Standby power system and starting control method thereof

Abstract

According to the standby power system and the starting control method thereof provided by the invention, when the grid-connected and off-grid controller is powered off, the first control circuit provides the low-level signal to the second control circuit of the inverter as the off-grid signal, so that when the voltage of the direct current side of the inverter meets the condition of the starting voltage value of the inverter, off-grid black start is preferentially carried out, and the starting time of the inverter is shortened. And after starting is completed, off-grid operation outputs alternating current voltage to quickly supply power to a standby power load. And if the inverter detects that the voltage of the alternating current side meets the condition of the minimum off-grid output voltage value and receives a high-level signal as a grid-connected signal before the inverter is started in an off-grid mode to output the alternating current voltage, the inverter can be directly switched to be started in a grid-connected mode, and rapid starting is completed. When the voltage of the power grid meets the under-voltage protection voltage value condition, the grid-connected and off-grid controller can be directly started in a grid-connected mode to run in a grid-connected mode, the first switching circuit is closed, a high-level signal is sent to serve as a grid-connected signal, power is rapidly supplied to the standby power load, and meanwhile voltage is provided for the alternating current side of the inverter.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a backup power system and a startup control method thereof. Background Art

[0002] The whole-house backup power system is mainly composed of an inverter and an on-grid and off-grid controller. It can be powered by a variety of methods such as photovoltaic panels, energy storage devices and power grids to achieve stable power supply for household loads. Since the backup power system contains multiple power electronic devices such as inverters and on-grid and off-grid controllers, coordination between the power electronic devices is required to enable the backup power system to start quickly and run smoothly to supply power to household loads. In order to enable the backup power system to quickly provide continuous and stable power supply to the load, it is necessary for the backup power system to be able to start quickly under different power supply conditions to supply power to household loads. Summary of the invention

[0003] The present application provides a backup power system and a startup control method thereof, which are used to achieve rapid startup of the backup power system to supply power to household loads.

[0004] In the first aspect, the present application provides a backup power system, including: an inverter and an off-grid controller; the off-grid controller includes: a first switch circuit and a first control circuit, and the inverter includes: a second control circuit. The grid side of the first switch circuit is connected to the grid, the inverter side of the first switch circuit is connected to the AC side of the inverter, the DC side of the inverter is used to connect to the DC source, and the first control circuit is connected to the second control circuit. The first control circuit is used to: provide a low-level signal to the second control circuit when the off-grid controller is powered off; when the off-grid controller is powered on, detect whether the voltage of the grid is less than or equal to the undervoltage protection voltage value and whether the voltage of the inverter side is greater than or equal to the minimum off-grid output voltage value. The undervoltage protection voltage value is generally set to the voltage value of the first-level undervoltage protection point, for example, it can be set to 0.7Un, where Un is the rated value of the grid voltage. Only when the grid voltage is greater than the undervoltage protection voltage value can the off-grid controller be connected to the grid and run. Once the grid voltage is less than the undervoltage protection voltage value, the off-grid controller cannot be connected to the grid and can only switch to the off-grid mode. The minimum off-grid output voltage value is the minimum voltage value output by the inverter when it is running off-grid, for example, 50V can be selected. When the voltage on the inverter side of the off-grid controller is greater than or equal to the minimum off-grid output voltage value, it means that the inverter has completed off-grid startup and is running off-grid. If the voltage of the power grid is greater than the undervoltage protection voltage value and the voltage on the inverter side is less than the minimum off-grid output voltage value, the first switch circuit is closed and a high-level signal is provided to the second control circuit; if the voltage of the power grid is less than or equal to the undervoltage protection voltage value or the voltage on the inverter side is greater than or equal to the minimum off-grid output voltage value, the first switch circuit is disconnected and a low-level signal is provided to the second control circuit. The second control circuit is used to: when the inverter is powered on, detect whether the voltage on the DC side meets the inverter starting voltage value. The inverter starting voltage value is the minimum voltage value on the DC side that the inverter can start, for example, 120V can be selected. If the voltage on the DC side is greater than the inverter starting voltage value, it means that the inverter meets the starting conditions. If the voltage on the DC side is greater than the inverter starting voltage value, the voltage on the AC side is less than the minimum off-grid output voltage value and a low-level signal is received, the inverter is controlled to operate off-grid; if the voltage on the DC side is greater than the inverter starting voltage value, the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value and a high-level signal is received, the inverter is controlled to operate on-grid.

[0005] In the backup power system of the present application, corresponding grid-connected and off-grid starting conditions are set for the inverter and the grid-connected and off-grid controller. When the corresponding starting conditions are met, the inverter and the grid-connected and off-grid controller can be started separately on-grid or off-grid to realize rapid power supply to the backup power load.

[0006] Specifically, in the backup power system of the present application, since the first control circuit can provide a low-level signal as an off-grid signal to the second control circuit when the on-grid and off-grid controller is powered off, that is, when the inverter side and the grid side of the on-grid and off-grid controller are not powered, the inverter can be enabled to perform an off-grid black start first when the voltage on the DC side meets the inverter startup voltage value condition, and output AC voltage for off-grid operation after the startup is completed, and quickly supply power to the backup power load. The inverter does not need to wait for the control signal for indicating the on-grid or off-grid black start sent by the on-grid and off-grid controller or the system controller after power-on to perform the startup procedure. The startup method of the present application can enable the inverter to start off-grid when the voltage on the DC side meets the conditions after power-on, and the startup speed is fast, and the backup power load can be quickly supplied. In addition, after the inverter is off-grid, it supplies power to the on-grid and off-grid controller, so that the on-grid and off-grid controller performs an off-grid startup, keeps providing a low-level signal as an off-grid signal, and disconnects the first switch circuit, so that the backup power system operates off-grid. If, before the inverter outputs AC voltage during off-grid startup, it is detected that the voltage on the AC side of the inverter meets the minimum off-grid output voltage value condition and a high-level signal is received as a grid-connected signal, indicating that the off-grid controller has started to supply power to the backup load, the inverter can directly switch to grid-connected startup.

[0007] Specifically, in the backup power system of the present application, when the voltage of the grid meets the undervoltage protection voltage value condition, the grid-connected and off-grid controller can directly start from grid-connected to grid-connected operation, close the first switch circuit and send a high-level signal as a grid-connected signal, quickly supply power to the backup power load, and provide voltage to the AC side of the inverter. At this time, if the voltage on the DC side of the inverter meets the inverter startup voltage value condition, the inverter starts to grid-connected operation, and the backup power system is grid-connected. If during the grid-connected startup of the grid-connected and off-grid controller, before the grid-connected and off-grid controller closes the first switch circuit, it is detected that the voltage on the inverter side meets the minimum off-grid output voltage value condition, indicating that the inverter has started to supply power to the backup power load, the grid-connected and off-grid controller can be switched to off-grid startup, and subsequently, when the voltage of the grid meets the grid-connected conditions, off-grid switching and grid-connected operation can be performed.

