Grid-connected and off-grid switching device and photovoltaic power generation system

Abstract

The embodiment of the invention discloses a grid-connected and off-grid switching device and a photovoltaic power generation system, relates to the technical field of energy, and solves the problem of how to reduce output open-loop voltage fluctuation of an open-loop output end of a DC-DC power conversion circuit. An emitting electrode or a source electrode of the first switch tube is connected with a positive output end of the DC-DC power conversion circuit, a base electrode or a grid electrode of the first switch tube is connected with a collector electrode or a drain electrode of the second switch tube, and an emitting electrode or a source electrode of the second switch tube and an emitting electrode or a source electrode of the third switch tube are connected with one end of the first resistor. The other end of the first resistor is connected with the negative output end of the DC-DC power conversion circuit, the collector electrode or the drain electrode of the third switch tube is connected with the collector electrode or the drain electrode of the first switch tube, and the second resistor and the third resistor which are connected in series are connected between the collector electrode or the drain electrode of the third switch tube and the negative output end of the DC-DC power conversion circuit. The connection point of the second resistor and the third resistor is connected with the base electrode or the grid electrode of the third switch tube.

Description

Technical Field

[0001] The present application relates to the field of energy technology, and in particular to an on-grid and off-grid switching device and a photovoltaic power generation system. Background Art

[0002] The photovoltaic power generation system includes a photovoltaic inverter and an on-grid and off-grid switching device, which can also be called a whole-house backup box. The input end of the photovoltaic inverter is used to connect to the output end of the photovoltaic array, the output end of the photovoltaic inverter is connected to the inverter port of the on-grid and off-grid switching device, the load port of the on-grid and off-grid switching device is used to connect to the load, and the grid port of the on-grid and off-grid switching device is used to connect to the grid.

[0003] Specifically, the on-grid and off-grid switching device includes two switches connected in series, the two switches are connected between the inverter port and the grid port, and the connection point of the two switches is connected to the load port. The on-grid and off-grid switching device also includes a rectifier circuit and a direct current to direct current (DC-DC) power conversion circuit, the input end of the rectifier circuit is connected to the inverter port, the output end of the rectifier circuit is connected to the input end of the DC-DC power conversion circuit, and the open-loop output end of the DC-DC power conversion circuit is connected to the load in the on-grid and off-grid switching device to provide power to the load.

[0004] However, on the one hand, when the power of the load connected to the open-loop output terminal in the on-grid switching device fluctuates, the fluctuation of the open-loop voltage outputted by the open-loop output terminal of the DC-DC power conversion circuit will be large. On the other hand, if the DC-DC power conversion circuit also includes a closed-loop output terminal, during the closed-loop voltage adjustment process outputted by the closed-loop output terminal, the fluctuation of the open-loop voltage outputted by the open-loop output terminal will be large due to the cross-regulation rate. When the fluctuation of the open-loop voltage outputted by the open-loop output terminal of the DC-DC power conversion circuit is large, the power supply demand of the load connected to the open-loop output terminal in the on-grid switching device will not be met, and even the load will be damaged. Therefore, how to reduce the fluctuation of the open-loop voltage outputted by the open-loop output terminal of the DC-DC power conversion circuit has become a problem that needs to be solved urgently. Summary of the invention

[0005] The embodiments of the present application provide an on-grid and off-grid switching device and a photovoltaic power generation system, which solve the problem of how to reduce the fluctuation of the open-loop voltage outputted from the open-loop output end of the DC-DC power conversion circuit.

[0006] In order to achieve the above purpose, the embodiment of the present application adopts the following technical solution:

[0007] In a first aspect of an embodiment of the present application, a grid-connected and off-grid switching device is provided, the grid-connected and off-grid switching device comprising: a first switch and a second switch connected in series, the first switch and the second switch are connected between an inverter port and a grid port of the grid-connected and off-grid switching device, and a connection point between the first switch and the second switch is connected to a load port of the grid-connected and off-grid switching device. A rectifier circuit, a capacitor and a DC-DC power conversion circuit, the input end of the rectifier circuit is connected to the inverter port, the output end of the rectifier circuit is connected to the input end of the DC-DC power conversion circuit, the output end of the rectifier circuit comprises a positive output end and a negative output end, and the capacitor is connected between the positive output end and the negative output end of the rectifier circuit. The first switch tube, the second switch tube, the third switch tube and the first resistor, the open-loop output end of the DC-DC power conversion circuit includes a positive output end and a negative output end, the emitter or source of the first switch tube is connected to the positive output end of the DC-DC power conversion circuit, the base or gate of the first switch tube is connected to the collector or drain of the second switch tube, the base or gate of the second switch tube is used to receive a reference voltage, the emitter or source of the second switch tube and the emitter or source of the third switch tube are connected to one end of the first resistor, the other end of the first resistor is connected to the negative output end of the DC-DC power conversion circuit, and the collector or drain of the third switch tube is connected to the collector or drain of the first switch tube. The second resistor and the third resistor are connected in series, the second resistor and the third resistor are connected between the collector or drain of the third switch tube and the negative output end of the DC-DC power conversion circuit, the connection point of the second resistor and the third resistor is connected to the base or gate of the third switch tube, and the collector or drain of the third switch tube and the negative output end of the DC-DC power conversion circuit are connected to the load in the on-grid switching device. The first switch tube is a PNP transistor, PMOS or PIGBT, and the second switch tube and the third switch tube are NPN transistors, NMOS or NIGBT.

[0008] Based on the present solution, the step-down circuit is realized by using the first switch tube to the third switch tube and the first resistor to the third resistor. When the power fluctuation of the load in the on-grid switching device causes the open-loop voltage outputted from the open-loop output end of the DC-DC power conversion circuit to fluctuate by more than the voltage threshold, due to the voltage dividing effect of the first resistor to the third resistor, the third switch tube satisfies the on-condition and will be turned on. After the third switch tube is turned on, the second switch tube satisfies the off-condition and will be turned off. After the second switch tube is turned off, the first switch tube satisfies the off-condition and will be turned off. The DC-DC power conversion circuit will stop supplying power to the load, thereby reducing the open-loop voltage provided by the open-loop output end of the DC-DC power conversion circuit to the load. Therefore, the fluctuation of the open-loop voltage can be reduced. Moreover, there is no need for a controller to control the first switch tube to the third switch tube. The topology is simpler and the cost is lower. When the first switch tube to the third switch tube are triodes, the triodes do not need to work in the linear amplification region. The power consumption is lower and the reliability is higher.

[0009] In combination with the first aspect, in one embodiment, the on-grid and off-grid switching device further includes a controller, and the DC-DC power conversion circuit further includes a closed-loop output terminal. The controller is used to obtain a voltage or current at the closed-loop output terminal and output a pulse width modulation signal, the voltage or current at the closed-loop output terminal is used to determine a duty cycle of the pulse width modulation signal, and the pulse width modulation signal is used to control a switch tube in the DC-DC power conversion circuit.

[0010] Based on this solution, the step-down circuit is realized by using the first switch tube to the third switch tube and the first resistor to the third resistor. In the process of adjusting the closed-loop voltage outputted from the closed-loop output end, when the open-loop voltage outputted from the open-loop output end fluctuates greatly due to the cross-adjustment, the first switch tube is turned off, and the DC-DC power conversion circuit stops supplying power to the load, thereby reducing the open-loop voltage provided by the open-loop output end of the DC-DC power conversion circuit to the load, thereby reducing the fluctuation of the open-loop voltage, and the topology is simpler, the cost is lower, the power consumption is lower, and the reliability is higher.

[0011] In combination with the first aspect, in one embodiment, the on-grid and off-grid switching device also includes a reference voltage source, the positive electrode of the reference voltage source is connected to the positive output terminal of the DC-DC power conversion circuit, the negative electrode of the reference voltage source is connected to the negative output terminal of the DC-DC power conversion circuit, and the output terminal of the reference voltage source is connected to the base or gate of the second switching tube.

[0012] Based on this solution, a reference voltage is provided by a reference voltage source, so that a stable reference voltage can be provided, and the stability and reliability of the on-grid and off-grid switching device can be improved.

[0013] In combination with the first aspect, in one embodiment, the reference voltage source includes a Zener diode and a fourth resistor and a fifth resistor connected in series, the fourth resistor and the fifth resistor are connected between the positive electrode of the reference voltage source and the negative electrode of the reference voltage source, the connection point of the fourth resistor and the fifth resistor is connected to the cathode of the Zener diode, the anode of the Zener diode is connected to the negative electrode of the reference voltage source, and the cathode of the Zener diode is also connected to the output end of the reference voltage source.

[0014] Based on this scheme, compared with other methods of realizing the reference voltage source, the reference voltage source is realized by using a Zener diode, the circuit topology is simpler and the cost is lower, and the Zener diode has good stability, thereby reducing the circuit topology complexity and cost of the on-grid and off-grid switching device and improving reliability.

