Grid-connected and off-grid mode switching circuit and optical storage power supply system

Abstract

The utility model relates to a grid-connected and off-grid mode switching circuit and an optical storage power supply system, and the structure of a hardware circuit is changed, and a grid-connected and off-grid controller can be connected in series with the input side or the output side of a time delay module through the connection switching of a normally closed contact and a normally open contact of a newly added control relay. When the grid-connected and off-grid controller is connected in series with the input side of the time delay module, if a switch in the grid-connected and off-grid controller is switched off, low-voltage ride-through can be realized by switching to an off-grid state; and when the grid-connected and off-grid controller is connected in series with the output side of the time delay module, the grid-connected and off-grid contactor is immediately powered off and disconnected, so that quick off-grid can be realized. Therefore, through the change of the hardware circuit, the optical reserve power system with the optical reserve power system can realize selective working switching between the two modes of rapid off-grid and low voltage ride through, the compatibility is good, the operation of a user is facilitated, and the working reliability and stability of the optical reserve power system can be ensured through the overall adjustment of the hardware circuit.

Description

Technical Field

[0001] The utility model relates to the field of on-grid and off-grid control, in particular to an on-grid and off-grid mode switching circuit and an optical reserve power system. Background Art

[0002] like Figure 9 As shown, in addition to the AC grid 10 normally supplying power to the load 30 on the load side, the solar power reserve system also connects the DC power from the photovoltaic panel 20 and the energy storage battery 22 through the converter 21. The solar power reserve system generally has two operating modes:

[0003] 1. Off-grid mode: The on-grid and off-grid contactor 12 is disconnected. The load 30 is powered solely by the DC power generated by the photovoltaic panels 20 and / or the DC power stored in the energy storage battery 22, which is converted to AC power by the converter 21. When the power of the load 30 is lower than the power generated by the photovoltaic panels 20, the excess power can be used to charge the energy storage battery 22. Conversely, the energy storage battery 22 needs to discharge to compensate for the shortfall in power supplied by the photovoltaic panels 20 to the load 30.

[0004] 2. Grid-connected mode, i.e., the grid-connected / off-grid contactor 12 is closed. After the AC grid 10 is connected, the system can power the load 30 together with the photovoltaic panels 20 and the energy storage battery 22. Alternatively, the system can simultaneously power the load 30 and charge the energy storage battery 22 through the converter 21. Even when the load 30 power is low and the photovoltaic panels 20 are generating sufficient power, excess photovoltaic / battery energy can be fed back to the grid.

[0005] The switching between the two operating modes of the aforementioned solar power backup system depends on the on-off switching of the grid-connected and off-grid contactor 12. Generally speaking, in the event of a fault in the AC grid 10, to ensure stable power supply to the load 30, the grid-connected and off-grid contactor 12 must be disconnected as quickly as possible. However, in some regions, the grid may require the connected solar power backup system to have low voltage ride-through capability based on its own conditions. This means that the solar power backup system connected to the grid must be able to withstand a certain limit of low grid voltage for a certain period of time without shutting down. In short, this means that a brief voltage drop in the AC grid 10 will not cause the site to be disconnected from the grid.

[0006] In response to the low voltage ride-through requirements of the power grid in these areas, the commonly used technical means of the optical backup power system are as follows: Figure 10As shown. That is, coil 12.9 of on-grid contactor 12 uses a DC power supply, and a delay module 41 with a rectifier function is installed in front of it. When switch 40.1 on controller 40 is closed, the AC power from grid 10 is converted to DC by delay module 41, which then powers coil 12.9 of on-grid contactor 12, causing on-grid contactor 12 to close. When off-grid mode is required, disconnecting switch 40.1 also disconnects power to delay module 41. However, the small amount of energy stored in delay module 41 can maintain power for several seconds, delaying the opening of on-grid contactor 12. Ultimately, after coil 12.9 loses power, on-grid contactor 12 is released. Therefore, when a temporary low voltage occurs on grid 10, on-grid contactor 12 does not immediately open. When the voltage gradually recovers within two seconds, power to coil 12.9 is restored, allowing the contactor to remain closed, resulting in a successful ride-through. However, this approach results in a certain delay in each release action of the on-grid and off-grid contactor 12, rendering the solar backup power system inherently incapable of rapid off-grid switching. When the grid actually loses power, the load 30 may experience a temporary shutdown, or even require manual restart, causing inconvenience and even direct economic losses to the user. Therefore, users are forced to select backup power systems with different control methods based on the specific characteristics of their own grids, unable to flexibly switch operating modes based on their needs. Alternatively, if the grid characteristics change through modification, such as significantly reducing the probability of a true power outage and resulting in a temporary low voltage in most cases, users are forced to modify the on-grid and off-grid switching method through modification, which is costly. Utility Model Content