[0008] In some embodiments of the present application, the first control circuit includes: a first control chip and a signal generating circuit. The signal generating circuit includes: a second switch circuit and a first resistor, the second switch circuit and the first resistor are connected in series between the ground port and the signal output port, and the second switch circuit is closed by default. When the first switch circuit in the on-grid and off-grid controller is disconnected, it means that the on-grid and off-grid controller is running off-grid, and the first control chip needs to close the second switch circuit so that the signal output port outputs a low-level signal, indicating off-grid. When the first switch circuit in the on-grid and off-grid controller is closed, it means that the on-grid and off-grid controller is running on-grid, and the first control chip needs to disconnect the second switch circuit so that the signal output port outputs a high-level signal, indicating grid connection.

[0009] In some embodiments of the present application, the second control circuit includes: a second control chip and a signal detection circuit. The signal detection circuit includes: an optocoupler, a second resistor, a first power supply and a second power supply, the first end of the optocoupler is connected to the first power supply, the second end of the optocoupler is connected to the signal input port, the signal input port of the signal detection circuit is connected to the signal output port of the signal generating circuit, the third end of the optocoupler is connected to the second power supply, the fourth end of the optocoupler is connected to the input end of the second control chip, and the second resistor is connected in series between the input end and the ground end of the second control chip. When the first switch circuit in the on-grid and off-grid controller is disconnected, it indicates that the on-grid and off-grid controller is off-grid, and the first control chip needs to close the second switch circuit so that the signal output port outputs a low-level signal, indicating that the on-grid and off-grid control instruction is off-grid, then the inverter starts off-grid and controls the inverter to operate off-grid. When the first switch circuit in the grid-connected and off-grid controller is closed, it means that the grid-connected and off-grid controller is running in grid connection. The first control chip needs to disconnect the second switch circuit, and the optocoupler in the signal detection circuit is disconnected, so that the signal output port outputs a high-level signal, indicating grid connection; at this time, the input end of the second control chip receives a low-level signal, indicating that the grid-connected and off-grid control instruction is grid-connected, then the inverter is started in grid connection, and the inverter is controlled to run in grid connection.

[0010] The above circuit structure can realize in hardware that the first control circuit provides a low-level signal as an off-grid signal by default when the on-grid and off-grid controller is not powered on, so that the second control circuit controls the inverter to start off-grid according to the off-grid signal. The off-grid operation of the inverter is in voltage source mode, and power is supplied to the backup load first.

[0011] In the present application, the backup power system has two power sources, the grid and the DC source. At this time, the voltage of the grid is greater than the undervoltage protection voltage value and the voltage on the DC side of the inverter is greater than the inverter starting voltage value. The grid-connected and off-grid controller and the inverter each execute their own startup process according to the above conditions provided in this application. During the startup process, the inverter can decide whether to switch the startup mode according to the voltage changes on the AC side and the grid-connected and off-grid signal changes. The grid-connected and off-grid controller can decide whether to switch the startup mode according to the voltage changes on the inverter side, so that the backup power system can adapt to the changes in power supply during the startup process and adjust the startup mode to give priority to ensuring the power supply of the backup power load.

[0012] In some embodiments of the present application, if the voltage of the power grid is greater than the undervoltage protection voltage value and the voltage on the DC side is greater than the inverter starting voltage value; the first control circuit is also used to: when the grid-connected and off-grid controller is powered on, control the grid-connected and off-grid controller to start, if the voltage on the inverter side is less than the minimum off-grid output voltage value, close the first switch circuit, and send a high-level signal to the second control circuit, so that when the voltage on the DC side of the second control circuit is greater than the inverter starting voltage value, control the inverter to grid-connected operation; if the voltage on the inverter side is greater than or equal to the minimum off-grid output voltage value, disconnect the first switch circuit and send a low-level signal to the second control circuit.

[0013] When the on-grid and off-grid controller is powered on, when the first control circuit detects that the voltage of the grid meets the undervoltage protection voltage value condition, the on-grid and off-grid controller starts to connect to the grid, and before closing the first switch circuit, detects whether the voltage on the inverter side meets the minimum off-grid output voltage value condition. If the voltage on the inverter side is less than the minimum off-grid output voltage value, it means that the inverter has not completed the off-grid startup and the off-grid operation supplies power to the backup load. Therefore, the first control circuit closes the first switch circuit and sends a high-level signal to the second control circuit as a grid-connected signal, and the on-grid and off-grid controller connects to the grid and supplies power to the backup load and the AC side of the inverter, so that when the voltage of the second control circuit of the inverter on the DC side is greater than the inverter startup voltage value, the inverter is controlled to connect to the grid, and the backup system is connected to the grid. If the voltage on the inverter side is greater than or equal to the minimum off-grid output voltage value, it means that the inverter has completed off-grid startup and is operating off-grid to supply power to the backup power load. The first control circuit does not need to close the first switch circuit, and keeps the first switch circuit open. It also keeps providing a low-level signal to the second control circuit as an off-grid signal, and the off-grid controller operates off-grid. At this point, the backup power system operates off-grid.

[0014] In some embodiments of the present application, if the voltage of the power grid is greater than the undervoltage protection voltage value and the voltage on the DC side is greater than the inverter starting voltage value; the second control circuit is also used to: receive a low-level signal when the inverter is powered on, control the inverter to start off-grid, if the voltage on the AC side is less than the minimum off-grid output voltage value and receives a low-level signal, control the inverter to operate off-grid; if the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value and receives a high-level signal, control the inverter to operate on-grid.

[0015] When the inverter is powered on, the second control circuit directly receives a low-level signal as an off-grid signal. When the second control circuit detects that the voltage on the DC side meets the inverter startup voltage value condition, the inverter starts off-grid, and detects whether the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value and whether a high-level signal is received as a grid-connected signal. Before the inverter outputs the AC voltage at off-grid startup, if the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value and a high-level signal is received, it means that the off-grid controller has completed the grid-connected startup and the grid-connected operation supplies power to the backup power load, then the inverter is controlled to switch to grid-connected operation, and the backup power system is now grid-connected. After the inverter off-grid startup is completed, the inverter off-grid operation supplies power to the load and the inverter side of the off-grid controller, and the off-grid controller operates off-grid, and the backup power system is now off-grid.

