Auxiliary power supply system for photovoltaic inverters

Abstract

This application discloses an auxiliary power supply system for a photovoltaic inverter, including a DC auxiliary power supply, a first AC auxiliary power supply, a second AC auxiliary power supply, a rectifier unit, a first controllable switch, and a second controllable switch. The input terminal of the rectifier unit is connected to the AC power grid via the first controllable switch, and the output terminal of the rectifier unit is connected to the input terminal of the first AC auxiliary power supply and one end of the second controllable switch. The other end of the second controllable switch is connected to the input terminal of the second AC auxiliary power supply. The input terminal of the DC auxiliary power supply is connected to the photovoltaic string, and the output terminals of the DC auxiliary power supply, the first AC auxiliary power supply, and the second AC auxiliary power supply are used to provide power to the load. The control terminals of the first and second controllable switches are used to receive control signals to turn the system on or off under the action of the control signals. This application allows for flexible switching of the AC auxiliary power supply to reduce losses, based on the user's actual application scenarios.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to an auxiliary power supply system for a photovoltaic inverter. Background Technology

[0002] Currently, in photovoltaic inverters, auxiliary power supplies typically power the system's sampling unit, control unit, drive unit, and communication unit. Based on the power source, auxiliary power supplies can be categorized into DC auxiliary power supplies and AC auxiliary power supplies. DC auxiliary power supplies draw power from the system's DC bus, while AC auxiliary power supplies draw power from the AC grid. A drawback of existing auxiliary power supplies is that while the photovoltaic inverter does not generate electricity at night, the AC auxiliary power supply continues to consume power, resulting in high standby power consumption for the photovoltaic inverter at night. Numerous scholars have researched this issue, and current solutions mainly fall into four categories:

[0003] (1) Directly shut down the AC auxiliary power source

[0004] (2) Shut down the system's drive circuit

[0005] (3) Indirect work of exchanging auxiliary resources

[0006] (4) Add a relay on the power grid side to disconnect the power grid at night.

[0007] While these solutions can reduce nighttime power consumption of photovoltaic inverters, they suffer from drawbacks such as high cost, limited effectiveness, and complex circuitry. Furthermore, these solutions address the problem from the product perspective. For users, inverter use is confined to specific operating environments; generally, simply setting the inverter to a fixed mode and having the auxiliary power source operate under predetermined conditions is sufficient to meet user needs. Therefore, addressing the issue of nighttime power consumption of inverters from the user's perspective is crucial. Utility Model Content

[0008] This application provides an auxiliary power supply system for a photovoltaic inverter to reduce the nighttime power consumption of the photovoltaic inverter.

[0009] This application provides an auxiliary power supply system for a photovoltaic inverter, the auxiliary power supply system including a DC auxiliary power supply, a first AC auxiliary power supply, a second AC auxiliary power supply, a rectifier unit, a first controllable switch, and a second controllable switch;

[0010] The input terminal of the rectifier unit is connected to the AC power grid through the first controllable switch, the output terminal of the rectifier unit is connected to the input terminal of the first AC auxiliary power supply and one end of the second controllable switch, and the other end of the second controllable switch is connected to the input terminal of the second AC auxiliary power supply.

[0011] The input terminal of the DC auxiliary power supply is connected to the photovoltaic string, and the output terminals of the DC auxiliary power supply, the first AC auxiliary power supply, and the second AC auxiliary power supply are used to provide power to the load.

[0012] The control terminals of the first and second controllable switches are used to receive control signals, so as to turn on or off under the action of the control signals.

[0013] The auxiliary power supply system for the photovoltaic inverter provided in this application can flexibly turn the AC auxiliary power supply on and off to reduce losses based on the user's actual application scenario. Specifically, the operating mode of the AC auxiliary power supply can be preset according to the user's usage environment and preferences, with the lowest loss in operating mode 0 at night, the highest loss in operating mode 2, and the intermediate loss in operating mode 1. It can also identify the photovoltaic output voltage, grid voltage, and wake-up signal. During the day, when the photovoltaic output voltage is greater than a preset voltage threshold, such as 180V, the AC auxiliary power supply is automatically woken up. At night, when a wake-up signal is detected, the AC auxiliary power supply is also woken up. When there is no wake-up signal at night, and the photovoltaic output voltage is lower than a preset voltage threshold, such as 100V, and the grid is normal, the AC auxiliary power supply operates in the user-set mode. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the auxiliary power supply system for a photovoltaic inverter provided in an embodiment of this application;

