Energy storage system and power supply system

Abstract

An energy storage system and a power supply system, the energy storage system comprising a controller, a grid-connection switch and a power conversion system. The power conversion system comprises a power conversion circuit, a first voltage sampling circuit and a second voltage sampling circuit, an alternating current output end of the power conversion circuit being connected to a first end of the grid-connection switch by means of the first voltage sampling circuit; a second end of the grid-connection switch is used for connecting to a power grid; the second voltage sampling circuit is used for connecting to the power grid; the first voltage sampling circuit is used for sampling a converter voltage of the power conversion system; the second voltage sampling circuit is used for sampling a voltage of the power grid; when the energy storage system needs to be connected into the power grid and the converter voltage is synchronous with the voltage of the power grid, the controller is used for controlling closing of the grid-connection switch. The power conversion system can directly sample voltages of power grids, and the grid-connection switch only needs to have a simple function of being controlled, thus reducing the complexity of grid-connection switches, lowering costs, and also improving the real-time performance of grid-connection detection.

Description

Energy storage system and power supply system

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on March 28, 2023, with application number 202310321292.8 and invention name “A Energy Storage System and Power Supply System”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of power electronics technology, and in particular to an energy storage system and a power supply system. Background Art

[0003] In order to meet the grid-connected and off-grid requirements of the energy storage system, the energy storage system often sets a grid-connected switch between the power conversion system (PCS) and the power grid. When the grid-connected switch is closed, the energy storage converter is grid-connected; when the grid-connected switch is opened, the energy storage converter is off-grid.

[0004] However, when the grid-connected switch is disconnected, there's no electrical connection between the PCS and the grid. When the PCS needs to connect to the grid, the grid-connected switch must detect grid information and transmit it to the PCS via a communication link between the two. The PCS then determines the grid-connected conditions and controls the grid-connected switch, including closing it. This requires the grid-connected switch to detect grid information and maintain real-time communication with the PCS, increasing the complexity and cost of the grid-connected switch and potentially inducing communication delays.

[0005] Summary of the Invention

[0006] In view of this, the present application provides an energy storage system and a power supply system, which simplify the functions of the grid-connected switch and have low costs; the real-time performance of the grid-connected control is higher and the control effect is better.

[0007] To solve the above problems, the technical solutions provided by this application are as follows:

[0008] In a first aspect of the present application, an energy storage system is provided, comprising: a controller, a grid-connected switch, and an energy storage converter;

[0009] The energy storage converter includes: a power conversion circuit, a first voltage sampling circuit and a second voltage sampling circuit;

[0010] The AC output end of the power conversion circuit is connected to the first end of the grid-connected switch through the first voltage sampling circuit; the second end of the grid-connected switch is used to connect to the grid; the second voltage sampling circuit is used to connect to the grid;

[0011] The first voltage sampling circuit is used to sample the converter voltage of the energy storage converter;

[0012] The second voltage sampling circuit is used to sample the grid voltage;

[0013] The controller is used to control the grid-connected switch to close when the energy storage system needs to be connected to the grid and the converter voltage is synchronized with the grid voltage.

[0014] Preferably, the controller is specifically configured to adjust the converter voltage according to the grid voltage when the energy storage system needs to be connected to the grid, so that the converter voltage is synchronized with the grid voltage.

[0015] Preferably, the controller is further configured to control the converter voltage to remain within a preset voltage range when the energy storage system needs to be off-grid, increase the virtual impedance of the AC output terminal of the energy storage converter, and then control the grid-connected switch to disconnect.

[0016] Preferably, the controller is specifically used to determine that the energy storage system needs to be off-grid when the grid-connected switch is closed and the grid voltage is abnormal; and to determine that the energy storage system needs to be grid-connected when the grid-connected switch is disconnected and the grid voltage returns to normal.

[0017] Preferably, the energy storage system specifically includes a plurality of energy storage converters;

[0018] A plurality of energy storage converters are connected in parallel to a first end of a grid-connected switch;

[0019] The multiple energy storage converters include a master converter and the rest are slave converters;

[0020] The controller is the controller of the host converter.

