains the first three-phase pulse modulation signal.

[0127] As an example, based on rotation angle For q-axis voltage and preset d-axis voltage Perform an inverse Park transformation to obtain the second α-axis voltage in the αβ coordinate system. Second β axis voltage According to the second α-axis voltage Second β axis voltage The first three-phase pulse modulation signal PWM1 is obtained; wherein, the first three-phase pulse modulation signal PWM1 includes the first pulse modulation signal PWM1a of phase a, the first pulse modulation signal PWM1b of phase b and the first pulse modulation signal PWM1c of phase c.

[0128] As an example, based on rotation angle For q-axis voltage and preset d-axis voltage Perform inverse Park transformation, including: for q-axis voltage Perform low-pass filtering; based on rotation angle The q-axis voltage after low-pass filtering and preset d-axis voltage Perform an inverse-order Park transformation. This is done by adjusting the q-axis voltage. Low-pass filtering can stabilize the q-axis voltage. To avoid q-axis voltage Phase-locked loop malfunction, q-axis voltage Excessive fluctuations affect the preset d-axis voltage. .

[0129] As an example, a low-pass filter is used for the q-axis voltage. Perform low-pass filtering.

[0130] As an example, the voltage control method also includes: obtaining a preset d-axis voltage. .

[0131] As an example, to obtain the preset d-axis voltage ,include:

[0132] Obtain the initial preset d-axis voltage Based on rotation angle For q-axis voltage and the initial preset d-axis voltage Perform an inverse Park transformation to obtain the second initial α-axis voltage in the αβ coordinate system. Second initial β-axis voltage The root mean square (RMS) limiting method is used, based on the second initial α-axis voltage. Second initial β-axis voltage The root mean square (RMS) value is obtained; the initial preset d-axis voltage is adjusted according to the different RMS and RMS threshold values ​​A. And the adjusted initial preset d-axis voltage Repeat the step of obtaining the root mean square value (RMS) until the RMS value and the RMS threshold A are the same; where the RMS threshold A represents the conversion efficiency of the inverter 100.

[0133] The preset d-axis voltage is obtained by means of root mean square limiting. This can avoid the problem that the three-phase drive voltage output by the inverter circuit 102 controlled by the first three-phase pulse modulation signal PWM1 is less than the theoretical value.

[0134] As an example, the formula is used. The root mean square (RMS) value is obtained.

[0135] As an example, using the SVPWM modulation algorithm, based on the second α-axis voltage... Second β axis voltage The first three-phase pulse modulation signal PWM1 is obtained; using the formula The root mean square threshold A is obtained; where, This refers to the DC bus voltage received by inverter 100. As an example, The inverter 100 converts the DC bus voltage The conversion efficiency of converting to three-phase AC voltage.

[0136] As an example, the initial preset d-axis voltage is adjusted based on different root mean square (RMS) values ​​and RMS threshold values ​​A. And the adjusted initial preset d-axis voltage Repeat the steps to obtain the root mean square value (RMS) until the RMS value and the RMS threshold A are the same, including steps S302-S304.

[0137] S302, when the root mean square value (RMS) is less than the root mean square threshold (A), increase the initial preset d-axis voltage. And the initial preset d-axis voltage after the increase Repeat the steps to obtain the root mean square (RMS) value.

[0138] S304, when the root mean square value (RMS) is greater than the root mean square threshold (A), the initial preset d-axis voltage is reduced proportionally. and q-axis voltage And the reduced initial preset d-axis voltage and q-axis voltage Repeat the steps to obtain the root mean square (RMS) value until the RMS value and the RMS threshold A are the same.

[0139] By proportionally reducing the initial preset d-axis voltage and q-axis voltage This can avoid the q-axis voltage from being affected by phase-locked loop anomalies. The effect of fluctuations on the first three-phase pulse modulation signal PWM1.

[0140] As an example, the modulation controller is based on the second α-axis voltage. Second β axis voltage Output the first three-phase pulse modulation signal PWM1.

[0141] Figure 5 This is the second control block diagram in this application embodiment for obtaining the first three-phase pulse modulation signal based on the three-phase grid voltage and the preset shaft voltage. See [link to relevant documentation]. Figure 5 In one embodiment, based on the current control strategy and the three-phase grid voltage The inverter circuit 102 is controlled to output three-phase drive voltage, including: when the current control strategy is three-phase independent control mode, according to the three-phase grid voltage... The grid voltage of each phase and the first modulation ratio coefficient K1 are used to obtain the first three-phase pulse modulation signal corresponding to the grid voltage of each phase, so as to control the inverter circuit 102 to output the three-phase drive voltage.

[0142] As an example, in the case where the current control strategy is a three-phase independent control mode, the voltage control method also includes: based on the three-phase grid voltage Determine the phase sequence of the grid voltage for each phase, determine whether phase b and phase c are reversed, and achieve phase locking.

[0143] As an example, three-phase grid voltage The voltage is a three-phase voltage, including the grid voltage of phase a. Phase b grid voltage and the grid voltage of phase C Under the current control strategy of three-phase independent control, based on the grid voltage of phase a... The first pulse modulation signal PWM1a for phase a is obtained by combining the first modulation ratio coefficient K1; based on the grid voltage of phase b... The first pulse modulation signal PWM1b for phase b is obtained by combining the first modulation ratio coefficient K1; based on the grid voltage of phase c... The first pulse modulation signal PWM1c of phase c is obtained by combining the first modulation ratio coefficient K1; wherein, the first three-phase pulse modulation signal PWM1 includes the first pulse modulation signal PWM1a of phase a, the first pulse modulation signal PWM1b of phase b and the first pulse modulation signal PWM1c of phase c.