[0016] In some embodiments of the present application, if the voltage of the power grid is greater than the undervoltage protection voltage value and the voltage on the DC side is less than or equal to the inverter starting voltage value, the first control circuit is also used to: when the grid-connected and off-grid controller is powered on, close the first switch circuit and send a high-level signal to the second control circuit. When the backup power system is powered only by the power grid, when the grid-connected and off-grid controller is powered on, when the first control circuit of the grid-connected and off-grid controller detects that the voltage of the power grid meets the undervoltage protection voltage value condition, it executes grid-side startup, closes the first switch circuit and connects to the grid to supply power to the backup power load and the AC side of the inverter. In addition, the first control circuit sends a high-level signal to the second control circuit as a grid-connected signal, so that when the voltage on the DC side of the inverter meets the inverter starting voltage value, the second control circuit controls the inverter to connect to the grid.

[0017] In some embodiments of the present application, if the voltage on the DC side is greater than the inverter starting voltage value and the voltage of the power grid is less than or equal to the undervoltage protection voltage value, the second control circuit is also used to: when the inverter is powered on, control the inverter to operate off the grid. The backup power system is powered only by a DC source. When the inverter is powered on, the second control circuit of the inverter directly receives a low-level signal as an off-grid signal. When the second control circuit detects that the voltage on the DC side meets the inverter starting voltage value condition, the inverter is started off the grid, and the inverter is controlled to operate off the grid to supply power to the backup power load and the inverter side of the off-grid controller.

[0018] In some embodiments of the present application, it also includes: a power cable and a signal cable. The power cable is used to connect the inverter side of the first switch circuit and the AC side of the inverter, and the signal cable is used to connect the first control circuit and the second control circuit. The signal cable is independent of the power cable, which is beneficial to improving the reliability of signal transmission. The signal cable is used to realize the transmission of the on-grid and off-grid control signal, and the transmission of the off-grid signal may not depend on the power status of the on-grid and off-grid controller. Specifically, the first control circuit may provide a low-level signal as an off-grid signal to the second control circuit when the on-grid and off-grid controller is not powered on or powered off, so that the second control circuit controls the inverter to start off-grid according to the off-grid signal. The off-grid operation of the inverter is in the voltage source mode, and the backup load is powered first.

[0019] In some embodiments of the present application, the on-grid and off-grid controller includes: a first power-taking port, a second power-taking port, an inverter-side port and a grid-side port; the first power-taking port is used to connect to a backup power load, the second power-taking port is used to connect to a non-backup power load, the inverter-side port is connected to the AC side of the inverter, and the grid-side port is used to connect to the grid. The first switch circuit includes: a first relay and a second relay connected in series; the first relay is respectively connected to the first power-taking port and the inverter-side port, and the second relay is respectively connected to the second power-taking port and the grid-side port, so that the backup power load can be powered by the grid or inverter, and the non-backup power load is powered by the grid.

[0020] In a second aspect, the present application provides a startup control method for a backup power system, comprising:

[0021] When the grid-connected or off-grid controller is powered off, a low level signal is provided to the second control circuit of the inverter.

[0022] When the grid-connected and off-grid controller is powered on, if the voltage of the grid is greater than the undervoltage protection voltage value and the voltage on the inverter side is less than the minimum off-grid output voltage value, the first switch circuit in the grid-connected and off-grid controller is closed, and a high-level signal is sent to the second control circuit; if the voltage of the grid is less than or equal to the undervoltage protection voltage value or the voltage on the inverter side is greater than or equal to the minimum off-grid output voltage value, the first switch circuit is disconnected, and a low-level signal is sent to the second control circuit.

[0023] When the inverter is powered on, if the voltage on the DC side is greater than the inverter starting voltage value, the voltage on the AC side is less than the minimum off-grid output voltage value and a low-level signal is received, the inverter is controlled to operate off-grid; if the voltage on the DC side is greater than the inverter starting voltage value, the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value and a high-level signal is received, the inverter is controlled to operate on-grid.

[0024] In some embodiments of the present application, it also includes:

[0025] If the voltage of the grid is greater than the undervoltage protection voltage value and the voltage on the DC side is greater than the inverter starting voltage value, when the grid-connected and off-grid controller is powered on, the grid-connected and off-grid controller is controlled to start up; if the voltage on the inverter side is less than the minimum off-grid output voltage value, the first switch circuit is closed, and a high-level signal is sent to the second control circuit, so that when the voltage on the DC side of the second control circuit is greater than the inverter starting voltage value, the inverter is controlled to connect to the grid and operate; if the voltage on the inverter side is greater than or equal to the minimum off-grid output voltage value, the first switch circuit is disconnected, and a low-level signal is sent to the second control circuit.

[0026] In some embodiments of the present application, it also includes:

[0027] If the grid voltage is greater than the undervoltage protection voltage value and the DC side voltage is greater than the inverter start-up voltage value, a low-level signal is received when the inverter is powered on, and the inverter is controlled to start off-grid. If the AC side voltage is less than the minimum off-grid output voltage value and a low-level signal is received, the inverter is controlled to operate off-grid; if the AC side voltage is greater than or equal to the minimum off-grid output voltage value and a high-level signal is received, the inverter is controlled to operate on-grid.

[0028] In some embodiments of the present application, it also includes:

[0029] If the grid voltage is greater than the undervoltage protection voltage value and the DC side voltage is less than or equal to the inverter start-up voltage value, when the grid-connected and off-grid controller is powered on, the first switch circuit is closed and a high level signal is sent to the second control circuit.

[0030] In some embodiments of the present application, it also includes:

[0031] If the voltage on the DC side is greater than the inverter starting voltage value and the grid voltage is less than or equal to the undervoltage protection voltage value, the inverter is controlled to operate off-grid when the inverter is powered on. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the structure of the backup power system;

[0033] Figure 2 A schematic diagram of the structure of the backup power system provided in the embodiment of the present application;

[0034] Figure 3a A schematic diagram of the circuit structure of a single-phase on-grid and off-grid controller provided in an embodiment of the present application;

[0035] Figure 3b A schematic diagram of the circuit structure of a three-phase grid-connected and off-grid controller provided in an embodiment of the present application;

[0036] Figure 4 A schematic diagram of the circuit structure of the backup power system provided in an embodiment of the present application;

[0037] Figure 5A flowchart of a startup control method for a backup power system on the side of a grid-connected or off-grid controller provided in an embodiment of the present application;

[0038] Figure 6 A schematic diagram of a flow chart of a startup control method of a backup power system on the inverter side provided in an embodiment of the present application;

[0039] Figure 7 A flowchart of a startup control method for a backup power system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as being limited to the embodiments described herein; on the contrary, these embodiments are provided to make the present application more comprehensive and complete, and to fully convey the concepts of the example embodiments to those skilled in the art. The same figure marks in the figures represent the same or similar structures, and thus their repeated descriptions will be omitted. The words expressing position and direction described in this application are all explained using the accompanying drawings as examples, but changes may be made as needed, and all changes are included in the scope of protection of this application. The drawings of this application are only used to illustrate the relative position relationship and do not represent the true proportions.

