Grid-connected relay control method and device and energy storage inverter circuit

Abstract

The embodiment of the invention discloses a grid-connected relay control method and device and an energy storage inverter circuit. The grid-connected relay control method is used for the grid-connected relay control device, the grid-connected relay control device is connected with a grid-connected relay of an energy storage inverter circuit, the energy storage inverter circuit comprises a power supply, a load and the grid-connected relay, the power supply, the load and a first end of the grid-connected relay are connected to a first node, and a second end of the grid-connected relay is connected to a second node. The second end of the grid-connected relay and the power grid are connected to a second node; the grid-connected relay control method comprises the following steps: closing a grid-connected relay connected with an N phase of a second node; obtaining a first voltage of at least one phase of the three-phase voltage of the second node; controlling the target relay to be closed according to the difference between the first voltage and a preset threshold voltage; the target relay is a grid-connected relay connected with the phase line of which the amplitude of the first voltage is equal to the preset threshold voltage. According to the technical scheme provided by the embodiment, arc discharge of the grid-connected relay during grid connection is avoided, and the service life of the grid-connected relay is prolonged.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of grid-connected control, and in particular to a grid-connected relay control method, device and energy storage inverter circuit. Background Art

[0002] With the strategic adjustment of the national photovoltaic industry, in order to achieve the national development goal of carbon neutrality by 2060, the photovoltaic energy storage system has ushered in a high-growth period of the industry, the installed capacity of energy storage systems has grown exponentially, and a large number of energy storage photovoltaic power stations have been built. The energy storage inverters used in existing energy storage systems generally have both grid-connected and off-grid functions, and can be switched between grid-connected and off-grid according to real-time working conditions.

[0003] When switching, it is necessary to use inverter relays and grid-connected relays to control grid-connected power generation or off-grid independent operation. When switching, it is difficult to avoid switching when the voltage across the relay contacts is not zero, and it is also difficult to avoid arcing between the contacts, which reduces the service life of the grid-connected relay and increases the cost of after-sales maintenance.

[0004] The existing control method of the grid-connected relay has the problem that arcing is easy to occur between the contacts of the grid-connected relay when the relay is switched to the grid, which reduces the life of the grid-connected relay and becomes a technical problem that needs to be solved urgently in the industry. Summary of the invention

[0005] The embodiments of the present invention provide a grid-connected relay control method, device and energy storage inverter circuit to solve the problem that arcing is easy to occur between contacts of the grid-connected relay, thereby reducing the life of the grid-connected relay.

[0006] In order to achieve the above technical problems, the present invention adopts the following technical solutions:

[0007] The embodiment of the present invention provides a grid-connected relay control method, which is used for a grid-connected relay control device, wherein the grid-connected relay control device is connected to a grid-connected relay of an energy storage inverter circuit, wherein the energy storage inverter circuit includes: a power supply, a load, and a grid-connected relay, wherein the power supply and the load and a first end of the grid-connected relay are connected to a first node, and a second end of the grid-connected relay is connected to a power grid at a second node;

[0008] The grid-connected relay control method comprises:

[0009] closing the grid-connected relay connected to the N phase of the second node;

[0010] Acquire a first voltage of at least one phase of the three-phase voltage of the second node;

[0011] Control the target relay to close according to the difference between the first voltage and the preset threshold voltage; the target relay is the grid-connected relay connected to the phase line where the amplitude of the first voltage is equal to the preset threshold voltage.

[0012] Optionally, the obtaining of the first voltage of at least one phase of the three-phase voltage of the second node includes:

[0013] Obtain the A-phase voltage of the power grid of the second node;

[0014] And / or, obtain the B-phase voltage of the power grid of the second node;

[0015] And / or, obtain the C-phase voltage of the power grid of the second node.

[0016] Optionally, the grid-connected relay includes a grid-side relay, the grid-side relay includes an A-phase grid-side relay, a B-phase grid-side relay and a C-phase grid-side relay, and the A-phase grid-side relay, the B-phase grid-side relay and the C-phase grid-side relay are respectively connected to the phase lines of the power grid at the second node; the first voltage includes at least one of the A-phase voltage, the B-phase voltage and the C-phase voltage;

[0017] The controlling the target relay to close according to the difference between the first voltage and the preset threshold voltage includes:

[0018] When the absolute value of the amplitude of the A-phase voltage is equal to the preset threshold voltage, control the A-phase grid-side relay to be powered on and closed;

[0019] When the absolute value of the amplitude of the B-phase voltage is equal to the preset threshold voltage, control the B-phase grid-side relay to be powered on and closed;

[0020] When the absolute value of the amplitude of the C-phase voltage is equal to the preset threshold voltage, control the C-phase grid-side relay to be powered on and closed; the preset threshold voltage includes 0V.

[0021] Optionally, the grid-side relay further includes an N-phase grid-side relay, the N-phase grid-side relay;

[0022] The closing of the grid-connected relay connected to the N phase of the second node includes:

[0023] Close the N-phase grid-side relay connected to the N phase of the second node.

[0024] Optionally, the grid-connected relay further includes an inverter-side relay, and the inverter-side relay includes an N-phase inverter-side relay, an A-phase inverter-side relay, a B-phase inverter-side relay, and a C-phase inverter-side relay; the N-phase inverter-side relay, the A-phase inverter-side relay, the B-phase inverter-side relay, and the C-phase inverter-side relay are respectively connected to the respective phase lines of the power supply and the respective phase lines of the load at a first node;

[0025] Before closing the grid-connected relay connected to the N phase of the second node, it further includes:

[0026] Closing the N-phase inverter-side relay connected to the N phase of the first node;

[0027] Closing the A-phase inverter-side relay connected to the A phase of the first node;

[0028] Closing the B-phase inverter-side relay connected to the B phase of the first node;

[0029] Closing the C-phase inverter-side relay connected to the C phase of the first node.

[0030] Optionally, before closing the grid-connected relay connected to the N phase of the second node, it further includes:

[0031] Determining that the grid-connected relay meets the grid connection conditions;

[0032] Determining that the grid-connected relay control device and the energy storage inverter circuit are free of faults.

[0033] Optionally, the determining that the grid-connected relay meets the grid connection conditions includes:

[0034] After controlling the energy storage inverter circuit to operate in open loop for a first preset time, perform phase-locked loop operation;

[0035] When the open-loop voltage and phase of the energy storage inverter circuit are respectively the same as the voltage and phase of the power grid, it is determined that the grid-connected relay meets the grid connection conditions.