[0144] like Figure 5 As shown, the first modulator is configured with a first modulation ratio coefficient K1, and the first modulator adjusts according to the grid voltage. The first pulse modulation signal PWM1a is obtained by combining the first modulation ratio coefficient K1; based on the grid voltage... The first pulse modulation signal PWM1b is obtained by combining the first modulation ratio coefficient K1; based on the grid voltage... The first pulse modulation signal PWM1c is obtained by combining the first modulation ratio coefficient K1 with the first modulation factor K1. As an example, the first modulator is used to modulate the grid voltage... Grid voltage and grid voltage Data normalization is performed to obtain the first pulse modulation signal corresponding to each phase of the power grid voltage. As an example, the first modulation ratio coefficient K1 = .

[0145] See Figure 5 In one embodiment, based on the current control strategy and the three-phase grid voltage The inverter circuit 102 is controlled to output three-phase drive voltage, including: when the current control strategy is three-phase independent control mode, according to the three-phase grid voltage... The grid voltage of each phase and the first modulation ratio coefficient K1 are used to obtain the first three-phase pulse modulation initial signal corresponding to the grid voltage of each phase; the first three-phase pulse modulation initial signal corresponding to the grid voltage of each phase is subjected to amplitude limiting processing to obtain the first three-phase pulse modulation signal corresponding to the grid voltage of each phase.

[0146] By using amplitude limiting, the first three-phase pulse modulation signals corresponding to the grid voltage of each phase maintain a good output waveform. As an example, the amplitude limiting process is a gradual start-up process, increasing from 0 to 1.

[0147] As an example, a first limiting module is used to limit the initial three-phase pulse modulation signal corresponding to the grid voltage of each phase, and output the first three-phase pulse modulation signal corresponding to the grid voltage of each phase. As an example, a maximum duty cycle of 0.3 is used to limit the initial three-phase pulse modulation signal corresponding to the grid voltage of each phase, and output the first three-phase pulse modulation signal corresponding to the grid voltage of each phase.

[0148] In one embodiment, controlling the inverter circuit to output a three-phase drive voltage based on the current control strategy and the three-phase grid voltage includes: controlling the inverter circuit to output a three-phase drive voltage based on the current control strategy and the three-phase grid voltage. The current three-phase inverter current of inverter circuit 102 The inverter current of each phase and the second modulation ratio coefficient control the output of the three-phase drive voltage of the inverter circuit 102.

[0149] The inverter current of each phase in the current three-phase inverter current of the inverter circuit 102 and the second modulation ratio coefficient are used to control the output three-phase drive voltage of the inverter circuit 102 to achieve current loop compensation and avoid damage to the relay 202 by excessive inrush current.

[0150] As an example, three-phase inverter current The inverter current of each phase can be considered as the inverter current of phase a. The inverter current of phase b and the inverter current of phase c Three-phase drive voltage It can be the driving voltage of phase a The driving voltage of phase b and the driving voltage of phase c .

[0151] Figure 6 This is a schematic diagram of the process for controlling the output three-phase drive voltage of the inverter circuit in an embodiment of this application. See also... Figure 6 In one embodiment, based on the current control strategy and the three-phase grid voltage The current three-phase inverter current of inverter circuit 102 The inverter current of each phase and the second modulation ratio K2 control the output three-phase drive voltage of the inverter circuit 102. Including: S402-S406.

[0152] S402, based on the current control strategy and the three-phase grid voltage, obtain the first three-phase pulse modulation signal PWM1 corresponding to the three-phase grid voltage.

[0153] It is understood that the specific steps for obtaining the first three-phase pulse modulation signal PWM1 corresponding to the three-phase grid voltage based on the current control strategy and the three-phase grid voltage can be referred to the corresponding description in the above embodiments, and will not be repeated here.

[0154] S404 obtains the second three-phase pulse modulation signal based on the inverter current of each phase and the second modulation ratio coefficient.

[0155] As an example, based on the target inverter current I and the inverter current of phase a... The second pulse modulation signal PWM2a for phase a is obtained from the second modulation ratio coefficient K2; based on the target inverter current I and the inverter current of phase b... The second pulse modulation signal PWM2b for phase b is obtained from the second modulation ratio coefficient K2; based on the target inverter current and the inverter current of phases I and c... The second modulation ratio coefficient K2 is used to obtain the second pulse modulation signal PWM2c for phase c; wherein, the second pulse modulation signal PWM2c includes the second pulse modulation signal PWM2a for phase a, the second pulse modulation signal PWM2b for phase b, and the second pulse modulation signal PWM2c for phase c. As an example, the target inverter current I is 0.

[0156] As an example, the second modulation ratio coefficient K2 is the same as the first modulation ratio coefficient K1.

[0157] Figure 7 This is a control block diagram for obtaining the second three-phase pulse modulation signal based on the inverter current of each phase and the second modulation ratio coefficient in an embodiment of this application. See [link to relevant documentation]. Figure 7 The PI controller is based on the target inverter current I and the inverter current. The difference is used to output the phase a voltage, based on the target inverter current I and the inverter current. The difference is used to output the b-phase voltage, based on the target inverter current I and the inverter current. The difference is used to output the c-phase voltage; the second modulator is connected to the PI controller and is configured with a second modulation ratio coefficient K2; it is used to output the second pulse modulation signal PWM2a according to the a-phase voltage and the second modulation ratio coefficient K2, output the second pulse modulation signal PWM2b according to the b-phase voltage and the second modulation ratio coefficient K2, and output the second pulse modulation signal PWM2c according to the c-phase voltage and the second modulation ratio coefficient K2.

