UPS load-based photovoltaic and storage integrated inverter on-grid and off-grid switching circuit and method

Abstract

A UPS-based on-grid and off-grid switching circuit and method for a photovoltaic-storage integrated inverter includes a first relay and a third relay connected in series between the photovoltaic-storage integrated inverter and the grid's live wire L, while a second relay and a fourth relay are connected in series between the photovoltaic-storage integrated inverter and the grid's neutral wire N. A fifth relay is connected downstream of the third relay between the grid's live wire L and the UPS load's live wire L1. A sixth relay is connected downstream of the fourth relay between the grid's neutral wire N and the UPS load's neutral wire N1. A first bidirectional thyristor is connected in parallel between the grid's live wire L and the UPS load's live wire L1, while a second bidirectional thyristor is connected in parallel between the grid's neutral wire N and the UPS load's neutral wire N1. The photovoltaic-storage integrated inverter is connected to the UPS load's live wire L1 via a first switch and to the UPS load's neutral wire N1 via a second switch. The UPS load remains powered on during mode switching, and the number of relay closures in each mode is minimal, resulting in low relay drive losses.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic energy storage power generation and power supply, and in particular to a photovoltaic energy storage integrated inverter on-grid and off-grid switching circuit based on a UPS load. Background Art

[0002] The patent application with application number 2019105101726 constructs the grid-connected and off-grid switching circuit of the energy storage inverter through 9 relays, which can realize arbitrary switching between grid-connected, off-grid and bypass modes between the energy storage inverter, the power grid and the load.

[0003] The patent application with application number 2019110984936 constructs a grid-connected and off-grid switching circuit for a photovoltaic inverter through 8 relays, which can realize arbitrary switching between grid-connected, off-grid and bypass modes between the photovoltaic inverter, the power grid and the load.

[0004] In patent application number 2019105101726, when the switching circuit switches between on-grid and off-grid modes, six of the relays and three of the other relays need to be opened or closed in opposite directions. During this process, some relays open and others close simultaneously. Because the closing time of the relays is longer than the opening time, the load is actually in a power-off state during the on-grid and off-grid switching time. Typically, the relay closing time takes approximately 10ms or more, and the closing time of the relay contacts will increase with the passage of time. Therefore, during the on-grid and off-grid switching process, the power-off time of the load in this circuit will be greater than 10ms. Similarly, when the switching circuit switches between off-grid and bypass modes, three of the relays and four of the other relays need to be opened or closed in opposite directions. Some relays open and others close simultaneously. Therefore, during the off-grid and bypass switching process, the power-off time of the load in this circuit will also be greater than 10ms.

[0005] In the patent application with application number 2019110984936, when the switching circuit switches between on-grid and off-grid modes, it is only necessary to disconnect 4 of the 8 closed relays. Therefore, during the on-grid and off-grid switching process, the power-off time of the load is only affected by the relay disconnection time and can be controlled within 10ms. However, when the switching circuit switches between off-grid and bypass modes, 4 of the relays and the other 4 relays need to be opened or closed in opposite directions. The two operations of disconnecting some relays and closing another part of the relays will also occur at the same time. Therefore, during the off-grid and bypass switching process, the power-off time of the load will also be greater than 10ms.

[0006] Uninterruptible power supply (UPS) is mainly used to provide uninterruptible power supply to some load equipment with high requirements on power supply stability. Such loads require that the power-off time cannot exceed 10ms. Therefore, the above two switching circuits cannot fully meet the requirement that the UPS load power-off time is less than 10ms when switching between the three modes of grid connection, off-grid and bypass.

[0007] In addition, the switching circuit with application number 2019105101726 has 3 relays closed in off-grid mode and 4 relays closed in bypass mode; the switching circuit with application number 2019110984936 has 4 relays closed regardless of off-grid or bypass mode. Both switching circuits have a large number of relays in the closed state in off-grid and bypass modes, which will result in higher relay drive losses in the entire circuit. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a UPS-based on-grid and off-grid switching circuit for a photovoltaic-storage integrated inverter. When switching between on-grid, off-grid, and bypass modes, the circuit can meet the UPS load power-off time control requirements. Furthermore, in off-grid and bypass modes, the number of relays in the closed state is relatively small, resulting in relatively low relay drive losses in the entire switching circuit.