[0015] Figure 2 A schematic diagram of the first execution unit provided in an embodiment of this application;

[0016] Figure 3 A schematic diagram of the second execution unit provided in an embodiment of this application;

[0017] Figure 4 A schematic diagram of the first detection unit provided in an embodiment of this application;

[0018] Figure 5 This is a schematic diagram of the second detection unit provided in an embodiment of this application;

[0019] Figure 6 This is a schematic diagram of the working process of the auxiliary power supply system provided in the embodiments of this application.

[0020] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer and more understandable, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.

[0022] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] like Figure 1 As shown in the figure, this application embodiment provides an auxiliary power supply system for a photovoltaic inverter. The auxiliary power supply system includes a DC auxiliary power supply (shown as DC auxiliary power source in the figure), a first AC auxiliary power supply (shown as AC1 auxiliary power source in the figure), a second AC auxiliary power supply (shown as AC2 auxiliary power source in the figure), a rectifier unit, a first controllable switch (shown as K1 in the figure), and a second controllable switch (shown as K2 in the figure).

[0024] The input terminal of the rectifier unit is connected to the AC power grid through the first controllable switch, the output terminal of the rectifier unit is connected to the input terminal of the first AC auxiliary power supply and one end of the second controllable switch, and the other end of the second controllable switch is connected to the input terminal of the second AC auxiliary power supply.

[0025] The input terminal of the DC auxiliary power supply is connected to the photovoltaic string, for example, through a BOOST circuit. The output terminals of the DC auxiliary power supply, the first AC auxiliary power supply, and the second AC auxiliary power supply are used to provide power to the load. The power supply voltages that the output terminals of the DC auxiliary power supply, the first AC auxiliary power supply, and the second AC auxiliary power supply can provide include, but are not limited to, 15V, 12V, 10V, 5V, etc., as shown in the figure. The load includes, but is not limited to, the fan, drive unit, sampling unit, control unit, communication unit, PLC, etc., as shown in the figure. Other circuits, such as the BUCK circuit, diodes, etc., can also be connected between the load and the output terminals of the DC auxiliary power supply, the first AC auxiliary power supply, or the second AC auxiliary power supply.

[0026] The control terminals of the first and second controllable switches are used to receive control signals, so as to turn on or off under the action of the control signals.

[0027] In some examples, a photovoltaic string may include one or more photovoltaic panels, each of which consists of multiple photovoltaic cells.

[0028] In some examples, the first controllable switch or the second controllable switch includes a thyristor.

[0029] In some examples, the auxiliary power system further includes a first execution unit and a second execution unit, wherein the first execution unit is used to generate a control signal for the first controllable switch, and the second execution unit is used to generate a control signal for the second controllable switch.

[0030] like Figure 2 As shown, the first execution unit generates the control signal S4 of the first controllable switch based on the first detection signal S1, the second detection signal S2, the selection signal S3, and the wake-up signal.

[0031] Specifically, the first execution unit includes diodes D10-D13, a driver chip, switching transistors Q7-Q9, resistors R13-R15, and capacitor C7. The cathode of diode D10 receives the first detection signal S1, the cathode of diode D11 receives the second detection signal S2, the cathode of diode D12 receives the selection signal S3, and the anode of diode D13 receives the wake-up signal. The anodes of diodes D10, D11, D12, and D13, along with one end of resistor R13, are connected together and connected to the base of switching transistor Q9 (e.g., a transistor). The other end of resistor R13 is connected to the pull-up power supply VCC_3.3V. The collector of switching transistor Q9 (e.g., a transistor) is connected to the power supply VCC_D15V. The emitter of switching transistor Q9 (e.g., a transistor) is connected to one end of the driver chip. The other end of the driver chip, the bases of switching transistors Q7 (e.g., a transistor) and Q8 (e.g., a transistor), and one end of resistor R14 are connected together. The collector of switching transistor Q7 (e.g., a transistor) is connected to the power supply VCC_D15V. The emitter of switching transistor Q7 (e.g., a transistor) is connected to the emitter of switching transistor Q8 (e.g., a transistor). The collector of switching transistor Q8 (e.g., a transistor) is grounded. The other end of resistor R14 outputs the control signal S4 of the first controllable switch through capacitor C7 and resistor R15.