[0041] It should be noted that specific details are described in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in a variety of other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific implementation methods disclosed below. The subsequent description of the specification is a preferred implementation method for implementing the present application, but the description is for the purpose of illustrating the general principles of the present application and is not intended to limit the scope of the present application. The scope of protection of the present application shall be determined by the definition of the attached claims.

[0042] In order to facilitate understanding of the embodiments of the present application, the relevant technologies involved in the embodiments of the present application are first introduced below.

[0043] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to be used as limitations on the present application. As used in the specification and appended claims of the present application, the singular expressions "one", "a kind of" and "the" are intended to also include expressions such as "one or more", unless there is a clear indication to the contrary in the context. It should also be understood that in the following embodiments of the present application, "at least one" refers to one, two or more than two.

[0044] References to "one embodiment" and the like described in this specification mean that a particular feature, structure or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. Thus, the phrases "in one embodiment", "in some embodiments", "in other embodiments", etc. that appear at different places in this specification do not necessarily all refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0045] Reference Figure 1 The backup power system mainly includes: an inverter and an on-grid and off-grid controller. The on-grid and off-grid controller is connected between the inverter and the power grid. The inverter is used to convert the DC power provided by the photovoltaic module or the energy storage device into AC power. The on-grid and off-grid controller includes: a first power supply port, a second power supply port, an inverter side port and a grid side port. The first power supply port is directly connected to the inverter side port, the second power supply port is directly connected to the grid side port, the inverter side port is connected to the AC side of the inverter, and the grid side port is used to connect to the power grid. Multiple inverters can be set in the backup power system. Accordingly, the on-grid and off-grid controller can be set with an inverter side port that is connected to the AC side of each inverter in a one-to-one correspondence. The household load connected to the on-grid and off-grid controller includes a backup load and a non-backup load. The first power supply port is used to connect to the backup load, and the second power supply port is used to connect to the non-backup load. The backup load can be powered by the power grid or the inverter, and the non-backup load is powered by the power grid.

[0046] The on-grid and off-grid controller includes a control chip and a relay. The control chip mainly realizes the on-grid and off-grid switching function of the inverter by controlling the closing and opening of the relay. When the grid is normal, the control chip controls the relay to close, and the backup power system runs on the grid to supply power to the backup power load; when the grid loses power, the control chip controls the relay to open, the inverter runs off-grid, and supplies power to the backup power load, thereby ensuring that the backup power load can always operate normally.

[0047] According to the power supply conditions when the backup power system is started, the backup power system can be divided into two startup modes: one is that when the voltage of the power grid meets the threshold conditions, the backup power system executes grid-side startup and operates on the grid; the other is that when the DC voltage provided by the photovoltaic module or energy storage device meets the threshold conditions, the backup power system executes inverter-side black start and operates off the grid.

[0048] At present, the startup method of the backup power system is: the grid-connected or off-grid controller directly starts the grid-connected or off-grid according to the communication instructions when powered on. After completing the closing or disconnection of the relay, the grid-connected or off-grid controller sends the corresponding startup signal to the inverter, and the inverter starts according to the detection results on the AC side and outputs AC power. When the grid-connected or off-grid controller is started off-grid, this solution needs to wait for the inverter to complete the startup before it can supply power to the backup power load, and it is impossible to quickly provide continuous and stable power supply to the load. In addition, if the power supply changes during the startup of the backup power system in a certain way, if the startup method cannot be adjusted in time, it will not be possible to complete the startup as soon as possible to ensure the power supply of the backup power load, which will also affect the customer experience.

[0049] Based on this, the backup power system and its startup control method provided in the embodiment of the present application can realize the rapid startup of the backup power system and provide continuous and stable power supply for the backup power load. In addition, if the power supply changes during the startup of the backup power system, the startup mode can be switched in time to ensure the power supply of the backup power load.

[0050] Reference Figure 2 , the backup power system provided in the embodiment of the present application includes an inverter and an on-grid and off-grid controller. The backup power system may also include a system controller, which is mainly used for system communication transmission, power scheduling, information reporting and other functions. Generally, the system controller is connected to the inverter and the on-grid and off-grid controller through an RS485 communication cable. The inverter is connected between the DC source and the on-grid and off-grid controller. The DC side of the inverter is used to connect to the DC source. The DC source can specifically be a photovoltaic module. The DC source can also be an energy storage device. The AC side of the inverter is connected to the inverter side of the on-grid and off-grid controller. The inverter is used to convert the DC power provided by the photovoltaic module or the energy storage device into AC power. The inverter may specifically include an inverter circuit, and may also include a DC conversion circuit. The DC conversion circuit is used to convert the DC power provided by the photovoltaic module into power. The inverter circuit is used to convert the DC power provided by the DC conversion circuit or the DC power provided by the energy storage device into AC power. The on-grid and off-grid controller may specifically include a first switch circuit, the grid side of the first switch circuit is used to connect to the power grid, and the inverter side of the first switch circuit is connected to the AC side of the inverter. In order to meet the requirements of power safety, the first switch circuit generally includes a two-stage switch, namely a first relay T1 and a second relay T2 connected in series. Figure 3a and Figure 3bThe grid-connected and off-grid controller generally includes four ports, specifically: a first power-drawing port, a second power-drawing port, an inverter side port and a grid side port. Among them, the first power-drawing port is used to connect to the backup power load, the second power-drawing port is used to connect to the non-backup power load, the inverter side port is used to connect to the AC side of the inverter, and the grid side port is used to connect to the power grid. The first relay T1 is respectively connected to the first power-drawing port and the inverter side port, and the second relay T2 is respectively connected to the second power-drawing port and the grid side port. Multiple inverters can be set in the backup power system, and accordingly, the grid-connected and off-grid controller can be set with an inverter side port that is connected one-to-one with the AC side of each inverter. Refer to Figure 3a The grid-connected and off-grid controller provided in this application can adopt a single-phase grid-connected and off-grid controller, or, referring to Figure 3b The grid-connected and off-grid controller provided in the present application may also adopt a three-phase grid-connected and off-grid controller. In addition, the grid-connected and off-grid controller may also include an NPE relay T3 connected between the neutral line N and the ground line PE, and a bypass switch T4 connected between the inverter side port and the grid side port.