[0009] The present invention is achieved through the following technical solutions:

[0010] The photovoltaic and storage integrated inverter on-grid and off-grid switching circuit based on UPS load is characterized by:

[0011] The first relay and the third relay are connected in series between the solar-storage integrated inverter and the live line L of the grid, and the second relay and the fourth relay are connected in series between the solar-storage integrated inverter and the neutral line N of the grid;

[0012] One end of the fifth relay is connected between the third relay and the live wire L of the grid, and the other end is connected to the live wire L1 of the UPS load; one end of the sixth relay is connected between the fourth relay and the neutral wire N of the grid, and the other end is connected to the neutral wire N1 of the UPS load;

[0013] The first bidirectional thyristor is connected in parallel between the live wire L of the grid and the live wire L1 of the UPS load, and the second bidirectional thyristor is connected in parallel between the neutral wire N of the grid and the neutral wire N1 of the UPS load;

[0014] The photovoltaic-storage integrated inverter is connected to the live wire L1 of the UPS load through the first switch and to the neutral wire N1 of the UPS load through the second switch.

[0015] Furthermore, in this switching circuit, the first switch and the second switch remain in a closed state when connected to or disconnected from the grid, and are only disconnected when in bypass mode. In actual applications, bypass conditions are indeed rare, and bypass mode is only entered when a problem occurs with the inverter module and the inverter module cannot be used. Therefore, in this switching circuit, the first switch and the second switch will not frequently switch between closed and open operations. Unlike other switching circuits, it is not necessary to configure an automatic control relay. It can also be an automatic control switch, a manual control switch (such as a push-button type, a hand brake type, a pull-cord type, etc.), an automatic control relay, or other electrical switch components.

[0016] Furthermore, the switching circuit has three modes: grid-connected, off-grid and bypass, wherein:

[0017] In the grid-connected mode, the first relay, the second relay, the third relay, the fourth relay, the fifth relay, the sixth relay, the first switch, and the second switch remain in a closed state;

[0018] In off-grid mode, the first switch and the second switch remain in a closed state, and the first relay, the second relay, the third relay, the fourth relay, the fifth relay, and the sixth relay remain in an open state;

[0019] In the bypass mode, the fifth relay and the sixth relay remain in the closed state, and the first relay, the second relay, the third relay, the fourth relay, the first switch, and the second switch remain in the open state.

[0020] The grid-connected and off-grid switching method of the above-mentioned photovoltaic storage integrated inverter grid-connected and off-grid switching circuit based on UPS load is as follows:

[0021] When switching from grid-connected to off-grid, the first relay, the second relay, the third relay, the fourth relay, the fifth relay, and the sixth relay are disconnected, the first switch and the second switch are always kept closed, and the photovoltaic and energy storage integrated inverter works off-grid;

[0022] When switching from off-grid to grid-connected, the first relay, the second relay, the third relay, the fourth relay, the fifth relay, and the sixth relay are closed, the first switch and the second switch are always kept closed, and the photovoltaic and energy storage integrated inverter works in grid connection.

[0023] The grid-connected and bypass switching method of the above-mentioned photovoltaic storage integrated inverter on-grid and off-grid switching circuit based on UPS load is applied:

[0024] When the grid is switched to bypass, the first relay, second relay, third relay, fourth relay, first switch and second switch are disconnected, while the fifth relay and sixth relay remain closed, and the UPS load is powered by the grid.

[0025] When the bypass is switched to grid connection, the first switch and the second switch of the first relay, the second relay, the third relay, and the fourth relay are closed, and the fifth relay and the sixth relay are always kept closed, and the photovoltaic storage integrated inverter works in grid connection.

[0026] The off-grid and bypass switching method of the above-mentioned photovoltaic storage integrated inverter and off-grid switching circuit based on UPS load is applied:

[0027] When the off-grid mode is switched to bypass mode, the first bidirectional thyristor and the second bidirectional thyristor are turned on first. After the fifth relay and the sixth relay are closed, the first bidirectional thyristor and the second bidirectional thyristor are turned off again, and the UPS load is powered by the grid.

[0028] When the bypass is switched to off-grid, the first bidirectional thyristor and the second bidirectional thyristor are turned on first. After the first switch and the second switch are closed, the first bidirectional thyristor and the second bidirectional thyristor are turned off again, and the photovoltaic and energy storage integrated inverter works off-grid.