[0036] Optionally, the grid-connected relay control device includes a first sampling control unit and a second sampling control unit. The first sampling control unit and the second sampling control unit are respectively connected to the grid-connected relay, and the first sampling control unit and the second sampling control unit are communicatively connected;

[0037] The controlling the target relay to close according to the difference between the first voltage and the preset threshold voltage includes:

[0038] Controlling the target relay to close by the first sampling control unit according to the difference between the first voltage and the preset threshold voltage;

[0039] After controlling the target relay to close according to the difference between the first voltage and the preset threshold voltage, the method further includes:

[0040] When the first sampling control unit is in a preset working condition, the second sampling control unit is used to maintain the grid-connected relay in a closed state;

[0041] When a fault occurs in the grid-connected relay control device or the energy storage inverter circuit, the first sampling control unit or the second sampling control unit controls the grid-connected relay to power off according to the fault state of the grid-connected relay control device or the energy storage inverter circuit.

[0042] According to another aspect of the present invention, an embodiment of the present invention provides a grid-connected relay control device, which is connected to the control end of the grid-connected relay of the energy storage inverter circuit. The energy storage inverter circuit includes: a power supply, a load, and a grid-connected relay. The power supply is connected to the load and the first end of the grid-connected relay at a first node, and the second end of the grid-connected relay is connected to the power grid at a second node;

[0043] The grid-connected relay control device includes:

[0044] A sampling control module, connected to the second node, for obtaining at least one first voltage of the three-phase voltage of the second node; generating a control signal according to the difference between the first voltage and the preset threshold voltage;

[0045] A control module, connected to the sampling control module and the control end of the grid-connected relay. The control module is used to control the grid-connected relay connected to the N phase of the second node to close, and control the target relay to close according to the control signal; the target relay is the grid-connected relay connected to the phase line where the amplitude of the first voltage is equal to the preset threshold voltage.

[0046] Optionally, the grid-connected relay includes a grid-side relay. The grid-side relay includes an A-phase grid-side relay, a B-phase grid-side relay, and a C-phase grid-side relay. The A-phase grid-side relay, the B-phase grid-side relay, and the C-phase grid-side relay are respectively connected to the phase lines of the power grid at the second node; the first voltage includes at least one of the A-phase voltage, the B-phase voltage, and the C-phase voltage;

[0047] The sampling control module is specifically used to generate a first control signal when the absolute value of the amplitude of the A-phase voltage is equal to the preset threshold voltage; the control module is used to control the A-phase grid-side relay to be powered on and closed according to the first control signal;

[0048] The sampling control module is configured to generate a second control signal when the absolute value of the amplitude of the B-phase voltage is equal to the preset threshold voltage; the control module is configured to control the B-phase grid-side relay to be powered on and closed according to the second control signal;

[0049] The sampling control module is configured to generate a third control signal when the absolute value of the amplitude of the C-phase voltage is equal to the preset threshold voltage; the control module is configured to control the C-phase grid-side relay to be powered on and closed according to the third control signal; the preset threshold voltage includes 0V.

[0050] Optionally, the sampling control module includes a first sampling control unit and a second sampling control unit. The first sampling control unit and the second sampling control unit are respectively connected to the grid-connected relay, and the first sampling control unit and the second sampling control unit are communicatively connected;

[0051] The first sampling control unit is configured to generate a control signal according to the difference between the first voltage and the preset threshold voltage, and control the target relay to be closed through the control module;

[0052] The second sampling control unit is configured to maintain the closed state of the grid-connected relay through the control module when the first sampling control unit is in a preset working condition;

[0053] The first sampling control unit or the second sampling control unit is further configured to control the grid-connected relay to be powered off through the control module according to the fault state of the grid-connected relay control device or the energy storage inverter circuit when the grid-connected relay control device or the energy storage inverter circuit fails.

[0054] According to another aspect provided by the present invention, an embodiment of the present invention provides an energy storage inverter circuit, including: a power supply, a load, and a grid-connected relay. The power supply is connected to the load and the first end of the grid-connected relay at a first node. The second end of the grid-connected relay is connected to the grid at a second node. The control end of the grid-connected relay is connected to the grid-connected relay control device proposed in any item of the second aspect, and / or, the grid-connected relay is controlled by the grid-connected relay control method proposed in any item of the first aspect.

[0055] The grid-connected relay control method provided by the embodiment of the present invention first closes the grid-connected relay connected to the N phase of the second node, and then obtains the first voltage of at least one phase of the three-phase voltage of the second node. According to the difference between the first voltage and the preset threshold voltage, the target relay is controlled to close. With such a setting, the grid-connected relay connected to the phase line where the amplitude of the first voltage is equal to the preset threshold voltage can be closed when there is no current flowing through the contact, thereby avoiding arcing when the grid-connected relay is closed, improving the thermal stability of the grid-connected relay, and thus extending the service life of the grid-connected relay. Description of the Drawings

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description in the embodiments of the present invention. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the content of the embodiments of the present invention and these drawings.

[0057] Figure 1 is a flowchart of a grid-connected relay control method provided by an embodiment of the present invention;

[0058] Figure 2 is a schematic structural diagram of a grid-connected relay control device provided by an embodiment of the present invention;

[0059] Figure 3 is a flowchart of another grid-connected relay control method provided by an embodiment of the present invention;

[0060] Figure 4 is a flowchart of yet another grid-connected relay control method provided by an embodiment of the present invention;

[0061] Figure 5 is a flowchart of yet another grid-connected relay control method provided by an embodiment of the present invention;

[0062] Figure 6 is a flowchart of yet another grid-connected relay control method provided by an embodiment of the present invention;

[0063] Figure 7 is a schematic structural diagram of another grid-connected relay control device provided by an embodiment of the present invention;

[0064] Figure 8 is a schematic structural diagram of an energy storage inverter circuit provided by an embodiment of the present invention;

[0065] Figure 9 is a flowchart of yet another grid-connected relay control method provided by an embodiment of the present invention. Detailed Embodiments

[0066] To enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0067] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily need to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0068] Based on the above technical problems, the following solutions are proposed in this embodiment:

[0069] Figure 1 It is a flowchart of a grid-connected relay control method provided by an embodiment of the present invention. Figure 2 It is a schematic structural diagram of a grid-connected relay control device provided by an embodiment of the present invention. Combining Figure 1 and Figure 2 , the grid-connected relay control method provided by the embodiment of the present invention is used for the grid-connected relay control device 100. The grid-connected relay control device 100 is connected to the grid-connected relay 23 of the energy storage inverter circuit 200. The energy storage inverter circuit 200 includes: a power supply 21, a load 22, and a grid-connected relay 23. The power supply 21 is connected to the load 22 and the first end of the grid-connected relay 23 at a first node N1, and the second end of the grid-connected relay 23 is connected to the power grid at a second node N2.