[0015] In combination with the first aspect, in one implementation, the DC-DC power conversion circuit is a flyback DC-DC power conversion circuit.

[0016] Based on this solution, since the flyback DC-DC power conversion circuit has the advantages of current isolation and high safety, the reliability and safety of the on-grid and off-grid switching device can be improved.

[0017] In combination with the first aspect, in one embodiment, when the voltage across the second resistor and the third resistor is greater than the voltage threshold, the voltage at the connection point of the second resistor and the third resistor is greater than the reference voltage, the third switch tube is turned on, the second switch tube is turned off, and the first switch tube is turned off.

[0018] Based on this solution, when the open-loop voltage outputted from the open-loop output terminal of the DC-DC power conversion circuit fluctuates, the first switch is turned off, and the DC-DC power conversion circuit stops supplying power to the load, thereby reducing the open-loop voltage provided to the load by the open-loop output terminal of the DC-DC power conversion circuit. Therefore, the fluctuation of the open-loop voltage can be reduced, load damage in the on-grid and off-grid switching device can be avoided, and the reliability of the on-grid and off-grid switching device can be improved.

[0019] In combination with the first aspect, in one embodiment, when the voltage across the second resistor and the third resistor is less than or equal to the voltage threshold, the voltage at the connection point of the second resistor and the third resistor is less than or equal to the reference voltage, the third switch tube is turned off, the second switch tube is turned on, and the first switch tube is turned on.

[0020] Based on this solution, when the open-loop voltage outputted from the open-loop output terminal of the DC-DC power conversion circuit does not fluctuate, the first switch tube is turned on, thereby providing power to the load in the on-grid and off-grid switching device.

[0021] The second aspect of the embodiment of the present application provides a photovoltaic power generation system, which includes a photovoltaic inverter and an on-grid switching device, wherein the input end of the photovoltaic inverter is used to connect to the output end of the photovoltaic array, the output end of the photovoltaic inverter is connected to the inverter port of the on-grid switching device, the grid port of the on-grid switching device is used to connect to the grid, and the load port of the on-grid switching device is used to connect to the load. The on-grid switching device includes: a first switch and a second switch connected in series, the first switch and the second switch are connected between the inverter port and the grid port, and the connection point of the first switch and the second switch is connected to the load port. A rectifier circuit, a capacitor and a DC-DC power conversion circuit, the input end of the rectifier circuit is connected to the inverter port, the output end of the rectifier circuit is connected to the input end of the DC-DC power conversion circuit, the output end of the rectifier circuit includes a positive output end and a negative output end, and the capacitor is connected between the positive output end and the negative output end of the rectifier circuit. The first switch tube, the second switch tube, the third switch tube and the first resistor, the open-loop output end of the DC-DC power conversion circuit includes a positive output end and a negative output end, the emitter or source of the first switch tube is connected to the positive output end of the DC-DC power conversion circuit, the base or gate of the first switch tube is connected to the collector or drain of the second switch tube, the base or gate of the second switch tube is used to receive a reference voltage, the emitter or source of the second switch tube and the emitter or source of the third switch tube are connected to one end of the first resistor, the other end of the first resistor is connected to the negative output end of the DC-DC power conversion circuit, and the collector or drain of the third switch tube is connected to the collector or drain of the first switch tube. The second resistor and the third resistor are connected in series, the second resistor and the third resistor are connected between the collector or drain of the third switch tube and the negative output end of the DC-DC power conversion circuit, the connection point of the second resistor and the third resistor is connected to the base or gate of the third switch tube, and the collector or drain of the third switch tube and the negative output end of the DC-DC power conversion circuit are connected to the load in the on-grid switching device. The first switch tube is a PNP transistor, PMOS or PIGBT, and the second switch tube and the third switch tube are NPN transistors, NMOS or NIGBT.

[0022] In combination with the second aspect, in one embodiment, the on-grid and off-grid switching device further includes a controller, and the DC-DC power conversion circuit further includes a closed-loop output terminal. The controller is used to obtain the voltage or current of the closed-loop output terminal and output a pulse width modulation signal, the voltage or current of the closed-loop output terminal is used to determine the duty cycle of the pulse width modulation signal, and the pulse width modulation signal is used to control the switch tube in the DC-DC power conversion circuit.