[0029] The present switching circuit and switching method, during the on-grid and off-grid switching process, since the first switch and the second switch are in a normally closed state and are never disconnected, only the first breaker to the sixth relay are opened or closed, thus ensuring that the UPS load is continuously supplied with power during this process and the UPS load will not be powered off; during the on-grid and off-bypass switching process, since the fifth relay and the sixth relay are in a normally closed state and are never disconnected, only the first breaker to the fourth relay, the first switch and the second switch are opened or closed, thus ensuring that the UPS load is continuously supplied with power during this process and the UPS load will not be powered off; during the off-grid and off-bypass switching process, The first bidirectional thyristor and the second bidirectional thyristor first establish a temporary power supply path between the power grid and the UPS load, and then perform the opening and closing operations of the fifth relay, the sixth relay, the first switch and the second switch, and wait until the closing action is completed and the UPS load power supply circuit is connected before disconnecting the temporary power supply path. Therefore, it can also ensure that the UPS load is continuously powered during this process, and the UPS load will not be powered off. Under the premise of ensuring continuous power supply to the UPS load without interruption in any switching of the three modes, this switching circuit has advantages over the existing switching circuit in terms of the number of operating relays and the operation type of the relay during the switching process.

[0030] Furthermore, the other end of the sixth relay is connected to the neutral line N1 of the UPS load through the seventh relay; the switching circuit has three modes: grid-connected, grid-off, and bypass, wherein: in the grid-connected mode, the first relay, the second relay, the third relay, the fourth relay, the fifth relay, the sixth relay, the seventh relay, the first switch, and the second switch remain in a closed state; in the grid-off mode, the first switch and the second switch remain in a closed state, and the first relay, the second relay, the third relay, the fourth relay, the fifth relay, the sixth relay, and the seventh relay remain in an open state; in the bypass mode, the fifth relay, the sixth relay, and the seventh relay remain in a closed state, and the first relay, the second relay, the third relay, the fourth relay, the first switch, and the second switch remain in an open state. Connecting the seventh relay in series after the sixth relay is for the purpose of redundancy design, to avoid the situation where the fifth and sixth relays are stuck at the same time when the photovoltaic storage integrated inverter is off-grid and cannot be disconnected in time (although such situations rarely occur).

[0031] The grid-connected and off-grid switching method of the above-mentioned photovoltaic storage integrated inverter grid-connected and off-grid switching circuit based on UPS load is as follows:

[0032] When switching from grid-connected to off-grid, the first relay, second relay, third relay, fourth relay, fifth relay, sixth relay, and seventh relay are disconnected, and the first switch and second switch are always kept closed, and the photovoltaic and energy storage integrated inverter works off-grid;

[0033] When switching from off-grid to grid-connected, the first relay, the second relay, the third relay, the fourth relay, the fifth relay, the sixth relay, and the seventh relay are closed, the first switch and the second switch are always kept closed, and the photovoltaic and energy storage integrated inverter works in grid connection.

[0034] The grid-connected and bypass switching method of the above-mentioned photovoltaic storage integrated inverter on-grid and off-grid switching circuit based on UPS load is applied:

[0035] When the grid is switched to bypass, the first relay, second relay, third relay, fourth relay, first switch and second switch are disconnected, while the fifth relay, sixth relay and seventh relay remain closed, and the UPS load is powered by the grid.

[0036] When the bypass is switched to grid connection, the first relay, the second relay, the third relay, the fourth relay, the first switch, and the second switch are closed, and the fifth relay, the sixth relay, and the seventh relay remain closed at all times, and the photovoltaic and energy storage integrated inverter is grid-connected.

[0037] The off-grid and bypass switching method of the above-mentioned photovoltaic storage integrated inverter and off-grid switching circuit based on UPS load is applied:

[0038] When the off-grid mode is switched to bypass mode, the first bidirectional thyristor and the second bidirectional thyristor are turned on first. After the fifth relay, the sixth relay and the seventh relay are closed, the first bidirectional thyristor and the second bidirectional thyristor are turned off again, and the UPS load is powered by the grid.

[0039] When the bypass is switched to off-grid, the first bidirectional thyristor and the second bidirectional thyristor are turned on first. After the first switch and the second switch are closed, the first bidirectional thyristor and the second bidirectional thyristor are turned off again, and the photovoltaic and energy storage integrated inverter works off-grid.