[0021] Preferably, the power conversion circuit specifically includes: a first DC conversion circuit, a second DC conversion circuit and an inverter circuit;

[0022] The first end of the first DC conversion circuit, the first end of the second DC conversion circuit and the input end of the inverter circuit are connected together;

[0023] The second end of the first DC conversion circuit is used to connect to the photovoltaic array;

[0024] The second end of the second DC conversion circuit is used to connect to the energy storage device;

[0025] The output end of the inverter circuit is the AC output end of the power conversion circuit.

[0026] A second aspect of the present application provides a power supply system, comprising: a controller, a grid-connected switch, and an inverter;

[0027] The inverter includes: an inverter circuit, a first voltage sampling circuit and a second voltage sampling circuit;

[0028] The output end of the inverter circuit is connected to the first end of the grid-connected switch through the first voltage sampling circuit; the second end of the grid-connected switch is used to connect to the grid; the second voltage sampling circuit is used to connect to the grid;

[0029] The first voltage sampling circuit is used for sampling the inverter voltage of the inverter;

[0030] The second voltage sampling circuit is used to sample the grid voltage;

[0031] The controller is used to control the grid-connected switch to close when the power system needs to be connected to the grid and the inverter voltage is synchronized with the grid voltage.

[0032] Preferably, the controller is specifically configured to adjust the inverter voltage according to the grid voltage when the power supply system needs to be connected to the grid, so that the inverter voltage is synchronized with the grid voltage.

[0033] Preferably, the controller is further configured to control the inverter voltage to remain within a preset voltage range, increase the virtual impedance at the output end of the inverter, and then control the grid-connected switch to disconnect when the power system needs to be disconnected from the grid.

[0034] Preferably, the controller is specifically used to determine that the power system needs to be off-grid when the grid-connected switch is closed and the grid voltage is abnormal; and to determine that the power system needs to be grid-connected when the grid-connected switch is disconnected and the grid voltage returns to normal.

[0035] It can be seen that this application has the following beneficial effects:

[0036] The energy storage system provided herein includes: a controller, a grid-connected switch, and an energy storage converter. The energy storage converter includes: a power conversion circuit, a first voltage sampling circuit, and a second voltage sampling circuit. The AC output end of the power conversion circuit is connected to the first end of the grid-connected switch via the first voltage sampling circuit. The second end of the grid-connected switch is connected to the grid. The second voltage sampling circuit is connected to the grid. The first voltage sampling circuit is used to sample the converter voltage of the energy storage converter; the second voltage sampling circuit is used to sample the grid voltage. The controller is used to control the grid-connected switch to close when the converter voltage is synchronized with the grid voltage. Regardless of whether the grid-connected switch is closed or not, the second voltage sampling circuit remains electrically connected to the grid and can sample the grid voltage. Because the second voltage sampling circuit is a functional circuit within the energy storage converter, the energy storage converter can directly obtain the grid voltage sampled by the second voltage sampling circuit, eliminating the communication connection required for this part of data transmission and improving real-time performance. In the energy storage system provided herein, the energy storage converter can directly sample the grid voltage, and the grid-connected switch only needs to have a simple control function. This simplifies the complexity of the grid-connected switch, reduces costs, and improves the real-time performance of grid connection detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG1 is a schematic diagram of an energy storage system;

[0038] FIG2 is a schematic diagram of an energy storage system provided in an embodiment of the present application;

[0039] FIG3 is a schematic diagram of another energy storage system provided in an embodiment of the present application;

[0040] FIG4 is a schematic diagram of a power supply system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand and implement the technical solution of this application, the specific application scenarios of this application are introduced below.

[0042] Refer to Figure 1, which is a schematic diagram of an energy storage system.

[0043] The energy storage system includes: grid-connected switch K1 and energy storage converter PCS.

[0044] The AC output end of the energy storage converter PCS is connected to a first end of the grid-connected switch K1 ; the second end of the grid-connected switch K1 is connected to the power grid.

[0045] The second end of the grid-connected switch K1 is further provided with a sampling port for sampling the voltage of the grid; and there is also a communication connection between the grid-connected switch K1 and the PCS.

[0046] When the energy storage system needs to be connected to the grid, the sampling port of the grid-connected switch K1 samples the grid voltage and transmits it to the PCS through the communication connection; the PCS completes the sampling of the voltage at its own output end; the PCS compares the grid voltage with the voltage at the PCS output end, and when the grid-connected conditions are met, the grid-connected switch K1 is controlled to close.