[0032] like Figure 3 As shown, the second execution unit generates the control signal S5 for the second controllable switch based on the selection signal S3 and the wake-up signal.

[0033] Specifically, the second execution unit includes diode D20, a driver chip, switching transistors Q10-Q12, resistors R16-R19, and capacitor C8. Resistor R16 and resistor R17 form a voltage divider circuit. One end of the voltage divider circuit receives the selection signal S3, and the other end is grounded. The anode of diode D20 receives the wake-up signal. The output of the voltage divider circuit is connected to the cathode of diode D20 and to the base of switching transistor Q11 (e.g., a transistor). The collector of switching transistor Q11 is connected to power supply VCC_D15V. The emitter of switching transistor Q11 is connected to one end of the driver chip. The other end of the driver chip, the base of switching transistor Q12 (e.g., a transistor), the base of switching transistor Q10 (e.g., a transistor), and one end of resistor R18 are connected. The collector of switching transistor Q12 is connected to power supply VCC_D15V. The emitter of switching transistor Q12 is connected to the emitter of switching transistor Q10 (e.g., a transistor). The collector of switching transistor Q10 (e.g., a transistor) is grounded. The other end of resistor R18 outputs the control signal S5 of the second controllable switch through capacitor C8 and resistor R19.

[0034] In some examples, the auxiliary power system further includes a first detection unit for detecting the voltage of the AC power grid to output the first detection signal.

[0035] The first detection unit includes a first voltage comparator and a first pull-up circuit. The non-inverting input of the first voltage comparator is connected to the AC power grid, the inverting input of the first voltage comparator is connected to a first threshold voltage, one end of the first pull-up circuit is connected to the output of the first voltage comparator, and the other end of the first pull-up circuit is connected to a first pull-up power supply.

[0036] In a further implementation, the first detection unit also includes a first anti-reverse circuit, one end of which is connected to one end of the first pull-up circuit and the output of the first voltage comparator, and the other end of which is used to output the first detection signal.

[0037] Specifically, such as Figure 4 As shown, the non-inverting input terminal of the first voltage comparator U1 is connected to the AC power grid through resistor R4. A filter capacitor C2 is also connected between resistor R4 and the AC power grid. That is, one end of the filter capacitor C2 is connected between resistor R4 and the AC power grid, and the other end of the filter capacitor C2 is grounded.

[0038] The inverting input of the first voltage comparator U1 is connected to the first threshold voltage. The AC mains voltage is divided by a voltage divider circuit and then connected to the inverting input of the first voltage comparator U1 through a resistor R3. The voltage divider circuit includes resistors R1 and R2 connected in series, capacitor C1 connected in parallel with resistor R2, one end of capacitor C3 connected between resistor R3 and the inverting input of the first voltage comparator U1, and the other end of filter capacitor C3 grounded.

[0039] The non-inverting input terminal and the output terminal of the first voltage comparator U1 are connected by diodes D1 and D2 and resistor R5.

[0040] Resistor R6 forms the first pull-up circuit, and diode D3 forms the first reverse protection circuit. One end of resistor R6 is connected between the output of the first voltage comparator U1 and the anode of diode D3, and the other end of resistor R6 is connected to the first pull-up power supply (e.g., 3.3V in the figure). The cathode of diode D3 outputs the first detection signal S1.

[0041] In some examples, the auxiliary power system further includes a second detection unit for detecting the output voltage of the photovoltaic string to output a second detection signal.

[0042] The second detection unit includes a second voltage comparator and a second pull-up circuit. The non-inverting input of the second voltage comparator is connected to the output voltage of the photovoltaic string, and the inverting input of the second voltage comparator is connected to a second threshold voltage. One end of the second pull-up circuit is connected to the output of the second voltage comparator, and the other end of the second pull-up circuit is connected to a second pull-up power supply.

[0043] In a further implementation, the second detection unit also includes a second anti-reverse circuit, one end of which is connected to one end of the second pull-up circuit and the output of the second voltage comparator, and the other end of which is used to output the second detection signal.

[0044] Specifically, such as Figure 5 As shown, the non-inverting input of the second voltage comparator U2 is connected to the photovoltaic string through resistor R10. A filter capacitor C5 is also connected between resistor R10 and the photovoltaic string. That is, one end of the filter capacitor C5 is connected between resistor R10 and the photovoltaic string, and the other end of the filter capacitor C5 is grounded.