[0040] The beneficial effects of the present invention are:

[0041] 1. During any switching process between the three modes of grid connection, off-grid connection and bypass, the present switching circuit and method can ensure continuous power supply to the UPS load, and the UPS load will not experience power outages;

[0042] 2. Under the premise of ensuring that the UPS load is not disconnected during the switching process of each mode, the switching circuit and method have only two relays in the closed state at most in the off-grid mode, which is less than the 3-4 relays closed in the existing switching circuit. In fact, when the first switch and the second switch use ordinary control switches, the number of relays in the closed state is zero, and the relay drive loss of the entire switching circuit is significantly lower;

[0043] 3. Under the premise of ensuring that the UPS load is not disconnected during the switching process of each mode, the switching circuit and method have at least two relays in the closed state in the bypass mode, which is less than the four closed relays in the existing switching circuit. The smaller the number of relays in the closed state, the lower the relay drive loss of the entire switching circuit.

[0044] 4. Under the premise of ensuring that the UPS load is not disconnected during the switching process of each mode, this switching circuit and method has at least 6 relays in the closed state in the grid-connected mode, which is the same as the minimum number of 6 relays closed in the existing switching circuit, without adding any additional relay drive loss to the entire switching circuit;

[0045] 5. In this switching circuit and method, the first switch and the second switch can use ordinary control switches or even manual switches instead of remote control relays, reducing the configuration and operating costs of the entire circuit and reducing relay drive losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a circuit connection diagram of the first embodiment of the switching circuit

[0047] Figure 2 This is a circuit connection diagram of the second embodiment of the switching circuit

[0048] Figures 1-2In the figure: 1 is the first relay, 2 is the second relay, 3 is the third relay, 4 is the fourth relay, 5 is the fifth relay, 6 is the sixth relay, 7 is the first switch, 8 is the second switch, 9 is the first bidirectional thyristor, 10 is the second bidirectional thyristor, 11 is the photovoltaic and energy storage integrated inverter, 12 is the power grid, 13 is the UPS load, and 14 is the seventh relay. DETAILED DESCRIPTION

[0049] The present invention will be further described below with reference to the accompanying drawings.

[0050] exist Figure 1 、 Figure 2 In the embodiment shown, the photovoltaic panels PV1 and PV2 in the photovoltaic power generation and energy storage module are connected to the photovoltaic storage integrated inverter 11 through boost converters, and the battery is connected to the photovoltaic storage integrated inverter 11 through a bidirectional converter Buck / boost.

[0051] Example 1

[0052] exist Figure 1 In the grid-connected and off-grid switching circuit of the photovoltaic-storage integrated inverter shown, the first relay 1 and the third relay 3 are connected in series between the photovoltaic-storage integrated inverter 11 and the live wire L of the grid 12, and the second relay 2 and the fourth relay 4 are connected in series between the photovoltaic-storage integrated inverter 11 and the neutral wire N of the grid 12; one end of the fifth relay 5 is connected between the third relay 3 and the live wire L of the grid 12, and the other end is connected to the live wire L1 of the UPS load 13; one end of the sixth relay 6 is connected between the fourth relay 4 and the neutral wire N of the grid 12, and the other end is connected to the live wire L1 of the UPS load 13 Neutral line N1; the first bidirectional thyristor 9 is connected in parallel between the live line L of the power grid 12 and the live line L1 of the UPS load 13, and the second bidirectional thyristor 10 is connected in parallel between the neutral line N of the power grid 12 and the neutral line N1 of the UPS load 13; the photovoltaic and storage integrated inverter 11 is connected to the live line L1 of the UPS load 13 through the first switch 7, and is connected to the neutral line N1 of the UPS load 13 through the second switch 8. The first switch 7 and / or the second switch 8 can be any one of an automatic control switch, a manual control switch, an automatic control relay or a manual control relay.

[0053] The switching circuit has three modes: grid-connected, off-grid and bypass.

[0054] In the grid-connected mode, the first relay 1, the second relay 2, the third relay 3, the fourth relay 4, the fifth relay 5, the sixth relay 6, the first switch 7, and the second switch 8 remain in the closed state, and the photovoltaic-storage integrated inverter 11 works in grid connection;

[0055] In off-grid mode, the first switch 7 and the second switch 8 remain closed, the first relay 1, the second relay 2, the third relay 3, the fourth relay 4, the fifth relay 5, and the sixth relay 6 remain open, and the photovoltaic-storage integrated inverter 11 operates off-grid;

[0056] In bypass mode, the fifth relay 5 and the sixth relay 6 remain closed, the first relay 1, the second relay 2, the third relay 3, the fourth relay 4, the first switch 7, and the second switch 8 remain open, and the power grid 12 supplies power to the UPS load 13.