[0051] The grid-connected and off-grid controller also includes a first control circuit, and the inverter also includes a second control circuit, and the first control circuit is connected to the second control circuit. The first control circuit and the second control circuit can be connected by a signal cable independent of the power cable to improve the reliability of signal transmission, and the power cable is a cable connected between the inverter side of the first switch circuit and the AC side of the inverter. The signal cable is used to realize the transmission of the grid-connected and off-grid control signal, and the transmission of the off-grid signal can be independent of the power state of the grid-connected and off-grid controller. Specifically, the first control circuit can provide a low-level signal as an off-grid signal to the second control circuit when the grid-connected and off-grid controller is not powered on, that is, when the inverter side and the grid side of the grid-connected and off-grid controller are not powered, so that the second control circuit controls the inverter to start off-grid according to the off-grid signal, and the off-grid operation of the inverter is in the voltage source mode, and the backup load is powered first. When the grid-connected and off-grid controller is powered on, according to the conditions satisfied by the voltage of the power grid, the first control circuit can provide a high-level signal as a grid-connected signal to the second control circuit, or provide a low-level signal as an off-grid signal, so that the second control circuit controls the inverter to perform grid-connected operation in current source mode according to the grid-connected signal, or controls the inverter to perform off-grid operation in voltage source mode according to the off-grid signal.

[0052] When there are multiple inverters in the backup power system, each inverter is connected to the corresponding inverter side port of the grid-connected and off-grid controller through a corresponding power cable, and the second control circuit of each inverter is connected to the first control circuit of the grid-connected and off-grid controller through a corresponding signal cable.

[0053] In the present application, in order to realize in hardware design that the first control circuit provides a low-level signal as an off-grid signal by default when the on-grid and off-grid controller is not powered on, a signal generating circuit for outputting on-grid and off-grid signals can be set in the first control circuit, and accordingly, a signal detection circuit for receiving on-grid and off-grid signals can be set in the second control circuit.

[0054] Reference Figure 4 , the first control circuit specifically includes a first control chip and a signal generating circuit, and the second control circuit includes a second control chip and a signal detection circuit. The signal generating circuit specifically includes: a second switch circuit K2 and a first resistor R1. Among them, the second switch circuit K2 and the first resistor R1 are connected in series between the ground port CGND and the signal output port. The second switch circuit K2 is in a closed state by default, and the second switch circuit K2 can specifically use a relay with normally closed contacts. The signal output port can provide a digital output (digital output, DO) signal. When the second switch circuit K2 is in a default closed state, the ground port CGND forms a path with the signal output port, and the DO signal is a low-level signal, indicating off-grid; after the first control chip controls the second switch circuit K2 to disconnect, the signal output port provides a high-level signal, that is, the DO signal is a high-level signal, indicating on-grid. Correspondingly, the signal detection circuit specifically includes: an optocoupler OC, a second resistor R2, a first power supply and a second power supply. Among them, the first end of the optocoupler OC is connected to the first power supply, which can be, for example, a 12V power supply, the second end of the optocoupler OC is connected to the signal input port, the signal input port of the signal detection circuit is connected to the signal output port of the signal generating circuit, the signal input port is used to receive the DO signal, the third end of the optocoupler OC is connected to the second power supply, which can be, for example, a 3.3V power supply, the fourth end of the optocoupler OC is connected to the input end of the second control chip, the second resistor is connected in series between the input end of the second control chip and the ground terminal AGND, and the input end of the second control chip is used to receive a digital input (DI) signal. Optionally, other resistors can be set on the line between the ground port CGND and the signal output port in the signal generating circuit, and other resistors can also be set on the line between the signal input port in the signal detection circuit and the input end of the second control chip, for example Figure 4 The resistor is shown by the dashed line.

[0055] When the first switch circuit in the on-grid and off-grid controller is disconnected, it means that the on-grid and off-grid controller is running off-grid, and the first control chip needs to close the second switch circuit K2, so that the signal output port outputs a low-level signal of the DO signal, indicating that it is off-grid; at this time, the optocoupler OC in the signal detection circuit is turned on, and the input end of the second control chip receives a high-level DI signal, indicating that the on-grid and off-grid control instruction is off-grid, then the inverter starts off-grid, and controls the inverter to run off-grid. When the first switch circuit in the on-grid and off-grid controller is closed, it means that the on-grid and off-grid controller is running on-grid, and the first control chip needs to disconnect the second switch circuit K2, and the optocoupler OC in the signal detection circuit is disconnected, so that the signal output port outputs a high-level signal of the DO signal, indicating that it is on-grid; at this time, the input end of the second control chip receives a low-level DI signal, indicating that the on-grid and off-grid control instruction is on-grid, then the inverter starts on-grid, and controls the inverter to run on-grid.

[0056] Reference Figure 5 When the grid-connected and off-grid controller is powered on, the first control circuit can detect whether the voltage of the grid is less than or equal to the undervoltage protection voltage value and whether the voltage on the inverter side is greater than or equal to the minimum off-grid output voltage value. The undervoltage protection voltage value is generally set to the voltage value of the first-level undervoltage protection point, for example, it can be set to 0.7Un, where Un is the rated value of the grid voltage. The grid-connected and off-grid controller can only be connected to the grid and operate. Once the grid voltage is less than the undervoltage protection voltage value, the grid-connected and off-grid controller cannot be connected to the grid and can only switch to the off-grid mode. The minimum off-grid output voltage value is the minimum voltage value output by the inverter when it is running off-grid, for example, 50V can be selected. When the voltage on the inverter side of the grid-connected and off-grid controller is greater than or equal to the minimum off-grid output voltage value, it means that the inverter has completed off-grid startup and off-grid operation. If the voltage of the power grid is less than or equal to the undervoltage protection voltage value or the voltage on the inverter side is greater than or equal to the minimum off-grid output voltage value, the first control circuit disconnects the first switch circuit and continues to provide a low-level signal to the second control circuit as an off-grid signal, and the off-grid controller enters the off-grid operation mode, at which time the backup power system is in off-grid operation to supply power to the backup power load. If the voltage of the power grid is greater than the undervoltage protection voltage value and the voltage on the inverter side is less than the minimum off-grid output voltage value, the first switch circuit is closed, a high-level signal is provided to the second control circuit, and the off-grid controller enters the grid-connected operation mode; at this time, if the voltage on the DC side of the inverter meets the inverter startup voltage value condition, the inverter will also be connected to the grid, so that the backup power system is in a grid-connected operation state to supply power to the backup power load.