[0158] S406 controls the inverter circuit to output three-phase drive voltage based on the first three-phase pulse modulation signal and the second three-phase pulse modulation signal.

[0159] As an example, a three-phase pulse control signal PWM is obtained based on the first three-phase pulse modulation signal PWM1 and the second three-phase pulse modulation signal PWM2; wherein, the three-phase pulse control signal PWM controls the inverter circuit 102 to output a three-phase drive voltage. .

[0160] For example, the three-phase pulse control signal PWM includes a pulse modulation signal PWMa for phase a, a pulse modulation signal PWMb for phase b, and a pulse modulation signal PWMc for phase c; wherein, the pulse modulation signal PWMa controls the inverter circuit 102 to output the drive voltage of phase a. The pulse modulation signal PWMb controls the drive voltage of phase b of the inverter circuit 102. The pulse modulation signal PWMc controls the drive voltage of phase c of the inverter circuit 102. .

[0161] As an example, the pulse modulation signal PWMa for phase a is obtained based on the first pulse modulation signal PWM1a and the second pulse modulation signal PWM2a; the pulse modulation signal PWMb for phase b is obtained based on the first pulse modulation signal PWM1b and the second pulse modulation signal PWM2b; and the pulse modulation signal PWMc for phase c is obtained based on the first pulse modulation signal PWM1c and the second pulse modulation signal PWM2c.

[0162] For example, the first pulse modulation signal and the second pulse modulation signal of each phase are summed to obtain the pulse modulation signal of each phase; wherein, , , .

[0163] As an example, the second modulator can be the first modulator connected to the PI controller; the first modulator adjusts according to the mains voltage. The superposition of the phase a voltage and the first modulation ratio coefficient K1 generates the pulse modulation signal PWMa for phase a; based on the grid voltage... The superposition of the phase b voltage and the first modulation ratio coefficient K1 generates the phase b pulse modulation signal PWMb; based on the grid voltage... The superposition of the phase c voltage and the first modulation ratio coefficient K1 generate the phase c pulse modulation signal PWMc.

[0164] As an example, before outputting the pulse modulation signal, the voltage control method further includes a step of limiting the pulse modulation signal.

[0165] It should be understood that, although Figure 2 , Figure 3 and Figure 6The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 2 , Figure 3 and Figure 6 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0166] Based on the same inventive concept, this application also provides a detection method. The solution provided by the detection method is similar to the solution described in the voltage control method above. The parts that are the same as or corresponding to the embodiments in the voltage control method above will not be described in detail below.

[0167] Figure 8 This is one of the flowcharts illustrating the detection method in this embodiment of the disclosure. See also: Figure 1 and Figure 8 In this embodiment, a detection method is provided, which is applied to an inverter 100. The inverter 100 includes an inverter circuit 102 and a switching circuit 104. The switching circuit 104 includes a plurality of relays 202 that are respectively connected to the inverter circuit 102 and the power grid 200. The detection method includes steps S502-S506.

[0168] S502, when multiple relays are in the open state, controls the inverter circuit to output a three-phase drive voltage according to the voltage control method described above, which serves as the three-phase inverter voltage of the inverter.

[0169] Having multiple relays 202 in the open state can mean that the relays 202 are disconnected, and the inverter circuit 102 and the power grid 200 are disconnected. When multiple relays are in the open state, according to the voltage control method described above, the inverter circuit 102 in the inverter 100 is controlled to output a three-phase drive voltage, which serves as the three-phase inverter voltage of the inverter 100.

[0170] S504, when multiple relays are in the on state and the inverter circuit stops working, obtains the three-phase output voltage at the output terminal of the inverter as the three-phase inverter voltage.

[0171] As an example, multiple relays 202 being in the ON state can mean that relays 202 are short-circuited, and the inverter circuit 102 and the power grid 200 are connected through relays 202; the inverter circuit 202 stopping operation can mean that the inverter circuit 202 stops outputting three-phase drive voltage. As an example, the output terminal of the inverter 100 can be the end where the inverter 100 and the power grid 200 are connected.

[0172] As an example, when multiple relays 202 are in the ON state and the inverter circuit 102 in the inverter 100 is not working, the inverter circuit 102 and the power grid 200 are connected through relays 202 to collect the three-phase output voltage at the output terminal of the inverter 100 as the three-phase inverter voltage. .

[0173] S506 determines the first state of the relay based on the three-phase inverter voltage and the three-phase grid voltage.

[0174] As an example, obtain the current three-phase grid voltage of grid 200. Based on the condition that multiple relays are in the open state, the three-phase inverter voltage at the same time and three-phase grid voltage And, based on the condition that multiple relays are in the on state, the three-phase inverter voltage at the same time and three-phase grid voltage This is used to determine the first state of the multiple relays 202 in the switching circuit 104; wherein the first state includes normal operation state and fault state.

[0175] As an example, when multiple relays are in the off state, the three-phase inverter voltage at the same time... and three-phase grid voltage The multiple relays 202 in the switching circuit 104 are determined to be the first target state in the first state; when multiple relays are in the conducting state, the three-phase inverter voltage at the same time is used to determine the first target state. and three-phase grid voltage The system determines that multiple relays 202 in the switching circuit 104 are in the second target state within the first state; if both the first target state and the second target state are normal operating states, the multiple relays 202 are determined to be in the normal operating state. If either the first target state or the second target state is a fault state, the multiple relays 202 are determined to be in the fault state.