[0047] It can be seen that in the energy storage system shown in Figure 1, the grid-connected switch needs to have a sampling function and needs to add corresponding communication connections, which makes the implementation more complicated; and the control is based on the information obtained through communication, which results in a high delay.

[0048] The embodiments of the present application are described in detail below with reference to the accompanying drawings and specific implementation methods.

[0049] See Figure 2, which is a schematic diagram of an energy storage system provided in an embodiment of the present application.

[0050] The energy storage system provided in the embodiment of the present application includes: a controller (not shown in the figure), a grid-connected switch K2 and an energy storage converter PCS.

[0051] The energy storage converter PCS includes a first voltage sampling circuit 100 , a second voltage sampling circuit 200 and a power conversion circuit 300 .

[0052] The AC output terminal of the power conversion circuit 300 is connected to the first terminal of the grid-connected switch K2 through the first voltage sampling circuit 100 .

[0053] The second end of the grid-connected switch K2 is used to connect to the grid.

[0054] The second voltage sampling circuit 200 is also used to connect to the power grid.

[0055] The first end of the grid-connected switch K2 is also used to connect to a load.

[0056] It should be understood that Figure 2 is only one possible implementation method, which reflects the difference between the energy storage system being connected to the grid and being connected to the load; in other possible implementation methods, the first end of the grid-connected switch K2 may also not be connected to the load, and the energy storage system only exchanges energy with the grid.

[0057] The first voltage sampling circuit 100 is used to sample the converter voltage of the energy storage converter.

[0058] The second voltage sampling circuit 200 is used to sample the grid voltage.

[0059] Regardless of whether the grid-connected switch K2 is closed or open, the second voltage sampling circuit 200 is connected to the grid and can sample the grid voltage. Moreover, the second voltage sampling circuit 200 is a functional circuit inside the PCS, and the grid voltage sampled by it does not need to be transmitted to the PCS through a communication connection, which reduces the communication delay to a certain extent.

[0060] The controller is used to control the grid-connected switch to close when the converter voltage is synchronized with the grid voltage.

[0061] The synchronization of the converter voltage and the grid voltage specifically means that the frequency, phase and amplitude of the converter voltage and the grid voltage are consistent. The consistency of the frequency, phase and amplitude of the converter voltage and the grid voltage can reduce the impact of the energy storage system on the grid when it is connected to the grid, thereby improving the stability of the grid.

[0062] It should be understood that the frequency, phase and amplitude of the converter voltage are consistent with those of the grid voltage, but are not strictly required to be equal, and a certain error range is allowed.

[0063] In some possible embodiments, in order to synchronize the converter voltage with the grid voltage, the controller may specifically adjust the converter voltage according to the grid voltage.

[0064] The energy storage system provided by the embodiment of the present application includes: a controller, a grid-connected switch and an energy storage converter; the energy storage converter includes: a power conversion circuit, a first voltage sampling circuit and a second voltage sampling circuit; the AC output end of the power conversion circuit is connected to the first end of the grid-connected switch through the first voltage sampling circuit; the second end of the grid-connected switch is used to connect to the power grid; the second voltage sampling circuit is used to connect to the power grid. The first voltage sampling circuit is used to sample the converter voltage of the energy storage converter; the second voltage sampling circuit is used to sample the power grid voltage; the controller is used to control the grid-connected switch to close when the converter voltage is synchronized with the power grid voltage. Regardless of whether the grid-connected switch is closed or not, the second voltage sampling circuit maintains an electrical connection with the power grid and can sample the power grid voltage; since the second voltage sampling circuit is a functional circuit inside the energy storage converter, the energy storage converter can directly obtain the power grid voltage sampled by the second voltage sampling circuit, eliminating the communication connection required for this part of data transmission, and having better real-time performance. In the energy storage system provided in the embodiment of the present application, the energy storage converter can directly sample the grid voltage, and the grid-connected switch only needs to have a simple controlled function; this simplifies the complexity of the grid-connected switch, reduces costs, and improves the real-time performance of grid-connected detection.

[0065] In some embodiments, to increase the available power of the energy storage system, the energy storage system may use multiple energy storage converters connected in parallel, as described in detail below with reference to the accompanying drawings.