[0045] The inverting input of the second voltage comparator U2 is connected to the second threshold voltage. The AC mains voltage is divided by a voltage divider circuit and then connected to the inverting input of the second voltage comparator U2 through a resistor R9. The voltage divider circuit includes resistors R7 and R8 connected in series, capacitor C4 connected in parallel with resistor R8, one end of capacitor C6 connected between resistor R9 and the inverting input of the second voltage comparator U2, and the other end of filter capacitor C6 grounded.

[0046] The non-inverting input and output terminals of the second voltage comparator U2 are connected by diodes D4 and D5 and resistor R11.

[0047] Resistor R12 forms the second pull-up circuit, and diode D6 forms the second reverse protection circuit. One end of resistor R12 is connected between the output of the second voltage comparator U2 and the anode of diode D6, and the other end of resistor R12 is connected to the second pull-up power supply (e.g., 3.3V in the figure). The cathode of diode D6 outputs the second detection signal S2.

[0048] In the above auxiliary power supply system, the first detection unit is used to determine whether there is power in the AC mains. When the AC mains line voltage is greater than 350V, it is considered that the mains is normal. Further judgment is needed on the output of the second detection unit, the wake-up signal and the currently set working mode to turn the AC auxiliary power supply on and off.

[0049] The second detection unit is used to determine whether the output of the photovoltaic module meets the minimum starting voltage of the DC auxiliary power source. When the photovoltaic voltage is greater than 180V (the specific parameter value can be adjusted, and the following is similar), it is determined that it is daytime and the photovoltaic can generate electricity normally, and all AC auxiliary power sources can be turned on. When the output voltage is less than 100V, it is determined that it is nighttime, and it is necessary to further determine whether to turn on or off the AC auxiliary power source based on whether there is a wake-up signal at the current time.

[0050] The wake-up unit is controlled by software. The wake-up signals include photovoltaic voltage greater than 180V, grid-connected operation requirements, SVG, and PID requirements. When the system detects these signals, it outputs a high level of 3.3V; otherwise, it outputs a low level.

[0051] The mode selection unit is divided into Mode 0, Mode 1, and Mode 2, with software-controlled output. When the user selects Mode 0, auxiliary sources AC1 and AC2 are turned off. When the user selects Mode 1, auxiliary source AC1 is turned on and auxiliary source AC2 is turned off. When the user selects Mode 2, auxiliary sources AC1 and AC2 are turned on.

[0052] The first execution unit receives output signals from the first detection unit, the second detection unit, and the mode selection unit. When all three are high, the transistor in the first execution unit is turned on, the driver chip is powered on, the thyristor on the AC side is turned on, and the AC auxiliary power supply is powered on. When the AC auxiliary power supply voltage is greater than the start-up voltage, the AC auxiliary power supply operates normally. When any one of the three is low, the transistor in the first execution unit is turned off, the driver chip is powered down, the thyristor on the AC side is turned off, and the AC auxiliary power supply stops working.

[0053] The second execution unit receives the output signal from the mode selection unit. When the user selects mode 2, after voltage division by resistors, the transistor in the second execution unit turns on, the driver chip is powered on, and the thyristor controlling the AC auxiliary power source AC2 turns on. When the AC auxiliary power source voltage is greater than the starting voltage, the AC auxiliary power source AC2 operates normally. When the user selects modes 0 and 1, after voltage division by resistors, the transistor in the second execution unit turns off, the driver chip is powered down, the thyristor controlling the AC auxiliary power source AC2 turns off, and the AC auxiliary power source AC2 stops working.

[0054] Based on the user's operating environment, three auxiliary power supply operating modes are defined above. When the user does not need to use the inverter at night, selecting mode 0 will completely shut down the AC auxiliary power supply, and the inverter will not work at night, with zero power consumption. When the user needs to frequently check the inverter status at night, mode 1 can be selected to turn on one AC auxiliary power supply to power the communication unit and control unit, etc. In this mode, the inverter is in standby mode, and the user can use the backend to query the inverter's current status and parameters. When the user needs to frequently start the inverter at night, mode 2 can be selected to turn on all AC auxiliary power supplies. In this mode, the inverter can realize functions such as SVG and PID grid connection at night.