[0007] A main purpose of the present invention is to overcome at least one of the above-mentioned defects, and to provide an on-grid and off-grid mode switching circuit with working mode compatibility, which can enable the optical reserve power system to selectively operate in fast off-grid or low voltage ride-through mode, with low overall investment cost, high reliability and good stability.

[0008] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0009] The utility model provides a grid-connected and off-grid mode switching circuit, comprising a delay module and a grid-connected and off-grid contactor, wherein the input side of the delay module is connected to a power supply, and the output side of the delay module is connected to the grid-connected and off-grid contactor. The grid-connected and off-grid mode switching circuit also comprises a grid-connected and off-grid controller and a control relay, wherein:

[0010] A first input circuit and a second input circuit are provided between the power supply and the input side of the delay module, the normally open contact or normally closed contact of the control relay is connected in series to the first input circuit, and the normally closed contact or normally open contact of the control relay is connected in series to the second input circuit;

[0011] A first output circuit and a second output circuit are provided between the output side of the delay module and the grid-connected / off-grid contactor, the normally open contact or normally closed contact of the control relay is connected in series to the first output circuit, and the normally closed contact or normally open contact of the control relay is connected in series to the second output circuit;

[0012] When operating in different modes, the first input circuit and the first output circuit constitute a first circuit between the power supply, the grid-connected and off-grid controller, the delay module and the grid-connected and off-grid contactor, and the second input circuit and the second output circuit constitute a second circuit between the power supply, the delay module, the grid-connected and off-grid controller and the grid-connected and off-grid contactor;

[0013] The two ends of the on-grid and off-grid controller are connected in series to the first input circuit, and the two ends of the on-grid and off-grid controller are also connected in series to the second output circuit.

[0014] According to one embodiment of the present invention, one end of the power supply is connected to an input end of the delay module, and the other end of the power supply is connected in series with the normally open contact or normally closed contact of the control relay and the grid-connected and off-grid controller, and then connected to the other input end of the delay module, thereby forming the first input circuit;

[0015] One output end of the delay module is connected to one end of the grid-connected and off-grid contactor, and the other output end of the delay module is connected in series with the normally open contact or the normally closed contact of the control relay and then connected to the other end of the grid-connected and off-grid contactor, thus forming the first output circuit.

[0016] According to one embodiment of the present invention, the first circuit formed by the first input circuit and the first output circuit is a circuit in a low voltage ride-through working mode.

[0017] According to one embodiment of the present invention, one end of the power supply is connected to an input end of the delay module, and the other end of the power supply is connected in series with the normally closed contact or the normally open contact of the control relay and then connected to the other input end of the delay module, thereby forming the second input circuit;

[0018] One output end of the delay module is connected to one end of the grid-connected and off-grid contactor, and the other output end of the delay module is connected in series with the normally closed contact or normally open contact of the control relay and the grid-connected and off-grid controller, and then connected to the other end of the grid-connected and off-grid contactor, thereby forming the first output circuit.

[0019] According to one embodiment of the present invention, the second circuit formed by the second input circuit and the second output circuit is a circuit in a fast off-grid working mode.

[0020] According to one embodiment of the present invention, the relay coil of the control relay is independently powered, and the on / off of the power supply circuit of the relay coil is controlled by an external switch, and the grid-connected and off-grid mode switching circuit is controlled to switch between the first circuit and the second circuit according to whether the relay coil is powered.

[0021] According to one embodiment of the present invention, the power source is a DC power generation unit, an energy storage unit or an AC power grid.

[0022] According to one embodiment of the present invention, a rectifier unit is included, and the AC power grid is converted into DC power by the rectifier unit and then connected to the delay module or the on-grid controller.

[0023] According to one embodiment of the present invention, the rectifier unit is integrated into the delay module.