[0176] In the above detection method, when multiple relays 202 are in the open state, the detection method is determined based on the wiring configuration between the inverter 100 and the power grid 200, and the current three-phase voltage of the power grid 200. Determine the current control strategy for the inverter circuit 102 in both three-phase coupled control and three-phase independent control modes; based on the current control strategy and the three-phase grid voltage... The output of the control inverter circuit 102 is used as the three-phase inverter voltage. The three-phase drive voltage. To avoid the three-phase inverter voltage during the detection of relay 202. and three-phase grid voltage If the voltage difference between the relays is too large, the inrush current will be too high when the relay 202 in the switching circuit 104 is activated, affecting the lifespan of the relay 202. Reducing the half-bus voltage imbalance will improve the lifespan of the inverter 100. When multiple relays 202 are in the conducting state and the inverter circuit 202 is not working, the three-phase output voltage at the output terminal of the inverter 202 is obtained as the three-phase inverter voltage. According to the three-phase inverter voltage and three-phase grid voltage This allows the first state of relay 202 to be determined, enabling the detection of relay 202 in inverter 100.

[0177] As an example, the detection method also includes: when the first state of relay 202 is a fault condition, sending a fault signal to stop the detection of relay 202; wherein, the fault signal indicates that relay 202 is faulty and inverter 100 cannot work normally.

[0178] In some embodiments, the detection method further includes the step of detecting the adhesion of multiple relays 202 in the switching circuit 104.

[0179] As an example, multiple relays 202 in the control switching circuit 104 are turned on or off; based on the three-phase inverter voltage of the inverter 100. The three-phase grid voltage of the power grid is 100. Determine whether relay 202 has an adhesion abnormality.

[0180] As an example, before the multiple relays 202 in the control switch circuit 104 are turned on or off, the detection method also includes: controlling the inverter circuit 102 to be in a stopped working state.

[0181] Figure 9 This is a flowchart illustrating the process of determining the first state of the relay based on the three-phase inverter voltage and the three-phase grid voltage in an embodiment of this application. See [link to relevant documentation]. Figure 9 In one embodiment, based on the three-phase inverter voltage and three-phase grid voltage The first state of relay 202 is determined, including steps S5062-S5066.

[0182] S5062, based on the three-phase drive voltage output by the inverter circuit and the three-phase grid voltage, obtains the first voltage difference.

[0183] As an example, the three-phase drive voltage output by inverter circuit 102 at time T1 is obtained as the three-phase inverter voltage at time T1 (current). And obtain the three-phase grid voltage of grid 200 at time T1. Based on the three-phase grid voltage at time T1 and three-phase inverter voltage The first pressure difference at time T1 is obtained. ;in, , Three-phase power grid voltage The effective value, Three-phase inverter voltage Valid value.

[0184] It can be understood that time T1 can be any time during the process when multiple relays 202 in the switching circuit 104 are in the open state and the inverter circuit 102 outputs three-phase drive voltage.

[0185] S5064, when the inverter stops working, obtains the second voltage difference based on the three-phase inverter voltage and the three-phase grid voltage.

[0186] As an example, when multiple relays are in the ON state and inverter 100 is not working, the three-phase output voltage at the output terminal of inverter 100 at time T2 is obtained as the current three-phase inverter voltage of inverter 100. And obtain the three-phase grid voltage of grid 200 at time T2. Based on the three-phase grid voltage at time T2 and three-phase inverter voltage The second pressure difference at time T2 is obtained. ;in, , Three-phase power grid voltage The effective value, Three-phase inverter voltage Valid value.

[0187] It can be understood that time T2 can be any time during the process when multiple relays in the switching circuit 104 are in the on state and the inverter 100 stops working.

[0188] S5066: If the first voltage difference is less than the first voltage threshold and the second voltage difference is less than the second voltage threshold, the relay is determined to be in normal working condition.

[0189] As an example, the first pressure difference can be compared separately. And the first voltage threshold A1, and compare the second voltage difference. Second voltage threshold A2; in the first voltage difference Less than the first voltage threshold A1, and the second voltage difference If the voltage is less than the second voltage threshold A1, it is determined that the relay 202 is in normal working condition.

[0190] As an example, the first pressure difference can be obtained separately. The difference between the first voltage threshold A1 and the second voltage difference The difference between the second voltage threshold A2 and the second voltage threshold A2; if both differences are less than 0, it is determined that the relay 202 is in normal working condition.

[0191] As an example, the first voltage threshold A1 can be the difference between the effective value of the three-phase drive voltage (which is the three-phase inverter voltage) and the effective value of the three-phase grid voltage at the same moment, when multiple relays 202 in the switching circuit are all in the on state and the inverter circuit 102 outputs a three-phase drive voltage. As an example, relay 202 being in the on state can mean that relay 202 is in the energized state.

[0192] As an example, the second voltage threshold A2 can be the difference between the effective value of the three-phase output voltage (which is the three-phase inverter voltage) and the effective value of the three-phase grid voltage at the same moment when multiple relays 202 in the switching circuit are all in the on state and the inverter circuit 102 stops working.

[0193] Figure 10 This is the second flowchart illustrating the detection method in this application embodiment. See also... Figure 1 and 9 The detection method includes steps S602-S610.

[0194] S602, check the adhesion of all relays.