[0066] See FIG3 , which is a schematic diagram of another energy storage system provided in an embodiment of the present application.

[0067] Similar to the above embodiment, the energy storage system provided in the embodiment of the present application includes: a controller, a grid-connected switch K2 and an energy storage converter.

[0068] The energy storage system specifically includes a plurality of energy storage converters, namely a first energy storage converter PCS1 to an nth energy storage converter PCSn, wherein n≥2, and n is an integer.

[0069] A plurality of energy storage converters are connected in parallel to the first end of the grid-connected switch K2.

[0070] The remaining connection relationships between the grid-connected switch K2 and the energy storage converter can refer to the above embodiment and will not be repeated here.

[0071] In order to ensure the accuracy of the first voltage sampling circuit and the second voltage sampling circuit, the present application uses multiple identical PCSs and connects the second voltage sampling circuit in each PCS to the power grid. In this case, the first voltage sampling circuits of multiple PCSs can verify the accuracy of the sampling results with each other, and the same applies to the second voltage sampling circuits. This improves the accuracy of grid connection detection.

[0072] Of course, after the PCSs are connected in parallel, the converter voltages sampled by the first voltage sampling circuits of different PCSs should be consistent, and the grid voltages sampled by the second voltage sampling circuits should also be consistent; therefore, in order to simplify the connection relationship of the energy storage system, only the second voltage sampling circuit in one PCS can be used to connect to the grid; even in order to reduce the total cost of the PCS, only one PCS can have the first voltage sampling circuit and the second voltage sampling circuit, and the other PCSs do not have the first voltage sampling circuit and the second voltage sampling circuit.

[0073] This application does not specifically limit the specific application scenarios of the energy storage system. For example, the energy storage system is often combined with new energy power generation equipment to perform control such as smoothing the fluctuations of new energy power generation, so that the power grid can better absorb the electricity provided by the new energy power generation equipment.

[0074] The embodiments of the present application are described in detail using an energy storage system combined with a photovoltaic array for grid connection as an example.

[0075] Specifically, the power conversion circuit 300 includes: a first DC conversion circuit DCDC1 , a second DC conversion circuit DCDC2 , and an inverter circuit DCAC.

[0076] A first end of the first DC conversion circuit DCDC1 , a first end of the second DC conversion circuit DCDC2 , and an input end of the inverter circuit DCAC are connected together.

[0077] The second end of the first DC conversion circuit DCDC1 is used to connect to the photovoltaic array.

[0078] The second end of the second DC conversion circuit DCDC2 is used to connect to the energy storage device.

[0079] The output end of the inverter circuit DCAC is the AC output end of the energy storage converter.

[0080] To facilitate control of multiple energy storage converters, one possible implementation employs a master-slave control scheme, with master and slave controllers configured within the multiple energy storage converters. The controller controlling the grid-connected switch is specifically the controller of the master converter. Of course, in other possible implementations, a single master controller can control each PCS separately, a practice not specifically limited in this application.

[0081] For example, in the embodiment of the present application, the first energy storage converter PCS1 is the master, and the remaining energy storage converters are slaves.

[0082] When the energy storage system switches from grid-connected to off-grid:

[0083] It should be understood that in the grid-connected state, the voltages sampled by the first voltage sampling circuit and the second voltage sampling circuit are the same. If any voltage detection circuit of the host converter detects an abnormal grid voltage, or if the slave converter detects an abnormal grid voltage, the host is informed through the communication connection between the master and slave machines, causing the host controller to take action.

[0084] The host controller is specifically used to control the converter voltage to maintain within a preset voltage range, increase the virtual impedance of the AC output end of the energy storage converter, and then control the grid-connected switch K2 to disconnect.

[0085] Controlling the converter voltage to maintain within the preset voltage range can prevent abnormal grid voltage from causing abnormal voltage in the energy storage converter and improve the stability of the energy storage system operation.

[0086] Increasing the virtual impedance of the AC output end of the energy storage converter can prevent overcurrent and ensure the safety of the energy storage system.

[0087] When the energy storage system switches from off-grid to grid-connected:

[0088] When the host controller detects that the grid voltage of the second voltage sampling circuit returns to normal, it adjusts the converter voltage according to the grid voltage. When the converter voltage is synchronized with the grid voltage, it controls the grid-connected switch K2 to close.