[0023] In combination with the second aspect, in one embodiment, the on-grid and off-grid switching device also includes a reference voltage source, the positive electrode of the reference voltage source is connected to the positive output terminal of the DC-DC power conversion circuit, the negative electrode of the reference voltage source is connected to the negative output terminal of the DC-DC power conversion circuit, and the output terminal of the reference voltage source is connected to the base or gate of the second switching tube.

[0024] In combination with the second aspect, in one embodiment, the reference voltage source includes a Zener diode and a fourth resistor and a fifth resistor connected in series, the fourth resistor and the fifth resistor are connected between the positive electrode of the reference voltage source and the negative electrode of the reference voltage source, the connection point of the fourth resistor and the fifth resistor is connected to the cathode of the Zener diode, the anode of the Zener diode is connected to the negative electrode of the reference voltage source, and the cathode of the Zener diode is also connected to the output end of the reference voltage source.

[0025] In combination with the second aspect, in one implementation, the DC-DC power conversion circuit is a flyback DC-DC power conversion circuit.

[0026] In combination with the second aspect, in one embodiment, when the voltage across the second resistor and the third resistor is greater than the voltage threshold, the voltage at the connection point of the second resistor and the third resistor is greater than the reference voltage, the third switch tube is turned on, the second switch tube is turned off, and the first switch tube is turned off.

[0027] In combination with the second aspect, in one embodiment, when the voltage across the second resistor and the third resistor is less than or equal to the voltage threshold, the voltage at the connection point of the second resistor and the third resistor is less than or equal to the reference voltage, the third switch tube is turned off, the second switch tube is turned on, and the first switch tube is turned on.

[0028] The description of the second aspect in this application can refer to the detailed description of the first aspect; and the beneficial effects of the second aspect can refer to the analysis of the beneficial effects of the first aspect, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of a circuit topology of a photovoltaic power generation system;

[0030] Figure 2 A schematic diagram of an application scenario of an on-grid and off-grid switching device provided in an embodiment of the present application;

[0031] Figure 3 A schematic diagram of a circuit topology of an on-grid and off-grid switching device provided in an embodiment of the present application;

[0032] Figure 4 A schematic diagram of a circuit topology of another on-grid and off-grid switching device provided in an embodiment of the present application;

[0033] Figure 5A circuit topology diagram of another on-grid and off-grid switching device provided in an embodiment of the present application;

[0034] Figure 6 A circuit topology diagram of another on-grid and off-grid switching device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] The following will discuss the making and use of each embodiment in detail. However, it should be understood that many applicable inventive concepts provided by this application can be implemented in a variety of specific environments. The specific embodiments discussed are only used to illustrate the specific ways to implement and use this description and this technology, and do not limit the scope of this application.

[0036] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.

[0037] Various circuits or other components may be described or referred to as being "configured to" perform one or more tasks. In this case, "configured to" is used to imply structure by indicating that the circuit / component includes structure (e.g., circuitry) that performs the one or more tasks during operation. Thus, even when the specified circuit / component is not currently operational (e.g., not turned on), the circuit / component may be referred to as being configured to perform the task. Circuits / components used with the phrase "configured to" include hardware, such as circuits that perform an operation, etc.

[0038] The technical scheme in the embodiment of the present application will be described below in conjunction with the accompanying drawings in the embodiment of the present application. In the present application, the character " / " generally indicates that the preceding and following associated objects are in an "or" relationship. In the embodiment of the present application, the words "first", "second", etc. do not limit the quantity and order.

[0039] In this application, the words "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the words "exemplary" or "for example" is intended to present the related concepts in a concrete way.

[0040] Before introducing the embodiments of the present application, the background technology involved in the present application is first introduced.

[0041] like Figure 1The figure shows a circuit topology diagram of a photovoltaic power generation system 100. The photovoltaic power generation system 100 includes a photovoltaic inverter 110 and an on-grid switching device 120. The input end of the photovoltaic inverter 110 is used to connect to the output end of the photovoltaic array 200, the output end of the photovoltaic inverter 110 is connected to the inverter port of the on-grid switching device 120, the load port of the on-grid switching device 120 is used to connect to the load 300, and the grid port of the on-grid switching device 120 is used to connect to the grid 400.