[0070] The grid-connected relay control method provided by the embodiment of the present invention includes:

[0071] S101. Close the grid-connected relay 23 connected to the N phase of the second node N2.

[0072] Specifically, since the three phases A, B, and C represent the three phase lines of three-phase alternating current, namely phase A, phase B, and phase C. The phase differences between phase A, phase B, and phase C are 120° to each other. Phase N is the neutral point lead-out wire of the three-phase power supply 21 and belongs to the common circuit of the three-phase system. Phase N is used to balance the three-phase current and detect the zero-sequence current.

[0073] When controlling the grid-connected relay 23, the grid-connected relay 23 connected to phase N on the grid side can be closed. There is no voltage difference on phase N. With such a setting, there will be no potential difference across the contacts of the grid-connected relay 23, thus not affecting the lifespan of the grid-connected relay 23.

[0074] S102. Obtain a first voltage of at least one phase of the three-phase voltage of the second node N2.

[0075] Specifically, since the three phases A, B, and C are AC voltages, there is likely to be a voltage difference between the contact switches of the grid-connected relay 23, which is likely to cause ablation of the contacts of the grid-connected relay 23. Obtain the voltage of at least one phase of the three-phase voltage of the second node N2 where the grid-connected relay 23 is connected to the three phases A, B, and C of the grid. The voltage of at least one phase among the phase voltages of phase A, phase B, or phase C on one side of the first node N1 of the grid-connected relay 23 can be obtained.

[0076] S103. Control the target relay to close according to the difference between the first voltage and a preset threshold voltage; the target relay is the grid-connected relay 23 connected to the phase line where the amplitude of the first voltage is equal to the preset threshold voltage.

[0077] Specifically, the target relay can be the grid-connected relay 23 connected to the phase line corresponding to the first voltage that meets the closing condition. The closing condition means that the first voltage is equal to the preset threshold voltage.

[0078] The preset threshold voltage can be set as needed. The preset threshold voltage can be zero volts or a voltage close to the zero-crossing point of the ABC three-phase voltages. Since the amplitude of the first voltage of the second node N2 is too large, when the grid-connected relay 23 is closed, current is likely to flow, causing an arc to be generated when the contacts of the grid-connected relay 23 are closed, which may ablate the grid-connected relay 23 and affect the lifespan of the grid-connected relay 23. By comparing the first voltage of the second node N2 where the grid-connected relay 23 is connected to the grid with the preset threshold voltage, when the first voltage is equal to the preset threshold voltage, the grid-connected relay 23 on the corresponding phase line can be closed, so that when the grid-connected relay 23 is closed, the voltage difference across its contacts is zero or close to zero, thus there is no voltage difference across the contacts of the grid-connected relay 23 and no current flows. At this time, when the contacts of the grid-connected relay 23 are closed, no arc will be generated, thereby better avoiding the thermal failure problem of the contacts of the grid-connected relay 23 caused by arcing, and further extending the service life of the grid-connected relay 23.

[0079] The grid-connected relay control method provided in this embodiment first closes the grid-connected relay 23 connected to the N phase of the second node N2, and then obtains the first voltage of at least one phase of the three-phase voltages of the second node N2. According to the difference between the first voltage and the preset threshold voltage, the target relay is controlled to close. With this setting, the grid-connected relay 23 connected to the phase line where the amplitude of the first voltage is equal to the preset threshold voltage can be closed when there is no current flowing through its contacts, thus avoiding arcing when the grid-connected relay 23 is closed, improving the thermal stability of the grid-connected relay 23, and further extending the service life of the grid-connected relay 23.

[0080] Optionally, on the basis of the above embodiment, the obtaining the first voltage of at least one phase of the three-phase voltages of the second node N2 includes: obtaining the A-phase voltage of the grid of the second node N2; and / or, obtaining the B-phase voltage of the grid of the second node N2; and / or, obtaining the C-phase voltage of the grid of the second node N2.

[0081] Optionally, Figure 3 is a flowchart of another grid-connected relay control method provided by an embodiment of the present invention. On the basis of the above embodiment, in combination with Figure 2 and Figure 3 , the grid-connected relay 23 includes a grid-side relay, and the grid-side relay includes an A-phase grid-side relay, a B-phase grid-side relay, and a C-phase grid-side relay. The A-phase grid-side relay, the B-phase grid-side relay, and the C-phase grid-side relay are respectively connected to the phase lines of the grid at the second node N2; the first voltage includes at least one of the A-phase voltage, the B-phase voltage, and the C-phase voltage.

[0082] In combination withFigure 2 and Figure 3 , the grid-connected relay control method provided by the embodiments of the present invention includes:

[0083] S101. Close the grid-connected relay 23 connected to the N phase of the second node N2.

[0084] S102. Obtain a first voltage of at least one phase of the three-phase voltage of the second node N2.

[0085] S201. When the absolute value of the amplitude of the A-phase voltage is equal to the preset threshold voltage, control the A-phase grid-side relay to be powered on and closed.

[0086] Specifically, according to the A-phase voltage of the power grid of the second node N2, it can be determined whether the A-phase voltage of the power grid of the second node N2 is a zero-crossing point. When the A-phase voltage of the power grid of the second node N2 is a zero-crossing point, close the contact of the grid-connected relay 23 connected to the phase line corresponding to the A-phase voltage of the power grid of the second node N2.

[0087] S202. When the absolute value of the amplitude of the B-phase voltage is equal to the preset threshold voltage, control the B-phase grid-side relay to be powered on and closed.

[0088] Specifically, according to the B-phase voltage of the power grid of the second node N2, it can be determined whether the B-phase voltage of the power grid of the second node N2 is a zero-crossing point. When the B-phase voltage of the power grid of the second node N2 is a zero-crossing point, close the contact of the grid-connected relay 23 connected to the phase line corresponding to the B-phase voltage of the power grid of the second node N2.

[0089] S203. When the absolute value of the amplitude of the C-phase voltage is equal to the preset threshold voltage, control the C-phase grid-side relay to be powered on and closed; the preset threshold voltage includes 0V.