[0057] The grid-connected and off-grid switching methods of this switching circuit are as follows:

[0058] When the grid-connected state is switched to the off-grid state, the first relay 1, the second relay 2, the third relay 3, the fourth relay 4, the fifth relay 5, and the sixth relay 6 are disconnected, and the first switch 7 and the second switch 8 are always kept closed;

[0059] When switching from off-grid to grid-connected, the first relay 1, the second relay 2, the third relay 3, the fourth relay 4, the fifth relay 5, and the sixth relay 6 are closed, and the first switch 7 and the second switch 8 are always kept closed.

[0060] The grid-connected and bypass switching methods of this switching circuit are as follows:

[0061] When the grid is switched to bypass, the first relay 1, the second relay 2, the third relay 3, the fourth relay 4, the first switch 7, and the second switch 8 are disconnected, and the fifth relay 5 and the sixth relay 6 remain closed.

[0062] When the bypass is switched to grid connection, the first relay 1, the second relay 2, the third relay 3, the first switch 7 and the second switch 8 of the fourth relay 4 are closed, and the fifth relay 5 and the sixth relay 6 are always kept closed.

[0063] Off-grid and bypass switching methods of this switching circuit:

[0064] When the off-grid mode is switched to bypass, the first bidirectional thyristor 9 and the second bidirectional thyristor 10 are turned on first, and after the first switch 7 and the second switch 8 are turned off and the fifth relay 5 and the sixth relay 6 are closed, the first bidirectional thyristor 9 and the second bidirectional thyristor 10 are turned off.

[0065] When the bypass is switched to off-grid, the first bidirectional thyristor 9 and the second bidirectional thyristor 10 are turned on first, and after the fifth relay 5 and the sixth relay 6 are disconnected and the first switch 7 and the second switch 8 are closed, the first bidirectional thyristor 9 and the second bidirectional thyristor 10 are turned off.

[0066] Example 2

[0067] exist Figure 2 In the grid-connected and off-grid switching circuit of the photovoltaic and energy storage integrated inverter shown, the first relay 1 and the third relay 3 are connected in series between the photovoltaic and energy storage integrated inverter 11 and the live wire L of the grid 12, and the second relay 2 and the fourth relay 4 are connected in series between the photovoltaic and energy storage integrated inverter 11 and the neutral wire N of the grid 12; one end of the fifth relay 5 is connected between the third relay 3 and the live wire L of the grid 12, and the other end is connected to the live wire L1 of the UPS load 13; one end of the sixth relay 6 is connected between the fourth relay 4 and the neutral wire N of the grid 12, and the other end is connected in series with the seventh relay 14 and then connected to the UPS The neutral line N1 of the load 13; the first bidirectional thyristor 9 is connected in parallel between the live line L of the power grid 12 and the live line L1 of the UPS load 13, and the second bidirectional thyristor 10 is connected in parallel between the neutral line N of the power grid 12 and the neutral line N1 of the UPS load 13; the photovoltaic and storage integrated inverter 11 is connected to the live line L1 of the UPS load 13 through the first switch 7, and is connected to the neutral line N1 of the UPS load 13 through the second switch 8. The first switch 7 and / or the second switch 8 can be any one of an automatic control switch, a manual control switch, an automatic control relay or a manual control relay.

[0068] The switching circuit has three modes: grid-connected, off-grid and bypass.

[0069] In the grid-connected mode, the first relay 1, the second relay 2, the third relay 3, the fourth relay 4, the fifth relay 5, the sixth relay 6, the seventh relay 14, the first switch 7, and the second switch 8 remain in the closed state, and the photovoltaic-storage integrated inverter 11 works in grid connection;

[0070] In off-grid mode, the first switch 7 and the second switch 8 remain closed, the first relay 1, the second relay 2, the third relay 3, the fourth relay 4, the fifth relay 5, the sixth relay 6, and the seventh relay 14 remain open, and the photovoltaic-storage integrated inverter 11 operates off-grid;

[0071] In bypass mode, the fifth relay 5, the sixth relay 6, and the seventh relay 14 remain closed, the first relay 1, the second relay 2, the third relay 3, the fourth relay 4, the first switch 7, and the second switch 8 remain open, and the power grid 12 supplies power to the UPS load 13.