[0195] Figure 11 Examples of embodiments in this application Figure 10 See the flowchart of S602. Figure 11 The system controls the disconnection of multiple relays 202, and after a certain period of time, the delay time is satisfied. Theoretically, at this time, relays KM1, KM2, KM3, KS1, KS2, and KS3 are all in the disconnected state. The system then acquires the current three-phase output voltage of the inverter 100 as the three-phase inverter voltage. And obtain the current three-phase grid voltage of grid 200. According to the three-phase power grid voltage and three-phase inverter voltage The third pressure difference is obtained. ,in, , Three-phase power grid voltage The effective value, Three-phase inverter voltage The effective value. As an example, the first time is greater than the mechanical action delay of relay 202, and the three-phase grid voltage is detected after the first time. and three-phase inverter voltage This ensures that the multiple relays 202 in the switching circuit 104 meet the control requirements.

[0196] In the third pressure difference If the voltage is less than the third voltage threshold A3, it is determined that among the multiple relays 202 located between the three phases of the inverter circuit 102 and the three phases of the power grid 200, at least one corresponding relay 202 is stuck, and the first state of the relay 202 is a fault state.

[0197] As an example, the third voltage threshold A3 can be the third differential voltage when all relays 202 in the switching circuit 104 are in the open state. The theoretical value. For example, the third voltage threshold A3 is... For example, 50V.

[0198] As an example, at least one corresponding relay 202 is stuck, which can be one corresponding relay 202 from phase a, phase b, and phase c. For example, if the relay 202 corresponding to phase a is stuck, then at least one of relays KM1 and KS1 is stuck; if the relay 202 corresponding to phase b is stuck, then at least one of relays KM2 and KS2 is stuck; if the relay 202 corresponding to phase c is stuck, then at least one of relays KM3 and KS3 is stuck.

[0199] As an example, at least one corresponding relay 202 is stuck together, which can be any two corresponding relays 202 in phases a, b, and c. For example, if the relays 202 corresponding to phases a and b are stuck together, then at least one of relays KM1 and KS1 is stuck together, and at least one of relays KM2 and KS2 is stuck together.

[0200] As an example, the relay 202 corresponding to phase b and phase c is stuck together, and the relay 202 corresponding to phase c and phase a is stuck together. For the same situation, please refer to the description of the relay 202 corresponding to phase a and phase b stuck together above, which will not be repeated here.

[0201] As an example, at least one corresponding relay 202 is stuck together, which could mean that relays 202 corresponding to phases a, b, and c are all stuck together. In this case, at least one of relays KM1 and KS1 is stuck together, at least one of relays KM2 and KS2 is stuck together, and at least one of relays KM3 and KS3 is stuck together.

[0202] S604, detects the adhesion of relays KS1 and KM3.

[0203] Figure 12 Examples of embodiments in this application Figure 10 See the flowchart of S604. Figure 12 As an example, after step S602, relays KM1, KM2, KS2, and KS3 in multiple relays 202 are turned on and remain on for a first time, which satisfies the delay time. Theoretically, at this time, relays KM1, KM2, KS2, and KS3 are all in the on state, while relays KM3 and KS1 are all in the off state. The current three-phase output voltage of the inverter 100 is obtained as the three-phase inverter voltage. And obtain the current three-phase grid voltage of grid 200. According to the three-phase power grid voltage and three-phase inverter voltage The fourth pressure difference is obtained. ,in, , Three-phase power grid voltage The effective value, Three-phase inverter voltage Valid value.

[0204] In the fourth pressure difference If the voltage is less than the third voltage threshold A3, it is determined that at least one of relays KM3 and KS1 is stuck together, and the first state of relay 202 is a fault state.

[0205] It is understandable that in the fourth pressure difference If the voltage is less than the third voltage threshold A3, it is determined that a loop is formed between the inverter circuit 102 and the power grid 200, that is, there is a two-phase connection between the inverter circuit 102 and the power grid 200.

[0206] As an example, in the fourth pressure differential If the voltage exceeds the third voltage threshold A3, it is determined that relays KS1 and KM3 are not stuck together.

[0207] S606, Check the adhesion of relays KS2 and KS3.

[0208] Figure 13 Examples of embodiments in this application Figure 10 See the flowchart of S606. Figure 13 As an example, after step S602 or step S604, relays KM1, KM2, KM3, and KS1 in multiple relays 202 are controlled to be turned on, and after a first time, the delay time is satisfied. Theoretically, at this time, relays KM1, KM2, KM3, and KS1 are all in the on state, and relays KS2 and KS3 are all in the off state. The current three-phase output voltage of the inverter 100 is obtained as the three-phase inverter voltage. And obtain the current three-phase grid voltage of grid 200. According to the three-phase power grid voltage and three-phase inverter voltage The fifth pressure difference is obtained. ,in, , Three-phase power grid voltage The effective value, Three-phase inverter voltage Valid value.

[0209] In the fifth pressure difference If the voltage is less than the third voltage threshold A3, it is determined that at least one of relays KS2 and KS3 is stuck together, and the first state of relay 202 is a fault state.

[0210] As an example, in the fifth pressure differential If the voltage exceeds the third voltage threshold A3, it is determined that relays KS2 and KS3 are not stuck together.

[0211] S608, check the adhesion of relays KM1 and KM2.

[0212] Figure 14 Examples of embodiments in this application Figure 10 See the flowchart of S608. Figure 14 As an example, after step S602 or step S606, relays KM3, KS1, KS2, and KS3 in multiple relays 202 are controlled to be turned on, and after a first time, the delay time is satisfied. Theoretically, at this time, relays KM3, KS1, KS2, and KS3 are all in the on state, and relays KM1 and KM2 are all in the off state. The current three-phase output voltage of the inverter 100 is obtained as the three-phase inverter voltage. And obtain the current three-phase grid voltage of grid 200. According to the three-phase power grid voltage and three-phase inverter voltage The sixth pressure difference is obtained. ,in, , Three-phase power grid voltage The effective value, Three-phase inverter voltage Valid value.