[0090] Specifically, according to the C-phase voltage of the power grid of the second node N2, it can be determined whether the C-phase voltage of the power grid of the second node N2 is a zero-crossing point. When the C-phase voltage of the power grid of the second node N2 is a zero-crossing point, close the contact of the grid-connected relay 23 connected to the phase line corresponding to the C-phase voltage of the power grid of the second node N2.

[0091] Another optional implementation manner, in combination with Figure 2 and Figure 3, based on the phase A voltage, phase B voltage, and phase C voltage of the power grid at the second node N2, it can be determined which phase voltage of which line passes through the zero point first, and then the grid-connected relay 23 of that phase is closed first. With this setting, the energy storage inverter circuit 200 temporarily operates in a single-phase mode. Since the grid-connected relay 23 is closed at the zero crossing point, there will be no voltage across the contacts of the relay, and no current will flow through the contacts. In this way, there will be no arcing between the contacts of the grid-connected relay 23, and no thermal failure phenomenon will occur. Similarly, then detect which phase voltage of the remaining two phases reaches the zero crossing point first, and close the grid-connected relay 23 of the corresponding phase first, and so on, until all the grid-connected relays 23 of the three phases are closed to achieve three-phase grid connection operation.

[0092] Optionally, on the basis of the above embodiment, in combination with Figure 2 and Figure 3 , the grid-side relay further includes an N-phase grid-side relay, and the N-phase grid-side relay. Step S101, closing the grid-connected relay 23 connected to the N phase of the second node N2 may include: closing the N-phase grid-side relay connected to the N phase of the second node N2.

[0093] Specifically, the N-phase grid-side relay of the grid-connected relay 23 is connected to the N phase of the power grid at the second node N2 of the N phase. Since there is no current flowing through the N-phase line during grid connection, the N-phase grid-side relay connected to the N phase of the second node N2 can be closed first, which can not only achieve the closing of the N-phase grid-side relay, but also prevent arcing or thermal runaway of the grid-side relay connected to the N phase. Without affecting the service life of the grid-connected relay 23, the control efficiency of the grid-connected relay 23 is improved.

[0094] Optionally, on the basis of the above embodiment, in combination with Figure 2 and Figure 3 , the grid-connected relay 23 further includes an inverter-side relay, and the inverter-side relay includes an N-phase inverter-side relay, an A-phase inverter-side relay, a B-phase inverter-side relay, and a C-phase inverter-side relay; the N-phase inverter-side relay, the A-phase inverter-side relay, the B-phase inverter-side relay, and the C-phase inverter-side relay are respectively connected to the respective phase lines of the power supply 21 and the respective phase lines of the load 22 at the first node N1.

[0095] Figure 4 is a flowchart of another grid-connected relay control method provided by an embodiment of the present invention. On the basis of the above embodiment, in combination with Figure 2 and Figure 4 , the grid-connected relay control method provided by the embodiment of the present invention includes:

[0096] S301. Close the N-phase inverter-side relay connected to the N-phase of the first node N1.

[0097] S302. Close the A-phase inverter-side relay connected to the A-phase of the first node N1.

[0098] S303. Close the B-phase inverter-side relay connected to the B-phase of the first node N1.

[0099] S304. Close the C-phase inverter-side relay connected to the C-phase of the first node N1.

[0100] Specifically, the inverter-side relay is connected to the power supply 21 of the energy storage inverter circuit 200. The power supply 21 of the energy storage inverter circuit 200 may include a battery and / or a photovoltaic power supply 21. The power supply 21 of the energy storage inverter circuit 200 may further include an inverter module that inverses the DC voltage output by the battery and / or the photovoltaic power supply 21 into an AC voltage. Since the relay on the inverter side is connected to the AC output side of the inverter module, rather than the grid side, the inverter-side relay can be closed before closing the grid-side inverter. The order of closing the inverter-side relay may not be limited. The N-phase inverter-side relay connected to the N-phase of the first node N1 can be closed first as needed. Then, the A-phase inverter-side relay connected to the A-phase of the first node N1 is closed in sequence. The B-phase inverter-side relay connected to the B-phase of the first node N1 is closed. The C-phase inverter-side relay connected to the C-phase of the first node N1 is closed.

[0101] S101. Close the grid-connected relay 23 connected to the N-phase of the second node N2.

[0102] S102. Obtain a first voltage of at least one phase of the three-phase voltage of the second node N2.

[0103] S103. Control the target relay to close according to the difference between the first voltage and a preset threshold voltage; the target relay is the grid-connected relay 23 connected to the phase line where the amplitude of the first voltage is equal to the preset threshold voltage.

[0104] Optionally, Figure 5 is a flowchart of another grid-connected relay control method provided by an embodiment of the present invention. On the basis of the above embodiment, in combination with Figure 2 and Figure 5 , the grid-connected relay control method provided by the embodiment of the present invention includes:

[0105] Before closing the grid-connected relay 23 connected to the N-phase of the second node N2, it further includes:

[0106] S401. Determine that the grid-connected relay 23 meets the grid connection conditions.

[0107] Specifically, since an inverter relay may be connected between the inverter module of the energy storage inverter circuit 200 and the load 22. Before the inverter relay is powered on and operates, it is possible to first detect whether there is a stuck phenomenon in the inverter relay. When it is determined that there is no stuck phenomenon in the inverter relay, control the inverter module to output an AC drive voltage to operate. Before controlling the grid-connected relay 23 to close, it is also necessary to operate the inverter module in open loop and, through the working state of the phase-locked loop, make the open-loop voltage and phase of the inverter module the same in frequency, amplitude, and phase as the voltage and phase of the power grid.

[0108] S402. Determine that the grid-connected relay control device 100 and the energy storage inverter circuit 200 are free of faults.

[0109] Specifically, the grid-connected relay 23 can be closed only when both the energy storage inverter circuit 200 and the grid-connected relay control device 100 are free of faults. Such a setting preferably avoids the power grid anomaly caused by the fault of the energy storage inverter circuit 200 or the grid-connected relay control device 100 and ensures the safe operation of the power grid.

[0110] S101. Close the grid-connected relay 23 connected to the N phase of the second node N2.

[0111] S102. Obtain the first voltage of at least one phase of the three-phase voltage of the second node N2.

[0112] S103. Control the target relay to close according to the difference between the first voltage and the preset threshold voltage; the target relay is the grid-connected relay 23 connected to the phase line where the amplitude of the first voltage is equal to the preset threshold voltage.