[0024] In particular, the present application also provides a photovoltaic reserve power system, including an AC power grid and an on-grid and off-grid contactor, wherein the AC power grid is connected to the DC side equipment and the load side through the on-grid and off-grid contactor, and it also includes the on-grid and off-grid mode switching circuit as described above, and the on-grid and off-grid mode switching circuit is used to control the photovoltaic reserve power system to switch between a low voltage ride-through working mode or a fast off-grid working mode.

[0025] Compared with the prior art, the advantages and beneficial effects of the grid-connected and off-grid mode switching circuit and the optical backup power system of the utility model patent application are:

[0026] The grid-connected and off-grid mode switching circuit of the present application, by changing the structure of the hardware circuit, can be switched by connecting the normally closed contacts and normally open contacts of the newly added control relay, or connecting the grid-connected and off-grid controller in series with the input side of the delay module, or connecting the grid-connected and off-grid controller in series with the output side of the delay module. When the grid-connected and off-grid controller is connected in series to the input side of the delay module, if the switch in the grid-connected and off-grid controller is disconnected and switched to off-grid, the delay module can still supply power to the grid-connected and off-grid contactor so that it remains attracted for a certain period of time, thereby achieving low voltage ride-through; when the grid-connected and off-grid controller is connected in series to the output side of the delay module, if the switch in the grid-connected and off-grid controller is disconnected and switched to off-grid, the grid-connected and off-grid contactor will immediately lose power and disconnect, thereby achieving rapid off-grid operation. Therefore, the present application can enable the optical reserve power system having the same to selectively switch between the two modes of rapid off-grid operation and low voltage ride-through operation through changes in the hardware circuit, has good compatibility, is convenient for users to operate, and the overall adjustment of the hardware circuit can ensure its working reliability and stability.

[0027] In addition, the present application only requires adding a relay to realize the switching adjustment of the circuit architecture, which has low investment cost and is easy to implement and promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0029] Figure 1 1 is a schematic structural diagram of an on-grid and off-grid mode switching circuit according to Example 1 of the present utility model;

[0030] Figure 2 1 is a schematic diagram of the circuit structure of the on-grid and off-grid mode switching circuit in the low voltage ride-through working mode according to Example 1 of the present utility model;

[0031] Figure 3 1 is a schematic diagram of the circuit structure of the on-grid and off-grid mode switching circuit in the fast off-grid working mode according to Example 1 of the present utility model;

[0032] Figure 4 This is a schematic structural diagram of an on-grid and off-grid mode switching circuit according to another implementation of Example 1 of the present invention, wherein a button card is used to control the relay coil;

[0033] Figure 5 2 is a schematic structural diagram of an on-grid and off-grid mode switching circuit according to Example 2 of the present utility model;

[0034] Figure 6 2 is a schematic structural diagram of an on-grid and off-grid mode switching circuit according to Example 3 of the present utility model;

[0035] Figure 7 1 is a schematic structural diagram of an on-grid and off-grid mode switching circuit according to Example 4 of the present utility model;

[0036] Figure 8 1 is a schematic structural diagram of an on-grid and off-grid mode switching circuit according to Example 5 of the present utility model;

[0037] Figure 9 This is a schematic diagram of the framework structure of the optical backup power system according to Example 6 of the present utility model;

[0038] Figure 10 The present invention is a structural diagram of a grid-connected and off-grid contactor control circuit with a low voltage ride-through function according to the prior art. DETAILED DESCRIPTION

[0039] The following is a clear and complete description of the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0040] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] Example 1:

[0042] This embodiment describes a grid-connected and off-grid mode switching circuit, including a delay module 41 and a grid-connected and off-grid contactor 12. The input side of the delay module 41 is connected to the AC grid 10 as a power source, and the output side of the delay module 41 is connected to the grid-connected and off-grid contactor 12. The grid-connected and off-grid mode switching circuit also includes a grid-connected and off-grid controller 40 and a control relay 12, wherein:

[0043] A first input circuit and a second input circuit are provided between the AC power grid 10 and the input side of the delay module 41. The normally closed contact of the control relay 12 is connected in series to the first input circuit, and the normally open contact of the control relay 12 is connected in series to the second input circuit.

[0044] A first output circuit and a second output circuit are provided between the output side of the delay module 41 and the grid-connected / off-grid contactor 12. The normally closed contact of the control relay 12 is connected in series to the first output circuit, and the normally open contact of the control relay 12 is connected in series to the second output circuit.