[0057] Reference Figure 5 Optionally, when the on-grid and off-grid controller is powered on, it can first determine whether the communication with the inverter is normal. If the communication is normal, relevant system detection is performed. If the communication is abnormal, the system detection is skipped and priority is given to starting to prepare to supply power to the backup load.

[0058] Reference Figure 6 , when the inverter is powered on, the second control circuit can detect whether the voltage on the DC side meets the inverter startup voltage value condition. If the voltage on the DC side is greater than the inverter startup voltage value, the inverter startup voltage value is the minimum voltage value on the DC side that the inverter can start, for example, 120V can be selected, indicating that the inverter meets the startup condition, and the second control circuit detects whether the voltage on the AC side is less than the minimum off-grid output voltage value and whether a low-level signal is received as an off-grid signal. If the voltage on the AC side is less than the minimum off-grid output voltage value and a low-level signal is received, the second control circuit controls the inverter to run off-grid to supply power to the off-grid controller and the backup load. If the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value and a high-level signal is received as a grid-connected signal, it means that the off-grid controller has been connected to the grid to supply power to the backup load, and the second control circuit controls the inverter to run on the grid. If other detection results are obtained, such as the voltage on the AC side is less than the minimum off-grid output voltage value and a low-level signal is received, it means that the DO signal does not match the operating state of the off-grid controller, and an alarm is issued to shut down.

[0059] In the backup power system of the present application, since the first control circuit can provide a low-level signal as an off-grid signal to the second control circuit when the on-grid and off-grid controller is not powered on or powered off, the inverter can be enabled to perform an off-grid black start first when the voltage on the DC side meets the inverter startup voltage value condition, and output AC voltage for off-grid operation after the startup is completed to quickly supply power to the backup power load. In addition, after the inverter is off-grid, power is supplied to the on-grid and off-grid controller to enable the on-grid and off-grid controller to perform an off-grid startup, keep providing a low-level signal as an off-grid signal, and disconnect the first switch circuit to enable the backup power system to operate off-grid. If before the inverter outputs AC voltage during off-grid startup, it is detected that the voltage on the AC side of the inverter meets the minimum off-grid output voltage value condition and a high-level signal is received as a grid-connected signal, the inverter can directly switch to grid-connected startup.

[0060] In the backup power system of the present application, when the voltage of the grid meets the undervoltage protection voltage value condition, the grid-connected and off-grid controller can directly start from grid-connected to grid-connected operation, close the first switch circuit and send a high-level signal as a grid-connected signal, quickly supply power to the backup power load, and provide voltage to the AC side of the inverter at the same time. At this time, if the voltage on the DC side of the inverter meets the inverter startup voltage value condition, the inverter starts to grid-connected operation, and the backup power system runs in grid connection. If during the grid-connected startup of the grid-connected and off-grid controller, before the grid-connected and off-grid controller closes the first switch circuit, it is detected that the voltage on the inverter side meets the minimum off-grid output voltage value condition, then the grid-connected and off-grid controller can be switched to off-grid startup, and subsequently when the voltage of the grid meets the grid-connected conditions, off-grid switching and grid-connected operation can be performed.

[0061] Specifically, when the backup power system provided by the present application is started, there are the following power supply situations:

[0062] 1. The backup power system is powered only by the grid. At this time, the voltage of the grid is greater than the undervoltage protection voltage value and the voltage on the DC side of the inverter is less than or equal to the inverter startup voltage value. When the on-grid controller is powered on, when the first control circuit of the on-grid controller detects that the voltage of the grid meets the undervoltage protection voltage value condition, the grid side is started, and the first switch circuit is closed for grid-connected operation to supply power to the backup load and the AC side of the inverter. In addition, the first control circuit sends a high-level signal to the second control circuit as a grid-connected signal, so that when the voltage on the DC side of the inverter meets the inverter startup voltage value, the second control circuit controls the inverter to connect to the grid.

[0063] 2. The backup power system is powered only by a DC source. At this time, the voltage on the DC side is greater than the inverter starting voltage value and the voltage of the grid is less than or equal to the undervoltage protection voltage value. When the inverter is powered on, the second control circuit of the inverter directly receives a low-level signal as an off-grid signal. When the second control circuit detects that the voltage on the DC side meets the inverter starting voltage value condition, the inverter off-grid start is executed, and the inverter off-grid operation is controlled to supply power to the backup power load and the inverter side of the off-grid controller.

[0064] 3. The backup power system has two power sources, the grid and the DC source. At this time, the voltage of the grid is greater than the undervoltage protection voltage value and the voltage on the DC side of the inverter is greater than the inverter starting voltage value. The grid-connected and off-grid controller and the inverter each execute their own startup process according to the above conditions provided in this application. During the startup process, the inverter can decide whether to switch the startup mode according to the voltage changes on the AC side and the DO signal changes. The grid-connected and off-grid controller can decide whether to switch the startup mode according to the voltage changes on the inverter side, so that the backup power system can adapt to the changes in power supply during the startup process and adjust the startup mode, giving priority to ensuring the power supply of the backup power load. The detailed switching startup process is as follows.

[0065] Reference Figure 7When the on-grid and off-grid controller is powered on, when the first control circuit detects that the voltage of the grid meets the undervoltage protection voltage value condition, the on-grid and off-grid controller starts to connect to the grid, and before closing the first switch circuit, detects whether the voltage on the inverter side meets the minimum off-grid output voltage value condition. If the voltage on the inverter side is less than the minimum off-grid output voltage value, it means that the inverter has not completed the off-grid startup and the off-grid operation supplies power to the backup load. Therefore, the first control circuit closes the first switch circuit and sends a high-level signal to the second control circuit as a grid-connected signal. The on-grid and off-grid controller connects to the grid and supplies power to the backup load and the AC side of the inverter, so that when the voltage of the second control circuit of the inverter on the DC side is greater than the inverter startup voltage value, the inverter is controlled to connect to the grid. At this point, the backup power system is connected to the grid and operates. If the voltage on the inverter side is greater than or equal to the minimum off-grid output voltage value, it means that the inverter has completed off-grid startup and is operating off-grid to supply power to the backup power load. The first control circuit does not need to close the first switch circuit, and keeps the first switch circuit open. It also keeps providing a low-level signal to the second control circuit as an off-grid signal, and the off-grid controller operates off-grid. At this point, the backup power system operates off-grid.