[0089] Specifically, the master converter may inform the slave converter via a communication connection with the slave converter, and the controller of the slave converter and the controller of the master converter jointly control the synchronization of the converter voltages.

[0090] It should be understood that when the energy storage system needs to be connected to the grid or disconnected from the grid, in addition to the automatic detection of whether the voltage is abnormal in the above embodiment, a manual grid connection instruction may also be issued; this application does not make specific limitations on this.

[0091] Based on the energy storage system provided in the above embodiments, the present application also provides a power supply system, which is described in detail below with reference to the accompanying drawings.

[0092] In addition to energy storage scenarios, the solutions provided in the above embodiments can also be further applied to power supply systems with multiple inverters connected in parallel.

[0093] The present application does not specifically limit the application scenario of the power supply system. For example, the power supply system may be a grid-connected system of a photovoltaic array; or a grid-connected system of a wind turbine generator set.

[0094] See Figure 4, which is a schematic diagram of a power supply system provided in an embodiment of the present application.

[0095] As shown in FIG4 , the power supply system provided in the embodiment of the present application includes: a grid-connected switch K3 and an inverter DCAC.

[0096] The inverter DCAC includes an inverter circuit 400 , a first voltage sampling circuit 100 and a second voltage sampling circuit 200 .

[0097] The output end of the inverter circuit 400 is connected to the first end of the grid-connected switch K3 through the first voltage sampling circuit 100 .

[0098] The second end of the grid-connected switch K3 is used to connect to the grid. The second voltage sampling circuit 200 is used to connect to the grid.

[0099] The first voltage sampling circuit 100 is used to sample the inverter voltage of the inverter. The second voltage sampling circuit 200 is used to sample the grid voltage.

[0100] Regardless of whether the grid-connected switch K3 is closed or open, the second voltage sampling circuit 200 is connected to the grid and can sample the grid voltage. Moreover, the second voltage sampling circuit 200 is a functional circuit inside the inverter, and the grid voltage sampled by it does not need to be transmitted to the inverter through a communication connection, which reduces the communication delay to a certain extent.

[0101] The controller is used to control the grid-connected switch to close when the power system needs to be connected to the grid and the inverter voltage is synchronized with the grid voltage.

[0102] In some embodiments, the controller is specifically configured to adjust the inverter voltage according to the grid voltage so as to synchronize the inverter voltage with the grid voltage to control the grid-connected switch to close.

[0103] In some embodiments, the controller is specifically used to determine that the power system needs to be off-grid when the grid-connected switch is closed and the grid voltage is abnormal; and to determine that the power system needs to be connected to the grid when the grid-connected switch is disconnected and the grid voltage returns to normal.

[0104] It should be understood that the control of the power system being connected to or disconnected from the grid can also be completed by manually issuing a grid connection instruction or a grid disconnection instruction, and this application does not make specific limitations on this.

[0105] In some embodiments, the controller is specifically used to control the inverter voltage to maintain within a preset voltage range, increase the virtual impedance of the inverter output end, and then control the grid-connected switch to disconnect when the power system needs to be off-grid.

[0106] Controlling the inverter voltage to maintain within the preset voltage range before leaving the grid can prevent abnormal grid voltage and other situations from having a significant impact on the voltage of the power supply system; and improve the stability of the power supply system.

[0107] Increasing the virtual impedance at the output of the inverter can avoid transient overcurrent when the grid-connected switch is disconnected, thereby improving the safety of the power supply system.

[0108] The power supply system provided by the present application includes: a controller, a grid-connected switch, and an inverter; the inverter includes: an inverter circuit, a first voltage sampling circuit, and a second voltage sampling circuit; the output end of the inverter circuit is connected to the first end of the grid-connected switch via the first voltage sampling circuit; the second end of the grid-connected switch is connected to the grid; and the second voltage sampling circuit is connected to the grid. The first voltage sampling circuit is used to sample the inverter voltage of the inverter; the second voltage sampling circuit is used to sample the grid voltage; and the controller is used to control the grid-connected switch to close when the inverter voltage is synchronized with the grid voltage. Regardless of whether the grid-connected switch is closed or not, the second voltage sampling circuit remains electrically connected to the grid and can sample the grid voltage. Because the second voltage sampling circuit is a functional circuit within the inverter, the inverter can directly obtain the grid voltage sampled by the second voltage sampling circuit, eliminating the communication connection required for this part of the data transmission and improving real-time performance. The power supply system provided by the present application enables the inverter to directly sample the grid voltage, and the grid-connected switch only needs to have a simple control function. This simplifies the complexity of the grid-connected switch, reduces costs, and improves the real-time performance of grid-connected detection.