[0045] When operating in different modes, the first input circuit and the first output circuit constitute a first circuit between the power supply, the grid-connected / off-grid controller 40, the delay module 41 and the grid-connected / off-grid contactor 12, and the second input circuit and the second output circuit constitute a second circuit between the power supply, the delay module 41, the grid-connected / off-grid controller 40 and the grid-connected / off-grid contactor 12;

[0046] The two ends of the on-grid and off-grid controller 40 are connected in series to the first input circuit, and the two ends of the on-grid and off-grid controller 40 are also connected in series to the second output circuit.

[0047] In this embodiment, the power source is an AC power grid 10 , and a rectifier unit is integrated into the delay module 41 . The delay module 41 has four connection points, namely, two input terminals and two output terminals.

[0048] like Figure 1As shown, one end of the AC grid 10 is connected to an input end of the delay module 41, and the other end of the AC grid 10 is connected in series with the normally closed contact 42.1 of the control relay 12, the switch 40.1 in the grid-connected / off-grid controller 40, and the normally closed contact 42.3 of the control relay 12, and then connected to the other input end of the delay module 41, thereby forming the first input circuit; an output end of the delay module 41 is connected to one end of the grid-connected / off-grid contactor 12, and the other output end of the delay module 41 is connected in series with the normally closed contact 42.5 of the control relay 12, and then connected to the other end of the grid-connected / off-grid contactor 12, thereby forming the first output circuit.

[0049] One end of the AC grid 10 is connected to an input end of the delay module 41, and the other end of the AC grid 10 is connected in series with the normally open contact 42.2 of the control relay 12 and then connected to the other input end of the delay module 41, thereby forming a second input circuit; an output end of the delay module 41 is connected to one end of the grid-connected and off-grid contactor 12, and the other output end of the delay module 41 is connected in series with the normally open contact 42.4 of the control relay 12, the switch 40.1 of the grid-connected and off-grid controller 40, and the normally open contact 42.6 of the control relay 12, and then connected to the other end of the grid-connected and off-grid contactor 12, thereby forming a first output circuit.

[0050] It is not difficult to understand that the grid-connected and off-grid mode switching circuit of this embodiment, by changing the structure of the hardware circuit, can switch the connection of the normally closed contacts and normally open contacts of the newly added control relay 12, or connect the grid-connected and off-grid controller 40 in series to the input side of the delay module 41, or connect the grid-connected and off-grid controller 40 in series to the output side of the delay module 41.

[0051] In this embodiment, when the relay coil of the control relay 12 is not energized, the normally closed contacts 42.1, 42.3, and 42.5 remain closed, and the first circuit formed by the first input circuit and the first output circuit is as follows: Figure 2 As shown by the solid line in FIG, the on-grid / off-grid controller 40 is connected in series to the input side of the delay module 41. The first circuit is the circuit for the low voltage ride-through mode. In this state, if the switch 40.1 in the on-grid / off-grid controller 40 is disconnected and the circuit is switched to the off-grid mode, the delay module 41 can still supply power to the on-grid / off-grid contactor 12 to keep it closed for a certain period of time, thus achieving low voltage ride-through.

[0052] When the relay coil 12.9 of the control relay 12 is energized, the normally closed contacts 42.1, 42.3, and 42.5 are disconnected, while the normally open contacts 42.2, 42.4, and 42.6 are closed. The second circuit formed by the second input circuit and the second output circuit is as shown in FIG. Figure 3 As shown by the solid line in FIG, the on-grid / off-grid controller 40 is connected in series to the output side of the delay module 41. The second circuit is the circuit for the fast operating mode. In this state, if the switch 40.1 in the on-grid / off-grid controller 40 is opened and the off-grid mode is switched, the on-grid / off-grid contactor 12 will immediately lose power and disconnect, enabling a fast off-grid operation.

[0053] In this embodiment, the relay coil 12.9 of the control relay 12 is independently powered, and can be powered by an energy storage battery 22, a power generation device, or a direct current converted from the AC power grid 10. The power supply circuit of the relay coil 12.9 is turned on and off by an external switch. In this embodiment, the external switch for turning on and off the power supply circuit of the relay coil 12.9 is located in the on-grid controller 40.

[0054] Alternatively, a separate mechanical switch may be provided to control the on / off state of the power supply circuit of the relay coil 12.9. Figure 4 As shown, the button switch 43 is directly used to control the on / off of the power supply circuit of the relay coil 12.9. The basic functions of the present application can be realized through simple modification without upgrading the off-grid controller 40 and its software.