[0066] Reference Figure 7 When the inverter is powered on, the second control circuit directly receives a low-level signal as an off-grid signal. When the second control circuit detects that the voltage on the DC side meets the inverter startup voltage value condition, the inverter starts off-grid, and detects whether the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value and whether a high-level signal is received as a grid-connected signal. Before the inverter starts to output the AC voltage off-grid, if the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value and a high-level signal is received, it means that the off-grid controller has completed the grid-connected startup and the grid-connected operation supplies power to the backup power load, then the inverter is controlled to switch to grid-connected operation, and the backup power system is now grid-connected. Optionally, before controlling the inverter to switch to grid-connected operation, it is also possible to determine again whether the voltage on the DC side of the inverter meets the inverter startup voltage value condition. After determining that the voltage on the DC side is greater than the inverter startup voltage value, the inverter switches to grid-connected operation. Before the inverter starts to output AC voltage off-grid, if the voltage on the AC side is less than the minimum off-grid output voltage value or has been receiving a low-level signal, the inverter will run off-grid to supply power to the load and the inverter side of the off-grid controller, and the off-grid controller will run off-grid. At this point, the backup power system will run off-grid.

[0067] Based on the same inventive concept, the present application also provides a startup control method for the above backup power system, comprising the following steps:

[0068] When the grid-connected or off-grid controller is powered off, a low level signal is provided to the second control circuit of the inverter.

[0069] When the grid-connected and off-grid controller is powered on, if the voltage of the grid is greater than the undervoltage protection voltage value and the voltage on the inverter side is less than the minimum off-grid output voltage value, the first switch circuit in the grid-connected and off-grid controller is closed, and a high-level signal is sent to the second control circuit; if the voltage of the grid is less than or equal to the undervoltage protection voltage value or the voltage on the inverter side is greater than or equal to the minimum off-grid output voltage value, the first switch circuit is disconnected, and a low-level signal is sent to the second control circuit.

[0070] When the inverter is powered on, if the voltage on the DC side is greater than the inverter starting voltage value, the voltage on the AC side is less than the minimum off-grid output voltage value and a low-level signal is received, the inverter is controlled to operate off-grid; if the voltage on the DC side is greater than the inverter starting voltage value, the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value and a high-level signal is received, the inverter is controlled to operate on-grid.

[0071] In some embodiments of the present application, it also includes:

[0072] If the voltage of the grid is greater than the undervoltage protection voltage value and the voltage on the DC side is greater than the inverter starting voltage value, when the grid-connected and off-grid controller is powered on, the grid-connected and off-grid controller is controlled to start up; if the voltage on the inverter side is less than the minimum off-grid output voltage value, the first switch circuit is closed, and a high-level signal is sent to the second control circuit, so that when the voltage on the DC side of the second control circuit is greater than the inverter starting voltage value, the inverter is controlled to connect to the grid and operate; if the voltage on the inverter side is greater than or equal to the minimum off-grid output voltage value, the first switch circuit is disconnected, and a low-level signal is sent to the second control circuit.

[0073] In some embodiments of the present application, it also includes:

[0074] If the grid voltage is greater than the undervoltage protection voltage value and the DC side voltage is greater than the inverter start-up voltage value, a low-level signal is received when the inverter is powered on, and the inverter is controlled to start off-grid. If the AC side voltage is less than the minimum off-grid output voltage value and a low-level signal is received, the inverter is controlled to operate off-grid; if the AC side voltage is greater than or equal to the minimum off-grid output voltage value and a high-level signal is received, the inverter is controlled to operate on-grid.

[0075] In some embodiments of the present application, it also includes:

[0076] If the grid voltage is greater than the undervoltage protection voltage value and the DC side voltage is less than or equal to the inverter start-up voltage value, when the grid-connected and off-grid controller is powered on, the first switch circuit is closed and a high level signal is sent to the second control circuit.

[0077] In some embodiments of the present application, it also includes:

[0078] If the voltage on the DC side is greater than the inverter startup voltage value and the grid voltage is less than or equal to the undervoltage protection voltage value, when the inverter is powered on, the inverter is controlled to operate off-grid.

[0079] The above-mentioned backup power system and its startup control method provided by the present application are that when the grid-connected and off-grid controller is powered off, the first control circuit provides a low-level signal to the second control circuit of the inverter as an off-grid signal, so that when the voltage on the DC side of the inverter meets the inverter startup voltage value condition, the inverter will give priority to off-grid black start, and output AC voltage for off-grid operation after the startup is completed, and quickly supply power to the backup power load. If before the inverter outputs AC voltage during off-grid startup, it is detected that the voltage on the AC side meets the minimum off-grid output voltage value condition and a high-level signal is received as a grid-connected signal, the inverter can directly switch to grid-connected startup to complete the quick startup. When the voltage of the power grid meets the undervoltage protection voltage value condition, the grid-connected and off-grid controller can directly start from the grid to the grid-connected operation, close the first switch circuit and send a high-level signal as a grid-connected signal, quickly supply power to the backup power load, and provide voltage to the AC side of the inverter at the same time.

[0080] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A backup power system, characterized in that: include: Inverter and on-grid and off-grid controller; The on-grid and off-grid controller comprises: a first switch circuit and a first control circuit, and the inverter comprises: a second control circuit; The grid side of the first switch circuit is connected to the grid, the inverter side of the first switch circuit is connected to the AC side of the inverter, the DC side of the inverter is used to be connected to a DC source, and the first control circuit is connected to the second control circuit; The first control circuit is used to: provide a low level signal to the second control circuit when the on-grid and off-grid controller is powered off; When the grid-connected and off-grid controller is powered on, if the voltage of the grid is greater than the undervoltage protection voltage value and the voltage of the inverter side is less than the minimum off-grid output voltage value, the first switch circuit is closed and a high-level signal is provided to the second control circuit; if the voltage of the grid is less than or equal to the undervoltage protection voltage value or the voltage of the inverter side is greater than or equal to the minimum off-grid output voltage value, the first switch circuit is opened and the low-level signal is provided to the second control circuit; The second control circuit is used for: when the inverter is powered on, if the voltage on the DC side is greater than the inverter starting voltage value, the voltage on the AC side is less than the minimum off-grid output voltage value and the low-level signal is received, controlling the inverter to operate off-grid; if the voltage on the DC side is greater than the inverter starting voltage value, the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value and the high-level signal is received, controlling the inverter to operate on-grid.

2. The backup power system according to claim 1, characterized in that: The first control circuit includes: a first control chip and a signal generating circuit; The signal generating circuit comprises: a second switch circuit and a first resistor, wherein the second switch circuit and the first resistor are connected in series between a ground port and a signal output port, and the second switch circuit is in a closed state by default; The first control chip is used to open the second switch circuit when the first switch circuit is closed, so that the signal output port outputs the high level signal, and to close the second switch circuit when the first switch circuit is opened, so that the signal output port outputs the low level signal.