[0213] At the sixth pressure difference If the voltage is less than the third voltage threshold A3, it is determined that at least one of relays KM1 and KM2 is stuck together, and the first state of relay 202 is a fault state.

[0214] As an example, in the sixth pressure differential If the voltage exceeds the third voltage threshold A3, it is determined that relays KM1 and KM2 are not stuck together.

[0215] S610, check all relays for open circuits.

[0216] Figure 15 Examples of embodiments in this application Figure 10 See the flowchart of S610. Figure 15 The control circuit disconnects all relays 202 in the switching circuit 104. According to the voltage control method described above, the inverter circuit 102 outputs a three-phase drive voltage, which serves as the three-phase inverter voltage for the inverter 100. This activates the relay drive, and the three-phase inverter voltage of the inverter 100 controls multiple relays 202 to momentarily engage, thus initiating waveform generation and acquiring the three-phase inverter voltage at time T1 (current). And obtain the three-phase grid voltage of grid 200 at time T1. Based on the three-phase grid voltage at time T1 and three-phase inverter voltage The first pressure difference at time T1 is obtained. .

[0217] First pressure difference If the voltage is less than the first voltage threshold A1, it is determined that the multiple relays 202 in the switching circuit 104 can be turned on by the control signal. After controlling all relays 202 in the switching circuit 104 to be turned on for a first time (i.e., after the delay time is met), theoretically, relays KM1, KM2, KM3, KS1, KS2, and KS3 are all in the on state. Then, the inverter circuit 102 is stopped, i.e., the drive of all relays 202 in the switching circuit 104 is turned off. After the first time (i.e., after the delay time is met), all relays 202 are in the on state, and the inverter circuit 102 stops working.

[0218] Obtain the three-phase output voltage at the output terminal of inverter 100 as the three-phase inverter voltage at time T2. And obtain the three-phase grid voltage of grid 200 at time T2. Based on the three-phase grid voltage at time T2 and three-phase inverter voltage The second pressure difference at time T2 is obtained. .

[0219] Second pressure difference If the voltage is less than the second voltage threshold A2, it is determined that the relay 202 is in normal working condition.

[0220] Second pressure difference If the voltage exceeds the second voltage threshold A2, it is determined that relay 202 is in a fault state. The driving of all relays 202 in the switching circuit 104 is turned off, and all relays 202 are controlled to open. This determines whether relay 202 can be normally controlled to be in the on and off states when it is open, thus obtaining the first state of relay 202.

[0221] As an example, during the execution of the detection method, the grid voltage is continuously present in the grid 200; before step S602, the control signals of multiple relays 202 in the switching circuit 104 are turned off until step S608 is completed, that is, the inverter circuit 102 in the control inverter 100 is in a stopped state; at this time, multiple relays 202 are disconnected, that is, relays KM1, KM2, KM3, KS1, KS2, and KS3 are all in the disconnected state. Steps S602-S608 are steps for detecting the adhesion of multiple relays 202 in the switching circuit 104.

[0222] In one embodiment, the detection method further includes: responding to the current three-phase inverter current of the inverter 100 when the inverter circuit 102 outputs a three-phase drive voltage. When the second state of multiple relays 202 meets the preset conditions, the multiple relays 202 are controlled to be in the open state, and the inverter circuit 102 is controlled to stop working; wherein, the second state includes the open state and the on state.

[0223] This setting allows the relay 202 to be disconnected during the detection of relay 102, and the inverter circuit 102 to stop working, further preventing excessive half-bus bias and inrush current from damaging the relay 202 and affecting its service life.

[0224] In one embodiment, in response to the current three-phase inverter current of inverter 1000 When the second state of multiple relays 202 meets the preset conditions, the multiple relays 202 are controlled to be in the open state, and the inverter circuit 202 is controlled to stop working, including steps S702-S704.

[0225] S702, in which each relay 202 is in the ON state, and the three-phase inverter current... The absolute value of the inverter current in each phase is greater than the first preset current. In this case, determine the three-phase inverter current. The second state of relay 202 satisfies the preset conditions.

[0226] S704, when relay 202 is in the open state and at least one of the absolute values ​​of the inverter current of each phase is a second threshold H2, determine the three-phase inverter current. The second state of relay 202 satisfies the preset conditions.

[0227] Figure 16 This is the third flowchart illustrating the detection method in this embodiment of the present disclosure. Figure 16 As an example, when the inverter circuit 102 outputs a three-phase drive voltage, it is determined that the drive is on. Then, the second states of multiple relays 202 in the switching circuit 104 are obtained. When all the second states of multiple relays 202 in the switching circuit 104 are in the on state, that is, when the second states of relays KM1, KM2, KM3, KS1, KS2, and KS3 are all in the on state, it is determined that all the relays 202 in the switching circuit 104 are engaged, and the current three-phase inverter current of the inverter 1000 is obtained. .

[0228] It is understandable that the three-phase inverter current... The inverter current of each phase can be the inverter current of phase a. The inverter current of phase b and the inverter current of phase c In inverter current absolute value, inverter current The absolute value and inverter current The absolute values ​​of all of them are greater than the first preset current. In this case, determine the three-phase inverter current. The absolute value of the inverter current in each phase is greater than the first preset current. Three-phase inverter current When the second state of relay 202 meets the preset conditions, multiple relays 202 in the control switch circuit 104 are in the open state, and the inverter circuit 102 is stopped working, that is, the drive to close the relay is turned off.