[0109] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referenced to each other.

[0110] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An energy storage system, characterized in that: include: Controllers, grid-connected switches and energy storage converters; The energy storage converter comprises: a power conversion circuit, a first voltage sampling circuit and a second voltage sampling circuit; The AC output end of the power conversion circuit is connected to the first end of the grid-connected switch through the first voltage sampling circuit; the second end of the grid-connected switch is used to connect to the grid; the second voltage sampling circuit is used to connect to the grid; The first voltage sampling circuit is used to sample the converter voltage of the energy storage converter; The second voltage sampling circuit is used to sample the grid voltage; The controller is used to control the grid-connected switch to close when the energy storage system needs to be grid-connected and the converter voltage is synchronized with the grid voltage.

2. The energy storage system according to claim 1, characterized in that The controller is specifically configured to adjust the converter voltage according to the grid voltage when the energy storage system needs to be connected to the grid, so that the converter voltage is synchronized with the grid voltage.

3. The energy storage system according to claim 2, characterized in that: The controller is also used to control the converter voltage to maintain within a preset voltage range when the energy storage system needs to be off-grid, increase the virtual impedance of the AC output end of the energy storage converter, and then control the grid-connected switch to disconnect.

4. The energy storage system according to claim 3, characterized in that The controller is specifically used to determine that the energy storage system needs to be disconnected from the grid when the grid-connected switch is closed and the grid voltage is abnormal; and to determine that the energy storage system needs to be connected to the grid when the grid-connected switch is disconnected and the grid voltage returns to normal.

5. The energy storage system according to any one of claims 1 to 4, characterized in that: The energy storage system specifically includes a plurality of energy storage converters; The multiple energy storage converters are connected in parallel to the first end of the grid-connected switch; The multiple energy storage converters include a master converter, and the rest are slave converters; The controller is a controller of the host converter.

6. The energy storage system according to any one of claims 1 to 4, characterized in that: The power conversion circuit specifically includes: a first DC conversion circuit, a second DC conversion circuit and an inverter circuit; The first end of the first DC conversion circuit, the first end of the second DC conversion circuit and the input end of the inverter circuit are connected together; The second end of the first DC conversion circuit is used to connect to a photovoltaic array; The second end of the second DC conversion circuit is used to connect to the energy storage device; The output end of the inverter circuit is the AC output end of the power conversion circuit.

7. A power supply system, characterized in that: include: Controllers, grid-connected switches and inverters; The inverter includes: an inverter circuit, a first voltage sampling circuit and a second voltage sampling circuit; The output end of the inverter circuit is connected to the first end of the grid-connected switch through the first voltage sampling circuit; the second end of the grid-connected switch is used to connect to the grid; the second voltage sampling circuit is used to connect to the grid; The first voltage sampling circuit is used to sample the inverter voltage of the inverter; The second voltage sampling circuit is used to sample the grid voltage; The controller is used to control the grid-connected switch to close when the power supply system needs to be grid-connected and the inverter voltage is synchronized with the grid voltage.

8. The power supply system according to claim 7, characterized in that: The controller is specifically configured to adjust the inverter voltage according to the grid voltage when the power supply system needs to be connected to the grid, so that the inverter voltage is synchronized with the grid voltage.

9. The power supply system according to claim 8, characterized in that: The controller is further configured to control the inverter voltage to remain within a preset voltage range, increase the virtual impedance of the inverter output end, and then control the grid-connected switch to disconnect when the power supply system needs to be disconnected from the grid.

10. The power supply system according to claim 9, characterized in that: The controller is specifically used to determine that the power supply system needs to be disconnected from the grid when the grid-connected switch is closed and the grid voltage is abnormal; and to determine that the power supply system needs to be connected to the grid when the grid-connected switch is disconnected and the grid voltage returns to normal.

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