[0072] The grid-connected and off-grid switching methods of this switching circuit are as follows:

[0073] When the grid-connected state is switched to the off-grid state, the first relay 1, the second relay 2, the third relay 3, the fourth relay 4, the fifth relay 5, the sixth relay 6, and the seventh relay 14 are disconnected, and the first switch 7 and the second switch 8 are always kept closed;

[0074] When switching from off-grid to grid-connected, the first relay 1, the second relay 2, the third relay 3, the fourth relay 4, the fifth relay 5, the sixth relay 6, and the seventh relay 14 are closed, and the first switch 7 and the second switch 8 are always kept closed.

[0075] The grid-connected and bypass switching methods of this switching circuit are as follows:

[0076] When the grid is switched to bypass, the first relay 1, the second relay 2, the third relay 3, the fourth relay 4, the first switch 7, and the second switch 8 are disconnected, and the fifth relay 5, the sixth relay 6, and the seventh relay 14 remain closed.

[0077] When the bypass is switched to grid connection, the first relay 1, the second relay 2, the third relay 3, the fourth relay 4, the first switch 7, and the second switch 8 are closed, and the fifth relay 5, the sixth relay 6, and the seventh relay 14 are always kept closed.

[0078] Off-grid and bypass switching methods of this switching circuit:

[0079] When the off-grid mode is switched to bypass, the first bidirectional thyristor 9 and the second bidirectional thyristor 10 are turned on first, and after the first switch 7 and the second switch 8 are turned off and the fifth relay 5, the sixth relay 6 and the seventh relay 14 are closed, the first bidirectional thyristor 9 and the second bidirectional thyristor 10 are turned off.

[0080] When the bypass is switched to off-grid, the first bidirectional thyristor 9 and the second bidirectional thyristor 10 are turned on first, and after the fifth relay 5, the sixth relay 6 and the seventh relay 14 are disconnected and the first switch 7 and the second switch 8 are closed, the first bidirectional thyristor 9 and the second bidirectional thyristor 10 are turned off.

Claims

1. The grid-connected and off-grid switching circuit of the photovoltaic and storage integrated inverter based on UPS load is characterized by: The first relay (1) and the third relay (3) are connected in series between the live wire L of the photovoltaic and energy storage integrated inverter (11) and the power grid (12); the second relay (2) and the fourth relay (4) are connected in series between the neutral wire N of the photovoltaic and energy storage integrated inverter (11) and the power grid (12); One end of the fifth relay (5) is connected between the third relay (3) and the live wire L of the power grid (12), and the other end is connected to the live wire L1 of the UPS load (13); one end of the sixth relay (6) is connected between the fourth relay (4) and the neutral wire N of the power grid (12), and the other end is connected to the neutral wire N1 of the UPS load (13); The first bidirectional thyristor (9) is connected in parallel between the live wire L of the power grid (12) and the live wire L1 of the UPS load (13), and the second bidirectional thyristor (10) is connected in parallel between the neutral wire N of the power grid (12) and the neutral wire N1 of the UPS load (13); The photovoltaic and energy storage integrated inverter (11) is connected to the live wire L1 of the UPS load (13) through a first switch (7), and is connected to the neutral wire N1 of the UPS load (13) through a second switch (8); The switching circuit has three modes: grid-connected, grid-off and bypass. In the grid-connected mode, the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the fifth relay (5), the sixth relay (6), the first switch (7), and the second switch (8) remain in a closed state; In the off-grid mode, the first switch (7) and the second switch (8) remain in a closed state, and the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the fifth relay (5), and the sixth relay (6) remain in an open state; In the bypass mode, the fifth relay (5) and the sixth relay (6) remain in a closed state, and the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the first switch (7), and the second switch (8) remain in an open state; When the off-grid mode is switched to bypass mode, the first bidirectional thyristor (9) and the second bidirectional thyristor (10) are first turned on, and after the fifth relay (5) and the sixth relay (6) are closed, the first bidirectional thyristor (9) and the second bidirectional thyristor (10) are turned off; When the bypass is switched to off-grid mode, the first bidirectional thyristor (9) and the second bidirectional thyristor (10) are first turned on, and after the first switch (7) and the second switch (8) are closed, the first bidirectional thyristor (9) and the second bidirectional thyristor (10) are turned off.

2. The UPS-based photovoltaic and storage integrated inverter on-grid and off-grid switching circuit according to claim 1, characterized in that: The first switch (7) and / or the second switch (8) are automatically controlled switches or manually controlled switches.