[0055] In addition, if the external switch for controlling the on / off of the power supply circuit of the relay coil 12.9 is set to other electrically controllable switches, such as a transistor, the relay 12 can also be controlled remotely, thereby realizing remote control switching between the fast off-grid mode and the low voltage ride-through mode.

[0056] Example 2:

[0057] The on-grid and off-grid mode switching circuit of this embodiment is adjusted based on the embodiment 1. The adjustment is that the delay module 41 used has six connection points, namely three input terminals and three output terminals. The input terminals and the output terminals correspond to each other. Figure 5 As shown, the first circuit and the second circuit can be isolated by the delay module 41, eliminating the normally closed contact 42.4 and the normally open contact 42.3 in the original embodiment 1, simplifying the requirements for the control relay 12.

[0058] Combining Example 1 and Example 2, it can be seen that by adjusting the selection of the delay module 41 and the control relay 12, the adaptive adjustment circuit can achieve the invention purpose of the present application. It is only necessary to control the attraction and disconnection of the relay 12 to realize the switching between the on-grid and off-grid controller 40 in series with the input side or the output side of the delay module 41. All of these should be protected by the present application and are not listed here one by one.

[0059] Example 3:

[0060] The on-grid and off-grid mode switching circuit of this embodiment is adjusted based on the embodiment 1. The adjustment is that the rectifier unit 50 is set independently. Figure 6 As shown, the AC power grid 10 is converted into DC power by the rectifier unit 50 and then connected to the delay module 41 or the grid-connected or off-grid controller 40. The subsequent connection circuit is basically the same as that in Example 1 and will not be repeated here.

[0061] Example 4:

[0062] The on-grid and off-grid mode switching circuit of this embodiment is adjusted based on the embodiment 1. Figure 7 As shown, the adjustment is that the power source directly adopted is a DC power supply 51, which can be a DC power generation unit or an energy storage unit, and the circuit does not need to be provided with a rectifier unit 50. The subsequent connection circuit is basically the same as that of Example 1 and will not be repeated here.

[0063] Example 5:

[0064] The on-grid and off-grid mode switching circuit of this embodiment is adjusted based on the embodiment 1. Figure 8 As shown, the adjustment is to swap the positions of the normally closed contact and the normally open contact in Example 1. It is not difficult to understand that since the first circuit of Example 1 is provided with a normally closed contact and the second circuit is provided with a normally open contact, then adjusting the normally closed contact in the first circuit to a normally open contact and the normally open contact in the second circuit to a normally closed contact can undoubtedly also solve the technical problem.

[0065] The only difference is that in the original embodiment 1, when the control relay 12 is not energized, the low voltage ride-through working mode is realized, and when it is energized, the fast off-grid working mode is realized; in this embodiment, when the control relay 12 is not energized, the fast off-grid working mode is realized, and when it is energized, the low voltage ride-through working mode is realized.

[0066] Example 6:

[0067] This embodiment describes a light backup power system, the structure of which is as follows: Figure 9As shown, it can generally include an AC grid 10, a grid-side circuit breaker 11, a grid-connected and off-grid contactor 12, a photovoltaic panel 20, a converter 21, an energy storage battery 22, a converter-side circuit breaker 23, a load-side circuit breaker 31, and a load 30. The AC grid 10 is connected to the grid-connected coupling point via the grid-side circuit breaker 11 and the grid-connected and off-grid contactor 12. The DC-side devices are the photovoltaic panel 20, the converter 21, the energy storage battery 22, and the converter-side circuit breaker 23. The photovoltaic panel 20 and the energy storage battery 22 are all connected to the converter 21. The converter 21 is then connected to the grid-connected coupling point via the converter-side circuit breaker 23. The load 30 on the load side is connected to the grid-connected coupling point via the load-side circuit breaker 31 and draws power from the grid-connected coupling point.

[0068] The optical reserve power system of this embodiment also includes an on-grid and off-grid mode switching circuit as described in any one of Examples 1 to 5, and the on-grid and off-grid mode switching circuit is used to control the optical reserve power system to switch between a low voltage ride-through working mode or a fast off-grid working mode when switching off-grid.