[0055] The following combination Figure 6 The working principle of the auxiliary power supply system is explained below:

[0056] The first detection unit detects the output voltage of the AC power grid. When the line voltage of the AC power grid is less than 300V, the first voltage comparator U1 outputs a low level, the diode D3 is cut off, and the first detection signal S1 is low. When the line voltage of the AC power grid is greater than 350V, the AC power grid is determined to be normal. The output of the first voltage comparator U1 is pulled up by 3.3V and becomes high, and the first detection signal S1 is high.

[0057] When the AC power grid is normal, the second detection unit detects the photovoltaic output voltage. When the photovoltaic voltage gradually decreases and is less than 100V, the output voltage of the second voltage comparator U2 is pulled up by 3.3V to a high level, the diode D6 is turned on, and the output second detection signal S2 is high. When the photovoltaic voltage gradually increases and is greater than 180V, the output of the second voltage comparator U2 is low, the diode D6 is turned off, and the output second detection signal S2 is low.

[0058] When the AC power grid is normal and it is nighttime, the system checks for a wake-up signal. When a wake-up signal is present, the software outputs a high level of 3.3V. At this time, diode D13 connected to the wake-up signal conducts, transistor Q9 conducts, the driver chip is powered on, and the thyristor on the AC side is turned on. When the AC auxiliary power supply voltage is greater than the starting voltage, the AC auxiliary power supply begins to work normally.

[0059] When the AC power grid is normal, it is nighttime, and there is no wake-up signal, the system enters the mode selection state. When mode 0 is selected, the software outputs a low level, such as 0V. Transistor Q9, connected to the driver chip in the first execution unit, is turned off, the AC-side thyristor is turned off, the AC auxiliary power supply is powered down, and the AC auxiliary power supply stops working. When mode 1 is selected, the output is a high level, such as 3.3V. Transistor Q9, connected to the driver chip, is turned on. At this time, the AC-side thyristor is turned on, the AC auxiliary power supply is powered, and AC auxiliary power supply AC1 starts working.

[0060] When mode selection is 0 or mode 1, after voltage division by resistors, transistor Q11 of the second execution unit is turned off, the driver chip is powered down, the control signal S5 controlling AC auxiliary power supply AC2 is at a low level, the thyristor of AC auxiliary power supply AC2 is turned off, and AC auxiliary power supply AC2 stops working. When mode 2 is selected, after voltage division by resistors, transistor Q11 is turned on, the driver chip is powered on, the thyristor of AC auxiliary power supply AC2 is closed, and AC auxiliary power supply AC2 is powered on. When the voltage is greater than the starting voltage, AC auxiliary power supply AC2 starts to work normally.

[0061] The specific work process is as follows:

[0062] During the day, the photovoltaic output voltage gradually increases. When the photovoltaic voltage exceeds 180V, the wake-up unit starts working and outputs a high level, such as 3.3V. Diode D13 of the first execution unit conducts, and transistor Q9 at the power supply terminal of the driver chip conducts, enabling the driver chip to start working. The drive signal passes through the push-pull circuit (Q7, Q8) and controls the thyristor K1 on the AC side to conduct, energizing the AC auxiliary power source AC1. When the voltage exceeds the starting voltage, AC auxiliary power source AC1 starts working. Upon receiving the wake-up signal, diode D20 of the second execution unit conducts, and transistor Q11 at the power supply terminal of the driver chip conducts, enabling the driver chip to start working. The drive signal passes through the push-pull circuit (Q12, Q10) and controls the thyristor K2 on the AC side to conduct, energizing the AC auxiliary power source AC2. When the voltage exceeds the starting voltage, AC auxiliary power source AC2 starts working.

[0063] As the photovoltaic voltage gradually decreases, the second detection unit starts working. When the photovoltaic voltage is less than 100V, the output of the second voltage comparator U2 is pulled up to 3.3V through a pull-up resistor, resulting in a high-level output.

[0064] When the user selects working mode 0 and the AC mains voltage is greater than 350V, the first execution unit starts to work. At this time, the transistor Q9 of the first execution unit is turned off, the driver chip is powered down, the thyristor K1 on the AC side is turned off, and the AC auxiliary power supply AC1 and AC auxiliary power supply AC2 are turned off.