[0042] Specifically, refer to Figure 1 The on-grid switching device 120 includes two switches (a first switch K1 and a second switch K2) connected in series, the two switches are connected between the inverter port and the grid port, and the connection point of the two switches is connected to the load port. The on-grid switching device 120 also includes a rectifier circuit 121, a DC-DC power conversion circuit 122, and a first capacitor C1 and a second capacitor C2 connected in series. The input end of the rectifier circuit 121 is connected to the inverter port, the output end of the rectifier circuit 121 is connected to the input end of the DC-DC power conversion circuit 122, and the open-loop output end of the DC-DC power conversion circuit 122 is connected to the load 123 in the on-grid switching device 120 to provide power to the load 123. For example, the load 123 can be a fan of an energy management assistant (EMMA) in the on-grid switching device 120. The output end of the rectifier circuit 121 includes a positive output end and a negative output end. The first capacitor C1 and the second capacitor C2 are connected between the positive output end and the negative output end of the rectifier circuit 121.

[0043] Continue to refer to Figure 1 , when the power of the load 123 in the on-grid switching device 120 fluctuates, the open-loop voltage output from the open-loop output end of the DC-DC power conversion circuit 122 will fluctuate greatly. If the DC-DC power conversion circuit 122 also includes a closed-loop output end, during the closed-loop voltage adjustment process output from the closed-loop output end, the cross-regulation rate will cause the open-loop voltage output from the open-loop output end to fluctuate greatly. Among them, the cross-regulation rate is a concept in a multi-channel output switching power supply, which describes the degree of influence on the output voltage of a certain output circuit when the load of other output circuits changes in a multi-channel output switching power supply. Specifically, the cross-regulation rate is defined as S=ΔV / V×100%, where "S" represents the cross-regulation rate, "ΔV" represents the output voltage change of a certain output circuit, and "V" represents the rated output voltage of a certain output circuit.

[0044] In the case where the open-loop voltage outputted from the open-loop output terminal of the DC-DC power conversion circuit 122 fluctuates greatly, it will not be able to meet the power supply demand of the load 123 in the on-grid switching device 120, and may even damage the load 123. Therefore, how to reduce the fluctuation of the open-loop voltage outputted from the open-loop output terminal of the DC-DC power conversion circuit 122 becomes an urgent problem to be solved.

[0045] In one embodiment, continue to refer to Figure 1 The grid-connected and off-grid switching device 120 may further include a step-down circuit 124, which is connected between the open-loop output terminal of the DC-DC power conversion circuit 122 and the input terminal of the load 123. The step-down circuit 124 is used to reduce the open-loop voltage when the open-loop voltage output from the open-loop output terminal of the DC-DC power conversion circuit 122 is greater than the voltage threshold, thereby reducing the fluctuation of the open-loop voltage output from the open-loop output terminal of the DC-DC power conversion circuit 122, so as to improve the safety and reliability of the grid-connected and off-grid switching device 120.

[0046] In one embodiment, the step-down circuit 124 may adopt a standard step-down conversion circuit (also referred to as a Buck circuit), but the standard step-down conversion circuit requires a controller to control the switch tube, and the topology is complex and the cost is high. Alternatively, the step-down circuit 124 may adopt a linear voltage regulation circuit, but the transistors in the linear voltage regulation circuit work in the linear amplification region for a long time, and the risk of transistor damage is high, which will lead to high power consumption and low reliability of the step-down circuit 124. At the same time, due to the limitation of the voltage Vce between the collector and the emitter of the transistor, the fluctuation of the open-loop voltage is still large, and the power supply demand of the load 123 cannot be met. In summary, when the step-down circuit 124 adopts a standard step-down conversion circuit or a linear voltage regulation circuit to reduce the fluctuation of the open-loop voltage, there are problems such as complex topology, high cost, high power consumption and low reliability.

[0047] Based on this, an embodiment of the present application provides an on-grid and off-grid switching device, in which a switching tube and a resistor are used to implement a step-down circuit, which can reduce the fluctuation of the open-loop voltage outputted from the open-loop output end of the DC-DC power conversion circuit, and does not require a controller to control the switching tube. The topology is simpler and the cost is lower. When the switching tube is a triode, the triode does not need to operate in the linear amplification region, and the power consumption is lower and the reliability is higher.

[0048] In one embodiment, if Figure 2 As shown, the on-grid and off-grid switching device 500 provided in the embodiment of the present application can be used as an independent device.