[0113] An optional implementation manner, combined with Figure 2 and Figure 5 , the determination that the grid-connected relay 23 meets the grid connection conditions includes: after controlling the energy storage inverter circuit 200 to operate in open loop for a first preset time, perform phase-locked loop operation; when the open-loop voltage and phase of the energy storage inverter circuit 200 are respectively the same as the voltage and phase of the power grid, determine that the grid-connected relay 23 meets the grid connection conditions.

[0114] Specifically, the first preset time can be set as needed. After the energy storage inverter circuit 200 operates in open loop for the first preset time and is in a stable switching operation state, it is convenient to perform phase-locked loop operation on the energy storage inverter circuit 200, so that the open-loop voltage of the energy storage inverter circuit 200 is consistent with the voltage of the power grid, and the phase of the open-loop voltage of the energy storage inverter circuit 200 is consistent with the phase of the voltage of the power grid, enabling the energy storage inverter circuit 200 to have the conditions for grid connection or off-grid operation.

[0115] Optionally, the grid-connected relay control device 100 includes a first sampling control unit and a second sampling control unit. The first sampling control unit and the second sampling control unit are respectively connected to the grid-connected relay 23, and the first sampling control unit and the second sampling control unit are communicatively connected.

[0116] Figure 6 It is a flowchart of another grid-connected relay control method provided by an embodiment of the present invention. Figure 7 It is a schematic structural diagram of another grid-connected relay control device provided by an embodiment of the present invention. On the basis of the above embodiments, combined with Figure 6 and Figure 7 , the grid-connected relay control method provided by the embodiment of the present invention includes:

[0117] S401. Determine that the grid-connected relay 23 meets the grid connection conditions.

[0118] S402. Determine that the grid-connected relay control device 100 and the energy storage inverter circuit 200 are free of faults.

[0119] Specifically, when the grid-connected relay control device 100 has a fault, it is necessary to disconnect the grid-connected relay 23 to prevent the fault of the grid-connected relay control device 100 from spreading to the power grid. When the energy storage inverter circuit 200 has a fault, it is necessary to disconnect the grid-connected relay 23 to prevent the fault of the energy storage inverter circuit 200 from spreading to the power grid. Only when it is ensured that both the energy storage inverter circuit 200 and the grid-connected relay control device 100 are free of faults can the grid-connected relay 23 be controlled to close.

[0120] S101. Close the grid-connected relay 23 connected to the N phase of the second node N2.

[0121] S102. Obtain a first voltage of at least one phase of the three-phase voltage of the second node N2.

[0122] S501. Control the target relay to close according to the difference between the first voltage and a preset threshold voltage by the first sampling control unit 611.

[0123] Specifically, the first sampling control unit 611 can collect the first voltage of the second node N2. The first sampling control unit 611 can also compare the collected first voltage with the preset threshold voltage, and thus close the grid-connected relay 23 connected to the phase line where the first voltage is equal to the preset threshold voltage as the target relay.

[0124] S502. When the first sampling control unit 611 is in a preset working condition, maintain the closed state of the grid-connected relay 23 through the second sampling control unit 612.

[0125] Specifically, the preset working conditions may include: when the first sampling control unit 611 needs to shut down actively or has a fault and must shut down, or when grid connection / disconnection switching is required, or when program upgrade and reset are needed. At this time, if the power grid is normal and there are working conditions such as a load 22 in the energy storage inverter circuit 200. Under the above preset working conditions, the user of the load 22 does not want the grid connection relay 23 to trip, thereby causing the load 22 to lose power.

[0126] The second sampling control unit 612 can communicate with the first sampling control unit 611 to maintain the grid connection relay 23 in a closed state through the second sampling control unit 612.

[0127] S503. When a fault occurs in the grid connection relay control device 100 or the energy storage inverter circuit 200, the first sampling control unit 611 or the second sampling control unit 612 controls the grid connection relay 23 to cut off power according to the fault state of the grid connection relay control device 100 or the energy storage inverter circuit 200.

[0128] Specifically, when a fault occurs in the grid connection relay control device 100, or a fault occurs in the energy storage inverter circuit 200, or faults occur in both the grid connection relay control device 100 and the energy storage inverter circuit 200, the first sampling control unit 611 can control the grid connection relay 23 to cut off power. When the first sampling control unit 611 is not working under the preset working conditions, the second sampling control unit 612 can control the grid connection relay 23 to cut off power. When a fault occurs while the second sampling control unit 612 maintains the grid connection relay 23 in a closed state, the first sampling control unit 611 can also take back the control right from the second sampling control unit 612, so that the first sampling control unit 611 controls the grid connection relay 23 to cut off power.

[0129] Exemplarily, Figure 8 is a flowchart of another grid connection relay control method provided by an embodiment of the present invention. Figure 9 is a schematic structural diagram of an energy storage inverter circuit provided by an embodiment of the present invention. Combining Figure 8 and Figure 9 , the grid connection relay control method provided by this embodiment includes: the first sampling control unit 611 may include a DSP control unit, and the second sampling control unit 612 may include an MCU control unit. The energy storage inverter circuit 200 is powered on. The DSP (Digital Signal Processor) control unit and the MCU (Microcontroller Unit) control unit are reset.

[0130] After the DSP control unit and the MCU control unit are reset, the DSP control unit starts self-checking. After passing the self-check, the DSP control unit starts sampling the grid-side first voltage of the second node N2, the inverter-side voltage of the first node N1, the load 22 voltage, and the inverter-side current. The MCU control unit starts sampling the inverter-side voltage and the inverter-side current of the first node N1. The MCU control unit and the DSP control unit maintain communication simultaneously.

[0131] When the DSP detects the grid voltage and determines that it meets the grid-connection working conditions, it starts the inverter output operation. Before closing the inverter relay, it detects whether the inverter relay is normal, such as detecting whether there is a sticking phenomenon of the inverter relay. If the inverter relay is normal, the inverter module starts open-loop operation. After the open-loop operation starts, the DSP control module starts the phase-locked loop operation.

[0132] When the open-loop voltage and phase of the inverter module are consistent with the grid voltage and phase, first close the grid-side N-phase grid-connection relay 23, and then determine which phase of the first voltages of the ABC three phases on the grid side passes through the zero-crossing first, and close the grid-connection relay 23 of that phase first. With this setting, the energy storage inverter circuit 200 temporarily operates in the single-phase mode. Since the grid-connection relay 23 is closed at the zero-crossing point, there will be no voltage across the contacts of the grid-connection relay 23 and no current will flow through the contacts. With this setting, there will be no arcing between the contacts of the grid-connection relay 23 and no thermal failure phenomenon will occur. Similarly, then detect which phase of the remaining two phases reaches the zero-crossing first, and close the grid-connection relay 23 of the corresponding phase first. And so on, until all three-phase grid-connection relays 23 are closed to achieve three-phase grid connection operation.