[0065] When the user selects operating mode 1, the AC mains voltage is greater than 350V, and the first execution unit starts working. At this time, transistor Q9 of the first execution unit is turned on, the driver chip is powered on, and the thyristor K1 on the AC side is turned on, at which point the AC auxiliary power supply AC1 starts working. Transistor Q11 of the second execution unit is in the off state at this time, the driver chip is powered off, the thyristor K2 on the AC side is turned off, at which point the AC auxiliary power supply AC2 is turned off.

[0066] When the user selects operating mode 2, the AC mains voltage is greater than 350V. The first execution unit starts working, at which time transistor Q9 of the first execution unit is turned on, the driver chip is powered, and the thyristor K1 on the AC side is turned on, and the AC auxiliary power source AC1 starts working. Transistor Q11 of the second execution unit is turned on at this time, the driver chip is powered, and the thyristor K2 on the AC side is turned on, and the AC auxiliary power source AC2 starts working.

[0067] The preferred embodiments of this application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and spirit of this application shall be within the scope of the claims.

Claims

1. An auxiliary power supply system for a photovoltaic inverter, characterized in that, The auxiliary power supply system includes a DC auxiliary power supply, a first AC auxiliary power supply, a second AC auxiliary power supply, a rectifier unit, a first controllable switch, and a second controllable switch; The input terminal of the rectifier unit is connected to the AC power grid through the first controllable switch, the output terminal of the rectifier unit is connected to the input terminal of the first AC auxiliary power supply and one end of the second controllable switch, and the other end of the second controllable switch is connected to the input terminal of the second AC auxiliary power supply. The input terminal of the DC auxiliary power supply is connected to the photovoltaic string, and the output terminals of the DC auxiliary power supply, the first AC auxiliary power supply, and the second AC auxiliary power supply are used to provide power to the load. The control terminals of the first and second controllable switches are used to receive control signals, so as to turn on or off under the action of the control signals.

2. The auxiliary power supply system according to claim 1, characterized in that, The auxiliary power system further includes a first execution unit and a second execution unit, wherein the first execution unit is used to generate a control signal for the first controllable switch, and the second execution unit is used to generate a control signal for the second controllable switch.

3. The auxiliary power supply system according to claim 2, characterized in that, The first execution unit generates a control signal for the first controllable switch based on the first detection signal, the second detection signal, the selection signal, and the wake-up signal; the second execution unit generates a control signal for the second controllable switch based on the selection signal and the wake-up signal.

4. The auxiliary power supply system according to claim 3, characterized in that, The auxiliary power supply system further includes a first detection unit, which is used to detect the voltage of the AC power grid and output the first detection signal.

5. The auxiliary power supply system according to claim 4, characterized in that, The first detection unit includes a first voltage comparator and a first pull-up circuit. The non-inverting input of the first voltage comparator is connected to the AC power grid, the inverting input of the first voltage comparator is connected to a first threshold voltage, one end of the first pull-up circuit is connected to the output of the first voltage comparator, and the other end of the first pull-up circuit is connected to a first pull-up power supply.

6. The auxiliary power supply system according to claim 5, characterized in that, The first detection unit further includes a first anti-reverse circuit, one end of which is connected to one end of the first pull-up circuit and the output of the first voltage comparator, and the other end of which is used to output the first detection signal.

7. The auxiliary power supply system according to claim 3, characterized in that, The auxiliary power system further includes a second detection unit, which is used to detect the output voltage of the photovoltaic string and output a second detection signal.

8. The auxiliary power supply system according to claim 7, characterized in that, The second detection unit includes a second voltage comparator and a second pull-up circuit. The non-inverting input of the second voltage comparator is connected to the output voltage of the photovoltaic string, and the inverting input of the second voltage comparator is connected to a second threshold voltage. One end of the second pull-up circuit is connected to the output of the second voltage comparator, and the other end of the second pull-up circuit is connected to a second pull-up power supply.

9. The auxiliary power supply system according to claim 8, characterized in that, The second detection unit further includes a second anti-reverse circuit. One end of the second anti-reverse circuit is connected to one end of the second pull-up circuit and the output terminal of the second voltage comparator. The other end of the second anti-reverse circuit is used to output the second detection signal.

10. The auxiliary power supply system according to claim 1, characterized in that, The first controllable switch or the second controllable switch includes a thyristor.

Images