[0229] As an example, in inverter current absolute value, inverter current The absolute value and inverter current The absolute value of the current contains at least one value less than or equal to the first preset current. In this case, the test ends.

[0230] As an example, when the inverter circuit 102 outputs a three-phase drive voltage, and at least one of the multiple relays 202 in the switching circuit 104 is in an open state (i.e., at least one of relays KM1, KM2, KM3, KS1, KS2, and KS3 is in an open state), the current three-phase inverter current of the inverter 1000 is obtained. .

[0231] It is understandable that the three-phase inverter current... The inverter current of each phase can be the inverter current of phase a. The inverter current of phase b and the inverter current of phase c In inverter current absolute value, inverter current The absolute value and inverter current If at least one of the absolute values ​​of the inverter current is greater than or equal to the second threshold H2, then the three-phase inverter current is determined to be... When the second state of relay 202 meets the preset conditions, multiple relays 202 in the control switch circuit 104 are in the open state, and the inverter circuit 102 is stopped working, that is, the drive to close the relay is turned off.

[0232] As an example, the second threshold H2 can be a current value less than or equal to the rated current value of inverter 100. If the second threshold H2 is too small, the inverter circuit 102 will stop working prematurely, i.e., the drive will be shut down early, resulting in more half-bus imbalance. If the second threshold H2 is too large, it will affect the safety of inverter 100. In practical applications, an appropriate second threshold H2 can be selected based on the actual situation. It can be understood that when the drive is present, the inverter circuit 102 operates normally, and the three-phase inverter current... It will gradually rise until it reaches its maximum value and then stabilizes.

[0233] As an example, in inverter current absolute value, inverter current The absolute value and inverter current Among the absolute values, at least one is greater than or equal to the second threshold H2, which can be used as the inverter current. absolute value, inverter current The absolute value and inverter current Among the absolute values, there exists one that is greater than or equal to the second threshold H2; it can also be the inverter current. absolute value, inverter current The absolute value and inverter current Of the absolute values, any two are greater than or equal to the second threshold H2; it can also be the inverter current. absolute value, inverter current The absolute value and inverter current The absolute values ​​of all are greater than or equal to the second threshold H2.

[0234] In some embodiments, the detection method further includes: when the relay 202 is in the open state and the absolute value of the inverter current of each phase is less than the second threshold H2, obtaining a first preset current based on the maximum and minimum values ​​of the absolute values ​​of the inverter current of each phase. This setting allows us to obtain the first preset current corresponding to inverter 100. .

[0235] See Figure 16 As an example, when the inverter circuit 102 outputs a three-phase drive voltage, and at least one of the multiple relays 202 in the switching circuit 104 is in an open state (i.e., at least one of relays KM1, KM2, KM3, KS1, KS2, and KS3 is in an open state), the current three-phase inverter current of the inverter 1000 is obtained. .

[0236] It is understandable that the three-phase inverter current... The inverter current of each phase can be the inverter current of phase a. The inverter current of phase b and the inverter current of phase c In inverter current absolute value, inverter current The absolute value and inverter current When the absolute values ​​of all phases are less than the second threshold H2, obtain the maximum and minimum values ​​of the absolute values ​​of the inverter currents of each phase; and based on the maximum and minimum values ​​of the absolute values ​​of the inverter currents of each phase, obtain the first preset current. .

[0237] As an example, the first preset current is obtained based on the maximum and minimum absolute values ​​of the inverter currents of each phase. This includes: obtaining the average of the maximum and minimum absolute values ​​of the inverter current of each phase, and using the average value as the first preset current. .Right now Where X is the maximum absolute value of the inverter current of each phase, and Y is the minimum absolute value of the inverter current of each phase.

[0238] It should be understood that, although Figure 8 , Figure 9 , Figure 10 , Figure 11 , Figure 12 , Figure 13 , Figure 14 , Figure 15 and Figure 16 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 8 , Figure 9 , Figure 10 , Figure 11 , Figure 12 , Figure 13 , Figure 14 , Figure 15 and Figure 16 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0239] Based on the same inventive concept, this application also provides an inverter, the solution to the problem provided by the inverter is similar to the solution described in the above voltage control method or detection method, and the parts that are the same as or corresponding to the embodiments in the above voltage control method or detection method will not be described in detail below.

[0240] Figure 17 This is a schematic diagram of the inverter structure in an embodiment of this application. See also... Figure 17 In this embodiment, an inverter 100 is provided, including an inverter circuit 102, a switching circuit 104, and a controller 106.

[0241] The switching circuit 104 includes a plurality of relays 202 that are respectively connected to the inverter circuit 102 and the power grid 200; the controller 106 is used to implement the steps of the voltage control method described above, or to implement the steps of the detection method described above.

[0242] In the aforementioned inverter, the controller 106 determines the connection method between the inverter 100 and the power grid 200, as well as the current three-phase voltage of the power grid 200. In both three-phase coupled control and three-phase independent control modes, the current control strategy for controlling inverter circuit 102 is determined, based on the current control strategy and the three-phase grid voltage. The output of the control inverter circuit 102 is used as the three-phase inverter voltage. Three-phase drive voltage, avoiding three-phase inverter voltage and three-phase grid voltage If the voltage difference between the two sides is too large, the instantaneous inrush current of the relay 202 in the switching circuit 104 will be too large, which will affect the life of the relay, reduce the voltage imbalance of the half bus, and improve the service life of the inverter.