[0133] During the grid-connection process, if a fault occurs, the DSP control unit and the MCU control unit will disconnect all the grid-connection relays 23 and the inverter relay to perform protective shutdown. Among them, Grid_Rely_Ctrl_K8, Grid_Rely_Ctrl_K9, Grid_Rely_Ctrl_K2, Grid_Rely_Ctrl_K4, Grid_Rely_Ctrl_K6, and Dsp_RlyHold are control signals output by the DSP control unit. MCU_RlyHold and MCU_Rly12V are control signals output by the MCU control unit.

[0134] When active shutdown is required, or there is a fault that necessitates shutdown, or grid disconnection and switching is needed, or the DSP control unit requires program upgrade and reset. If the power grid is normal at this time and the energy storage inverter circuit 200 is connected to a load 22. The DSP control unit first communicates with the MCU control unit and transfers the control right to maintain the conduction state of the grid-connected relay 23 to the MCU control unit. That is, Grid_Rely_Ctrl_K8 is set to 0, Grid_Rely_Ctrl_K9 is set to 0, Grid_Rely_Ctrl_K2 is set to 0, Grid_Rely_Ctrl_K4 is set to 0, Grid_Rely_Ctrl_K6 is set to 0, MCU_RlyHold is set to 0, Dsp_RlyHold is set to 0, and MCU_Rly12V is set to 1. The MCU control unit is used to keep the grid-connected relay 23 in the closed state. At this time, the DSP control unit can be reset and upgraded without causing the load 22 to lose power, effectively ensuring the normal operation of the load 22 and improving the user experience.

[0135] During the period when the MCU control unit keeps the grid-connected relay 23 in the closed state, if a fault occurs or emergency grid disconnection operation is required, the MCU control unit can also actively disconnect the grid-connected relay 23, cut off the connection between the load 22 and the power grid, and perform protection operations. When the MCU control unit is used to keep the grid-connected relay 23 in the closed state, the DSP control unit can also actively communicate with the MCU control unit to take back the control right of the grid-connected relay 23, that is, perform a series of operations. Exemplarily, the MCU control unit and the DSP control unit can communicate through SCI, but it is not limited to SCI communication.

[0136] Continue to combine Figure 8 and Figure 9 , the grid-connected relay control method provided by this embodiment includes:

[0137] S901. Power on the machine.

[0138] S902. Reset the DSP control unit and reset the MCU control unit.

[0139] S903. Determine whether the DSP control unit and the MCU control unit have completed reset and self-check; if so, execute S904; if not, execute S909.

[0140] S904. Set MCU_Rly12V to 0, MCU_RlyHold to 0, Dsp_RlyHold to 0, Grid_Rely_Ctrl_K8 to 0, Grid_Rely_Ctrl_K9 to 0, Grid_Rely_Ctrl_K2 to 0, Grid_Rely_Ctrl_K4 to 0, Grid_Rely_Ctrl_K6 to 0.

[0141] S905. Determine whether the grid connection conditions are met; if so, execute S906; if not, execute S908.

[0142] S906. Control the inverter relay to close.

[0143] S907. Set MCU_RlyHold to 0, Dsp_RlyHold to 1, Grid_Rely_Ctrl_K8 to 1, Grid_Rely_Ctrl_K9 to 1, Grid_Rely_Ctrl_K2 to 1, Grid_Rely_Ctrl_K4 to 1, and Grid_Rely_Ctrl_K6 to 1. Then, execute S910.

[0144] S908. Wait for 100 ms.

[0145] S909. Wait for 54 s.

[0146] S910. Determine whether there is a fault; if so, execute S904; if not, execute S911.

[0147] S911. Set MCU_Rly12V to 1.

[0148] S912. Set Grid_Rely_Ctrl_K9 to 0.

[0149] S913. Determine whether there is a fault; if so, execute S904; if not, execute S914.

[0150] S914. Determine whether the A-phase of the first voltage of the second node N2 of the energy storage inverter circuit 200 is passing through the zero point; if so, execute S915; if not, execute S916 and execute S917.

[0151] S915. Control the grid connection relay 23 corresponding to the first voltage of the A-phase to close, and set Grid_Rely_Ctrl_K2 to 0.

[0152] S916. Determine whether there is a fault; if so, execute S904; if not, execute S917.

[0153] S917. Determine whether the B-phase of the first voltage of the second node N2 of the energy storage inverter circuit 200 is passing through the zero point; if so, execute S918; if not, execute S919 and execute S920.

[0154] S918. Control the grid connection relay 23 corresponding to the first voltage of the B-phase to close, and set Grid_Rely_Ctrl_K4 to 0.

[0155] S919. Determine whether there is a fault; if so, execute S904; if not, execute S920.

[0156] S920. Determine whether the C phase of the first voltage of the second node N2 of the energy storage inverter circuit 200 passes through the zero point; if so, execute S921.

[0157] S921. Control the grid-connected relay 23 corresponding to the first voltage of the C phase to close, and set Grid_Rely_Ctrl_K6 to 0.

[0158] S922. Determine whether there is a fault; if so, execute S904; if not, execute S923.

[0159] S923. Determine whether the A-phase grid-side relay is closed; if so, execute S924; if not, execute S914.

[0160] S924. Determine whether the B-phase grid-side relay is closed; if so, execute S925; if not, execute S917.

[0161] S925. Determine whether the C-phase grid-side relay is closed; if so, execute S926; if not, execute S920.

[0162] S926. Enter the grid-connected holding state of the DSP control unit, and set Dsp_RlyHold to 0.

[0163] S927. Determine whether the MCU control unit needs to hold; if so, execute S928; if not, execute S932.

[0164] S928. Set MCU_Rly12V to 1, set MCU_RlyHold to 0, set Dsp_RlyHold to 0, set Grid_Rely_Ctrl_K8 to 0, set Grid_Rely_Ctrl_K9 to 0, set Grid_Rely_Ctrl_K2 to 0, and set Grid_Rely_Ctrl_K4 to 0, and set Grid_Rely_Ctrl_K6 to 0.

[0165] S929. Determine whether shutdown is required; if so, execute S930; if not, execute S931.