3. The UPS-based photovoltaic and storage integrated inverter on-grid and off-grid switching circuit according to claim 1, characterized in that: When the grid connection is switched to off-grid connection, the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the fifth relay (5), and the sixth relay (6) are disconnected, and the first switch (7) and the second switch (8) are always kept closed; When switching from off-grid to grid-connected, the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the fifth relay (5), and the sixth relay (6) are closed, and the first switch (7) and the second switch (8) are always kept closed.

4. The UPS-based photovoltaic and storage integrated inverter on-grid and off-grid switching circuit according to claim 1, characterized in that: When the grid connection is switched to bypass, the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the first switch (7), and the second switch (8) are disconnected, and the fifth relay (5) and the sixth relay (6) are always kept closed; When the bypass is switched to grid connection, the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the first switch (7), and the second switch (8) are closed, and the fifth relay (5) and the sixth relay (6) are always kept closed.

5. The grid-connected and off-grid switching circuit of the photovoltaic and storage integrated inverter based on UPS load is characterized by: The first relay (1) and the third relay (3) are connected in series between the live wire L of the photovoltaic and energy storage integrated inverter (11) and the power grid (12); the second relay (2) and the fourth relay (4) are connected in series between the neutral wire N of the photovoltaic and energy storage integrated inverter (11) and the power grid (12); One end of the fifth relay (5) is connected between the third relay (3) and the live wire L of the power grid (12), and the other end is connected to the live wire L1 of the UPS load (13); one end of the sixth relay (6) is connected between the fourth relay (4) and the neutral wire N of the power grid (12), and the other end is connected to the neutral wire N1 of the UPS load (13); The first bidirectional thyristor (9) is connected in parallel between the live wire L of the power grid (12) and the live wire L1 of the UPS load (13), and the second bidirectional thyristor (10) is connected in parallel between the neutral wire N of the power grid (12) and the neutral wire N1 of the UPS load (13); The photovoltaic and energy storage integrated inverter (11) is connected to the live wire L1 of the UPS load (13) through a first switch (7), and is connected to the neutral wire N1 of the UPS load (13) through a second switch (8); The other end of the sixth relay (6) is connected to the neutral line N1 of the UPS load (13) through the seventh relay (14); The switching circuit has three modes: grid-connected, grid-off and bypass. In the grid-connected mode, the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the fifth relay (5), the sixth relay (6), the seventh relay (14), the first switch (7), and the second switch (8) remain in a closed state; In the off-grid mode, the first switch (7) and the second switch (8) remain in a closed state, and the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the fifth relay (5), the sixth relay (6), and the seventh relay (14) remain in an open state; In the bypass mode, the fifth relay (5), the sixth relay (6), and the seventh relay (14) remain in a closed state, and the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the first switch (7), and the second switch (8) remain in an open state; When the off-grid mode is switched to bypass mode, the first bidirectional thyristor (9) and the second bidirectional thyristor (10) are first turned on, and after the fifth relay (5), the sixth relay (6) and the seventh relay (14) are closed, the first bidirectional thyristor (9) and the second bidirectional thyristor (10) are turned off; When the bypass is switched to off-grid mode, the first bidirectional thyristor (9) and the second bidirectional thyristor (10) are first turned on, and after the first switch (7) and the second switch (8) are closed, the first bidirectional thyristor (9) and the second bidirectional thyristor (10) are turned off.

6. The UPS-based photovoltaic and storage integrated inverter on-grid and off-grid switching circuit according to claim 5, characterized in that: When the grid connection is switched to off-grid connection, the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the fifth relay (5), the sixth relay (6), and the seventh relay (14) are disconnected, and the first switch (7) and the second switch (8) are always kept closed; When switching from off-grid to grid-connected, the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the fifth relay (5), the sixth relay (6), and the seventh relay (14) are closed, and the first switch (7) and the second switch (8) are always kept closed.

7. The UPS-based photovoltaic and storage integrated inverter on-grid and off-grid switching circuit according to claim 5, characterized in that: When the grid connection is switched to bypass, the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the first switch (7), and the second switch (8) are disconnected, and the fifth relay (5), the sixth relay (6), and the seventh relay (14) are always kept closed; When the bypass is switched to grid connection, the first relay (1), the second relay (2), the third relay (3), the fourth relay (4), the first switch (7), and the second switch (8) are closed, and the fifth relay (5), the sixth relay (6), and the seventh relay (14) are always kept closed.

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