[0243] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0244] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0245] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. Those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A voltage control method, characterized by, The voltage control method is applied to an inverter, the inverter comprising an inverter circuit and a switching circuit, the switching circuit comprising a plurality of relays respectively connecting the inverter circuit and a power grid; the voltage control method comprising: in a case where the plurality of relays are in a detection state, obtaining a wiring mode between the inverter and the power grid; determining a current control strategy for controlling the inverter circuit according to the wiring mode and a current three-phase grid voltage of the power grid, the current control strategy comprising one of a three-phase coupled control mode and a three-phase independent control mode; controlling the inverter circuit to output a three-phase drive voltage as a three-phase inverter voltage of the inverter according to the current control strategy and the three-phase grid voltage; wherein a first state of the relays is determined based on the three-phase grid voltage and the three-phase inverter voltage, the first state comprising a normal working state and a fault state; the determining the current control strategy for controlling the inverter circuit according to the wiring mode and the current three-phase grid voltage of the power grid comprises: in a case where the wiring mode is a four-wire mode, obtaining a maximum unbalance degree of the three-phase grid voltage according to the current three-phase grid voltage of the power grid; in a case where the maximum unbalance degree is less than or equal to a first threshold, determining the current control strategy as the three-phase coupled control mode; in a case where the maximum unbalance degree is greater than the first threshold, determining the current control strategy as the three-phase independent control mode; in a case where the wiring mode is a three-wire mode, determining the current control strategy as the three-phase coupled control mode.

2. The voltage control method according to claim 1, characterized by, the obtaining the maximum unbalance degree of the three-phase grid voltage according to the current three-phase grid voltage of the power grid in a case where the wiring mode is the four-wire mode comprises: obtaining a plurality of first difference values according to grid voltages of each phase in the three-phase grid voltage, the first difference value representing a voltage deviation between grid voltages of any two phases; determining the maximum unbalance degree of the three-phase grid voltage according to the plurality of first difference values.

3. The voltage control method according to claim 1, characterized by, the controlling the inverter circuit to output the three-phase drive voltage according to the current control strategy and the three-phase grid voltage comprises: in a case where the current control strategy is the three-phase coupled control mode, obtaining a first three-phase pulse modulation signal according to the three-phase grid voltage and a preset d-axis voltage to control the inverter circuit to output the three-phase drive voltage; and / or in a case where the current control strategy is the three-phase independent control mode, obtaining a first three-phase pulse modulation signal corresponding to each phase of the grid voltage according to the grid voltage of each phase in the three-phase grid voltage and a first modulation ratio coefficient to control the inverter circuit to output the three-phase drive voltage.

4. The voltage control method according to any one of claims 1 to 3, characterized by, the controlling the inverter circuit to output the three-phase drive voltage according to the current control strategy, the three-phase grid voltage, an inverter current of each phase in a current three-phase inverter current of the inverter circuit and a second modulation ratio coefficient comprises: controlling the inverter circuit to output the three-phase drive voltage according to the current control strategy, the three-phase grid voltage, the inverter current of each phase in the current three-phase inverter current of the inverter circuit and the second modulation ratio coefficient.

5. The voltage control method according to claim 4, characterized by, The method comprises: obtaining a first three-phase pulse modulation signal corresponding to the three-phase grid voltage according to the current control strategy and the three-phase grid voltage; obtaining a second three-phase pulse modulation signal according to the three-phase inverter current and the second modulation ratio coefficient; controlling the inverter circuit to output the three-phase driving voltage according to the first three-phase pulse modulation signal and the second three-phase pulse modulation signal.

6. A method of detection, characterized in that The application is applied to an inverter, which comprises an inverter circuit and a switching circuit, and the switching circuit comprises a plurality of relays respectively connecting the inverter circuit and a grid; the detection method comprises: controlling the inverter circuit to output a three-phase driving voltage as a three-phase inverter voltage of the inverter according to the voltage control method in any one of claims 1 to 5 when the plurality of relays are in an off state; acquiring a three-phase output voltage of an output end of the inverter as the three-phase inverter voltage when the plurality of relays are in an on state and the inverter stops working; determining a first state of the relays according to the three-phase inverter voltage and the three-phase grid voltage.

7. The detection method according to claim 6, characterized in that, The method comprises: obtaining a first voltage difference according to the three-phase driving voltage output by the inverter circuit and the three-phase grid voltage; obtaining a second voltage difference according to the three-phase inverter voltage and the three-phase grid voltage when the inverter stops working; determining that the relays are in a normal working state when the first voltage difference is less than a first voltage threshold and the second voltage difference is less than a second voltage threshold.

8. The detection method according to claim 6, characterized in that, The detection method further comprises: controlling the plurality of relays to be in the off state and controlling the inverter circuit to stop working in response to the current three-phase inverter current of the inverter and a second state of the plurality of relays satisfying a preset condition when the inverter circuit outputs the three-phase driving voltage; wherein the second state comprises an off state and an on state.

9. The detection method according to claim 8, characterized in that, The method comprises: determining that the three-phase inverter current and the second state of the relays satisfy the preset condition when each of the relays is in the on state and the absolute value of the three-phase inverter current is greater than a first preset current; determining that the three-phase inverter current and the second state of the relays satisfy the preset condition when the relays are in the off state and at least one of the absolute values of the three-phase inverter current is greater than or equal to a second threshold.

10. An inverter, characterized by comprising: The application comprises: an inverter circuit; a switching circuit comprising a plurality of relays respectively connecting the inverter circuit and a grid; A controller for implementing the steps of the voltage control method of any one of claims 1 to 5, or for implementing the steps of the detection method of any one of claims 6-9.

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