[0166] S930. Set MCU_Rly12V to 1.

[0167] S931. Determine whether there is a fault; if so, execute S904; if not, execute S928.

[0168] S932. Determine whether there is a fault; if so, execute S904; if not, execute S926.

[0169] S933. Determine whether a restart is required; if so, execute S903; if not, execute S904.

[0170] It should be noted that setting Grid_Rely_Ctrl_K9 to 0 is used to control the closing of the N-phase grid-side relay. Setting Grid_Rely_Ctrl_K2 to 0 is used to control the closing of the A-phase grid-side relay. Setting Grid_Rely_Ctrl_K4 to 0 is used to control the closing of the B-phase grid-side relay. Setting Grid_Rely_Ctrl_K6 to 0 is used to control the closing of the C-phase grid-side relay. Setting Grid_Rely_Ctrl_K8 to 0 is used to control the closing of the inverter-side relay.

[0171] This embodiment provides a grid-connected relay control device 100. The grid-connected relay control device 100 is connected to the control terminal of the grid-connected relay 23 of the energy storage inverter circuit 200. The energy storage inverter circuit 200 includes: a power supply 21, a load 22, and a grid-connected relay 23. The power supply 21 is connected to the load 22 and the first end of the grid-connected relay 23 at a first node N1. The second end of the grid-connected relay 23 is connected to the grid at a second node N2. On the basis of the above embodiment, continue to refer to Figure 2 , the grid-connected relay control device 100 provided by the embodiment of the present invention includes:

[0172] A sampling control module 61, connected to the second node N2, for obtaining a first voltage of at least one phase of the three-phase voltage of the second node N2; generating a control signal according to the difference between the first voltage and a preset threshold voltage;

[0173] A control module 62, connected to the sampling control module 61 and the control terminal of the grid-connected relay 23. The control module 62 is used to control the grid-connected relay 23 connected to the N phase of the second node N2 to close, and control the target relay to close according to the control signal; the target relay is the grid-connected relay 23 connected to the phase line where the amplitude of the first voltage is equal to the preset threshold voltage.

[0174] Optionally, the grid-connected relay 23 includes grid-side relays. The grid-side relays include an A-phase grid-side relay, a B-phase grid-side relay, and a C-phase grid-side relay. The A-phase grid-side relay, the B-phase grid-side relay, and the C-phase grid-side relay are respectively connected to the phase lines of the grid at the second node N2; the first voltage includes at least one of the A-phase voltage, the B-phase voltage, and the C-phase voltage.

[0175] The sampling control module 61 is specifically configured to generate a first control signal when the absolute value of the amplitude of the phase-A voltage is equal to the preset threshold voltage; the control module 62 is configured to control the power-on and closing of the phase-A grid-side relay according to the first control signal.

[0176] The sampling control module 61 is configured to generate a second control signal when the absolute value of the amplitude of the phase-B voltage is equal to the preset threshold voltage; the control module 62 is configured to control the power-on and closing of the phase-B grid-side relay according to the second control signal.

[0177] The sampling control module 61 is configured to generate a third control signal when the absolute value of the amplitude of the phase-C voltage is equal to the preset threshold voltage; the control module 62 is configured to control the power-on and closing of the phase-C grid-side relay according to the third control signal; the preset threshold voltage includes 0V.

[0178] Optionally, on the basis of the above embodiments, continue to refer to Figure 7 The sampling control module 61 includes a first sampling control unit 611 and a second sampling control unit 612. The first sampling control unit 611 and the second sampling control unit 612 are respectively connected to the grid-connected relay 23, and the first sampling control unit 611 and the second sampling control unit 612 are communicatively connected; the first sampling control unit 611 is configured to generate a control signal according to the difference between the first voltage and the preset threshold voltage, and control the closing of the target relay through the control module 62. The second sampling control unit 612 is configured to maintain the closed state of the grid-connected relay 23 through the control module 62 when the first sampling control unit 611 is in a preset working condition. The first sampling control unit 611 or the second sampling control unit 612 is further configured to control the power-off of the grid-connected relay 23 through the control module 62 according to the fault state of the grid-connected relay control device 100 or the energy storage inverter circuit 200 when the grid-connected relay control device 100 or the energy storage inverter circuit 200 fails.

[0179] An embodiment of the present invention provides an energy storage inverter circuit 200. On the basis of the above embodiments, continue to refer to Figure 9, the energy storage inverter circuit 200 provided by the embodiment of the present invention includes: a power supply 21, a load 22, and a grid-connected relay 23. The power supply 21 is connected to the load 22 and the first end of the grid-connected relay 23 at a first node N1. The second end of the grid-connected relay 23 is connected to the power grid at a second node N2. The control end of the grid-connected relay 23 is connected to the grid-connected relay control device 100 proposed in any of the above embodiments, and / or the grid-connected relay 23 is controlled by the grid-connected relay control method proposed in any of the above embodiments, and has the beneficial effects of the grid-connected relay control device 100 and the grid-connected relay control method proposed in any of the above embodiments, which will not be elaborated here.

[0180] Note that the above is only the preferred embodiment of the present invention and the applied technical principle. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A grid-connected relay control method, characterized in that, For a grid-connected relay control device, the grid-connected relay control device is connected to the grid-connected relay of the energy storage inverter circuit. The energy storage inverter circuit includes: a power supply, a load, and a grid-connected relay. The power supply is connected to the load and the first end of the grid-connected relay at a first node, and the second end of the grid-connected relay is connected to the power grid at a second node; The grid-connected relay control method includes: Closing the grid-connected relay connected to the N phase of the second node; Obtaining a first voltage of at least one phase of the three-phase voltage of the second node; Controlling the target relay to close according to the difference between the first voltage and a preset threshold voltage; the target relay is the grid-connected relay connected to the phase line where the amplitude of the first voltage is equal to the preset threshold voltage.

2. The method according to claim 1, wherein The obtaining of the first voltage of at least one phase of the three-phase voltage of the second node includes: Obtaining the A-phase voltage of the power grid of the second node; And / or, obtaining the B-phase voltage of the power grid of the second node; And / or, obtaining the C-phase voltage of the power grid of the second node.