[0069] In summary, this application enables a solar power backup system to selectively switch between fast off-grid and low-voltage ride-through modes through hardware circuit changes. This system offers excellent compatibility and ease of operation. Furthermore, adjustments to the hardware circuitry ensure operational reliability and stability. Furthermore, the system is low-cost and easy to implement and promote.

[0070] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A grid-connected and off-grid mode switching circuit, comprising a delay module and an on-grid and off-grid contactor, wherein the input side of the delay module is connected to a power supply, and the output side of the delay module is connected to the on-grid and off-grid contactor, characterized in that: The on-grid and off-grid mode switching circuit also includes an on-grid and off-grid controller and a control relay, wherein: A first input circuit and a second input circuit are provided between the power supply and the input side of the delay module, the normally open contact or normally closed contact of the control relay is connected in series to the first input circuit, and the normally closed contact or normally open contact of the control relay is connected in series to the second input circuit; A first output circuit and a second output circuit are provided between the output side of the delay module and the grid-connected / off-grid contactor, the normally open contact or normally closed contact of the control relay is connected in series to the first output circuit, and the normally closed contact or normally open contact of the control relay is connected in series to the second output circuit; When operating in different modes, the first input circuit and the first output circuit constitute a first circuit between the power supply, the grid-connected and off-grid controller, the delay module and the grid-connected and off-grid contactor, and the second input circuit and the second output circuit constitute a second circuit between the power supply, the delay module, the grid-connected and off-grid controller and the grid-connected and off-grid contactor; The two ends of the on-grid and off-grid controller are connected in series to the first input circuit, and the two ends of the on-grid and off-grid controller are also connected in series to the second output circuit.

2. The on-grid and off-grid mode switching circuit according to claim 1, characterized in that: One end of the power supply is connected to an input end of the delay module, and the other end of the power supply is connected in series with the normally open contact or normally closed contact of the control relay and the grid-connected and off-grid controller, and then connected to the other input end of the delay module, thereby forming the first input circuit; One output end of the delay module is connected to one end of the grid-connected and off-grid contactor, and the other output end of the delay module is connected in series with the normally open contact or the normally closed contact of the control relay and then connected to the other end of the grid-connected and off-grid contactor, thus forming the first output circuit.

3. The on-grid and off-grid mode switching circuit according to claim 1 or 2, characterized in that: A first circuit formed by the first input circuit and the first output circuit is a circuit in a low voltage ride-through working mode.

4. The on-grid and off-grid mode switching circuit according to claim 1, characterized in that: One end of the power supply is connected to an input end of the delay module, and the other end of the power supply is connected in series with the normally closed contact or the normally open contact of the control relay and then connected to the other input end of the delay module, thereby forming the second input circuit; One output end of the delay module is connected to one end of the grid-connected and off-grid contactor, and the other output end of the delay module is connected in series with the normally closed contact or normally open contact of the control relay and the grid-connected and off-grid controller, and then connected to the other end of the grid-connected and off-grid contactor, thereby forming the first output circuit.

5. The on-grid and off-grid mode switching circuit according to claim 1 or 4, characterized in that: The second circuit formed by the second input circuit and the second output circuit is a circuit in a fast off-grid working mode.

6. The on-grid and off-grid mode switching circuit according to claim 1, characterized in that: The relay coil of the control relay is independently powered, and the on / off of the power supply circuit of the relay coil is controlled by an external switch, and the on-grid and off-grid mode switching circuit is controlled to switch between the first circuit and the second circuit according to whether the relay coil is powered.

7. The on-grid and off-grid mode switching circuit according to claim 1, characterized in that: The power source is a DC power generation unit, an energy storage unit or an AC power grid.

8. The on-grid and off-grid mode switching circuit according to claim 1, characterized in that: It includes a rectifier unit, and the AC power grid is converted into DC power by the rectifier unit and then connected to the delay module or the on-grid and off-grid controller.

9. The on-grid and off-grid mode switching circuit according to claim 7, characterized in that: The rectifier unit is integrated in the delay module.

10. A solar power reserve system comprising an AC grid and an on-grid and off-grid contactor, wherein the AC grid is connected to a DC side device and a load side via the on-grid and off-grid contactor, characterized in that: It comprises the on-grid and off-grid mode switching circuit according to any one of claims 1 to 9, wherein the on-grid and off-grid mode switching circuit is used to control the optical reserve power system to switch between a low voltage ride-through working mode or a fast off-grid working mode.

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