3. The backup power system according to claim 2, characterized in that: The second control circuit includes: a second control chip and a signal detection circuit; The signal detection circuit includes: an optocoupler, a second resistor, a first power supply and a second power supply, wherein the first end of the optocoupler is connected to the first power supply, the second end of the optocoupler is connected to a signal input port, the signal input port is connected to the signal output port, the third end of the optocoupler is connected to the second power supply, the fourth end of the optocoupler is connected to the input end of the second control chip, and the second resistor is connected in series between the input end and the ground end of the second control chip; The second control chip is used to receive a low level signal when the signal output port outputs the high level signal, and control the inverter to operate in grid connection if the voltage on the DC side is greater than the inverter starting voltage value and the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value; and receive a high level signal when the signal output port outputs the low level signal, and control the inverter to operate in off-grid mode if the voltage on the DC side is greater than the inverter starting voltage value and the voltage on the AC side is less than the minimum off-grid output voltage value.

4. The backup power system according to any one of claims 1 to 3, characterized in that: If the voltage of the grid is greater than the undervoltage protection voltage value and the voltage of the DC side is greater than the inverter starting voltage value; the first control circuit is also used for: When the on-grid and off-grid controller is powered on, the on-grid and off-grid controller is controlled to start up in grid connection, and if the voltage on the inverter side is less than the minimum off-grid output voltage value, the first switch circuit is closed, and the high level signal is sent to the second control circuit; If the voltage on the inverter side is greater than or equal to the minimum off-grid output voltage value, the first switch circuit is disconnected and the low level signal is sent to the second control circuit.

5. The backup power system according to any one of claims 1 to 4, characterized in that: If the voltage of the grid is greater than the undervoltage protection voltage value and the voltage of the DC side is greater than the inverter start-up voltage value; the second control circuit is also used for: When the inverter is powered on, the low-level signal is received to control the inverter to start off-grid. If the voltage on the AC side is less than the minimum off-grid output voltage value and the low-level signal is received, the inverter is controlled to operate off-grid; if the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value and the high-level signal is received, the inverter is controlled to operate on-grid.

6. The backup power system according to any one of claims 1 to 5, characterized in that: If the voltage of the grid is greater than the undervoltage protection voltage value and the voltage of the DC side is less than or equal to the inverter starting voltage value; the first control circuit is further used for: When the grid-connected and off-grid controller is powered on, the first switch circuit is closed and the high level signal is sent to the second control circuit.

7. The backup power system according to any one of claims 1 to 6, characterized in that: If the voltage of the DC side is greater than the inverter startup voltage value and the voltage of the grid is less than or equal to the undervoltage protection voltage value, the second control circuit is further used to: When the inverter is powered on, the inverter is controlled to operate off-grid.

8. The backup power system according to any one of claims 1 to 7, characterized in that: Also includes: Power cables and signal cables; The power cable is used to connect the inverter side of the first switch circuit and the AC side of the inverter, and the signal cable is used to connect the first control circuit and the second control circuit.

9. The backup power system according to any one of claims 1 to 8, characterized in that: The on-grid and off-grid controller comprises: a first power-taking port, a second power-taking port, an inverter-side port and a grid-side port; the first power-taking port is used to connect to a backup power load, the second power-taking port is used to connect to a non-backup power load, the inverter-side port is connected to the AC side of the inverter, and the grid-side port is used to connect to the power grid; The first switch circuit includes: a first relay and a second relay connected in series; the first relay is connected to the first power-taking port and the inverter-side port respectively, and the second relay is connected to the second power-taking port and the grid-side port respectively.

10. A startup control method for a backup power system, characterized in that: include: When the grid-connected and off-grid controller is powered off, a low-level signal is provided to the second control circuit of the inverter; when the grid-connected and off-grid controller is powered on, if the voltage of the grid is greater than the undervoltage protection voltage value and the voltage on the inverter side of the grid-connected and off-grid controller is less than the minimum off-grid output voltage value, the first switch circuit in the grid-connected and off-grid controller is closed, and a high-level signal is sent to the second control circuit; If the voltage of the grid is less than or equal to the undervoltage protection voltage value or the voltage of the inverter side is greater than or equal to the minimum off-grid output voltage value, disconnect the first switch circuit and send the low level signal to the second control circuit; When the inverter is powered on, if the voltage on the DC side of the inverter is greater than the inverter starting voltage value, the voltage on the AC side of the inverter is less than the minimum off-grid output voltage value and the low-level signal is received, the inverter is controlled to operate off-grid; if the voltage on the DC side is greater than the inverter starting voltage value, the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value and the high-level signal is received, the inverter is controlled to operate on-grid.

11. The startup control method according to any one of claims 10, characterized in that: Also includes: If the voltage of the grid is greater than the undervoltage protection voltage value and the voltage of the DC side is greater than the inverter startup voltage value, when the grid-connected and off-grid controller is powered on, the grid-connected and off-grid controller is controlled to start up, and if the voltage of the inverter side is less than the minimum off-grid output voltage value, the first switch circuit is closed, and the high level signal is sent to the second control circuit; If the voltage on the inverter side is greater than or equal to the minimum off-grid output voltage value, the first switch circuit is disconnected and the low level signal is sent to the second control circuit.

12. The startup control method according to claim 10 or 11, characterized in that: Also includes: If the voltage of the power grid is greater than the undervoltage protection voltage value and the voltage on the DC side is greater than the inverter starting voltage value, the low-level signal is received when the inverter is powered on, and the inverter is controlled to start off-grid; if the voltage on the AC side is less than the minimum off-grid output voltage value and the low-level signal is received, the inverter is controlled to operate off-grid; if the voltage on the AC side is greater than or equal to the minimum off-grid output voltage value and the high-level signal is received, the inverter is controlled to operate on-grid.

13. The startup control method according to any one of claims 10 to 12, characterized in that: Also includes: If the voltage of the grid is greater than the undervoltage protection voltage value and the voltage on the DC side is less than or equal to the inverter starting voltage value, when the grid-connected and off-grid controller is powered on, the first switch circuit is closed and the high level signal is sent to the second control circuit.

14. The startup control method according to any one of claims 10 to 13, characterized in that: Also includes: If the voltage on the DC side is greater than the inverter startup voltage value and the voltage of the grid is less than or equal to the undervoltage protection voltage value, when the inverter is powered on, the inverter is controlled to operate off-grid.

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