3. The method according to claim 1 or 2, characterized in that, The grid-connected relay includes a grid-side relay. The grid-side relay includes an A-phase grid-side relay, a B-phase grid-side relay, and a C-phase grid-side relay. The A-phase grid-side relay, the B-phase grid-side relay, and the C-phase grid-side relay are respectively connected to the phase lines of the power grid at the second node; the first voltage includes at least one of the A-phase voltage, the B-phase voltage, and the C-phase voltage; The controlling the target relay to close according to the difference between the first voltage and a preset threshold voltage includes: When the absolute value of the amplitude of the A-phase voltage is equal to the preset threshold voltage, controlling the A-phase grid-side relay to be powered on and closed; When the absolute value of the amplitude of the B-phase voltage is equal to the preset threshold voltage, controlling the B-phase grid-side relay to be powered on and closed; When the absolute value of the amplitude of the C-phase voltage is equal to the preset threshold voltage, controlling the C-phase grid-side relay to be powered on and closed; the preset threshold voltage includes 0V.

4. The method according to claim 3, wherein The grid-side relay further includes an N-phase grid-side relay, the N-phase grid-side relay; The closing of the grid-connected relay connected to the N phase of the second node includes: Closing the N-phase grid-side relay connected to the N phase of the second node.

5. The method according to claim 3, wherein The grid-connected relay further includes an inverter-side relay. The inverter-side relay includes an N-phase inverter-side relay, an A-phase inverter-side relay, a B-phase inverter-side relay, and a C-phase inverter-side relay; the N-phase inverter-side relay, the A-phase inverter-side relay, the B-phase inverter-side relay, and the C-phase inverter-side relay are respectively connected to the phase lines of the power supply and the phase lines of the load at the first node; Before closing the grid-connected relay connected to the N phase of the second node, it further includes: Connecting the N-phase inverter-side relay connected to the N phase of the first node; Connecting the A-phase inverter-side relay connected to the A phase of the first node; Connecting the B-phase inverter-side relay connected to the B phase of the first node; Connect the C-phase inverter-side relay connected to the C-phase of the first node.

6. The method according to claim 3, characterized in that, Before closing the grid-connected relay connected to the N-phase of the second node, it further includes: Determine that the grid-connected relay meets the grid connection conditions; Determine that there are no faults in the grid-connected relay control device and the energy storage inverter circuit.

7. The method according to claim 6, wherein The determination that the grid-connected relay meets the grid connection conditions includes: After the energy storage inverter circuit operates in open loop for a first preset time, perform phase-locked loop operation; When the open-loop voltage and phase of the energy storage inverter circuit are respectively the same as the voltage and phase of the power grid, it is determined that the grid-connected relay meets the grid connection conditions.

8. The method according to claim 1, wherein The grid-connected relay control device includes a first sampling control unit and a second sampling control unit. The first sampling control unit and the second sampling control unit are respectively connected to the grid-connected relay, and the first sampling control unit and the second sampling control unit are communicatively connected; The control of closing the target relay according to the difference between the first voltage and the preset threshold voltage includes: The first sampling control unit controls the closing of the target relay according to the difference between the first voltage and the preset threshold voltage; After the control of closing the target relay according to the difference between the first voltage and the preset threshold voltage, it further includes: When the first sampling control unit is in a preset working condition, the second sampling control unit maintains the closed state of the grid-connected relay; When a fault occurs in the grid-connected relay control device or the energy storage inverter circuit, the first sampling control unit or the second sampling control unit controls the grid-connected relay to power off according to the fault state of the grid-connected relay control device or the energy storage inverter circuit.

9. A grid-connected relay control device, characterized in that The grid-connected relay control device is connected to the control terminal of the grid-connected relay of the energy storage inverter circuit. The energy storage inverter circuit includes: a power source, a load, and a grid-connected relay. The power source is connected to the load and the first end of the grid-connected relay at a first node, and the second end of the grid-connected relay is connected to the power grid at a second node; The grid-connected relay control device includes: A sampling control module, connected to the second node, for obtaining at least one first voltage of the three-phase voltage of the second node; generating a control signal according to the difference between the first voltage and the preset threshold voltage; A control module, connected to the sampling control module and the control terminal of the grid-connected relay. The control module is used to control the grid-connected relay connected to the N-phase of the second node to close, and control the closing of the target relay according to the control signal; the target relay is the grid-connected relay connected to the phase line where the amplitude of the first voltage is equal to the preset threshold voltage.

10. The grid-connected relay control device according to claim 9, wherein, The grid-connected relay includes a grid-side relay. The grid-side relay includes an A-phase grid-side relay, a B-phase grid-side relay, and a C-phase grid-side relay. The A-phase grid-side relay, the B-phase grid-side relay, and the C-phase grid-side relay are respectively connected to the phase lines of the power grid at the second node; the first voltage includes at least one of the A-phase voltage, the B-phase voltage, and the C-phase voltage; The sampling control module is specifically configured to generate a first control signal when the absolute value of the amplitude of the phase-A voltage is equal to the preset threshold voltage; the control module is configured to control the energization and closing of the phase-A grid-side relay according to the first control signal; The sampling control module is configured to generate a second control signal when the absolute value of the amplitude of the phase-B voltage is equal to the preset threshold voltage; The control module is configured to control the energization and closing of the phase-B grid-side relay according to the second control signal; The sampling control module is configured to generate a third control signal when the absolute value of the amplitude of the phase-C voltage is equal to the preset threshold voltage; The control module is configured to control the energization and closing of the phase-C grid-side relay according to the third control signal; the preset threshold voltage includes 0V.

11. The grid-connected relay control device according to claim 9 or 10, characterized in that The sampling control module includes a first sampling control unit and a second sampling control unit. The first sampling control unit and the second sampling control unit are respectively connected to the grid-connected relay, and the first sampling control unit and the second sampling control unit are communicatively connected; The first sampling control unit is configured to generate a control signal according to the difference between the first voltage and the preset threshold voltage, and control the target relay to close through the control module; The second sampling control unit is configured to maintain the closed state of the grid-connected relay through the control module when the first sampling control unit is in a preset working condition; The first sampling control unit or the second sampling control unit is further configured to, when a failure occurs in the grid-connected relay control device or the energy storage inverter circuit, control the grid-connected relay to de-energize according to the failure state of the grid-connected relay control device or the energy storage inverter circuit through the control module.

12. A energy storage inverter circuit, characterized in that, Comprising: A power supply, a load, and a grid-connected relay. The power supply is connected to the load and the first end of the grid-connected relay at a first node. The second end of the grid-connected relay is connected to the grid at a second node. The control end of the grid-connected relay is connected to the grid-connected relay control device according to any one of claims 9 to 11, and / or, the grid-connected relay is controlled by the grid-connected relay control method according to any one of claims 1 to 8.

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