[0049] In one embodiment, if Figure 2As shown in the figure, it is a schematic diagram of an application scenario of an on-grid / off-grid switching device 500 provided by an embodiment of the present application. This on-grid / off-grid switching device 500 can replace the above-mentioned on-grid / off-grid switching device 120 and be applied to the above-mentioned photovoltaic power generation system 100, which further includes a photovoltaic inverter 110. The input end of the photovoltaic inverter 110 is used to connect to the output end of the photovoltaic array 200, the output end of the photovoltaic inverter 110 is connected to the inverter port of the on-grid / off-grid switching device 500, the load port of the on-grid / off-grid switching device 500 is used to connect to the load 300, and the grid port of the on-grid / off-grid switching device 500 is used to connect to the grid 400. The photovoltaic array 200 is used to convert solar energy into direct current, the photovoltaic inverter 110 is used to convert this direct current into alternating current, and the on-grid / off-grid switching device 500 is used for on-grid / off-grid switching.

[0050] As Figure 3 shown in the figure, it is a schematic circuit topology diagram of an on-grid / off-grid switching device 500 provided by an embodiment of the present application. This on-grid / off-grid switching device 500 includes: a first switch K1 and a second switch K2 connected in series, the first switch K1 and the second switch K2 are connected between the inverter port and the grid port of the on-grid / off-grid switching device 500, and the connection point of the first switch K1 and the second switch K2 is connected to the load port of the on-grid / off-grid switching device 500. A rectifier circuit 510, a capacitor C, and a DC-DC power conversion circuit 520, the input end of the rectifier circuit 510 is connected to the inverter port, the output end of the rectifier circuit 510 is connected to the input end of the DC-DC power conversion circuit 520, the output end of the rectifier circuit 510 includes a positive output end and a negative output end, and the capacitor C is connected between the positive output end and the negative output end of the rectifier circuit 510.

[0051] Referring Figure 3 to the figure, the on-grid / off-grid switching device 500 further includes a first switching transistor Q1, a second switching transistor Q2, a third switching transistor Q3, and a first resistor R1. The open-loop output end of the DC-DC power conversion circuit 520 includes a positive output end and a negative output end. The emitter (E) or source (S) of the first switching transistor Q1 is connected to the positive output end of the DC-DC power conversion circuit 520, the base (B) or gate (G) of the first switching transistor Q1 is connected to the collector (C) or drain (D) of the second switching transistor Q2, the base or gate of the second switching transistor Q2 is used to receive a reference voltage Vref, the emitter or source of the second switching transistor Q2 and the emitter or source of the third switching transistor Q3 are connected to one end of the first resistor R1, the other end of the first resistor R1 is connected to the negative output end of the DC-DC power conversion circuit 520, and the collector or drain of the third switching transistor Q3 is connected to the collector or drain of the first switching transistor Q1. The first resistor R1 is used to protect the third switching transistor Q3 when the third switching transistor Q3 is turned on.

[0052] Continue to refer to Figure 3 The on-grid switching device 500 further includes a second resistor R2 and a third resistor R3 connected in series, the second resistor R2 and the third resistor R3 are connected between the collector or drain of the third switch tube Q3 and the negative output terminal of the DC-DC power conversion circuit 520, and the connection point of the second resistor R2 and the third resistor R3 is connected to the base or gate of the third switch tube Q3. The collector or drain of the third switch tube Q3 and the negative output terminal of the DC-DC power conversion circuit 520 are connected to the load 530 in the on-grid switching device 500 to provide power to the load 530. For example, the load 530 can be a fan of the energy management assistant EMMA in the on-grid switching device 500. The circuit composed of the above-mentioned rectifier circuit 510, capacitor C, DC-DC power conversion circuit 520, the first switch tube Q1 to the third switch tube Q3, and the first resistor R1 to the third resistor R3 can be called an auxiliary power supply.

[0053] The first switch tube Q1 is a PNP transistor, a P-channel metal-oxide-semiconductor field-effect transistor (PMOS) or a P-channel insulated gate bipolar transistor (PIGBT), and the second switch tube Q2 and the third switch tube Q3 are NPN transistors, NMOS or NIGBT. The embodiment of the present application does not limit the specific types of the first switch tube Q1, the second switch tube Q2 and the third switch tube Q3, and continues to refer to Figure 3 In the embodiment of the present application, the first switch tube Q1 is a PNP transistor, and the second switch tube Q2 and the third switch tube Q3 are NPN transistors for exemplary description.

[0054] In one embodiment, referring to Figure 3, when the voltage across the second resistor R2 and the third resistor R3 is greater than the voltage threshold, the voltage at the connection point of the second resistor R2 and the third resistor R3 is greater than the reference voltage Vref, the voltage at the base of the third switch tube Q3 is greater than the voltage at the emitter, the voltage at the collector is greater than the voltage at the emitter, and there is current at the base, the third switch tube Q3 will be turned on, and the embodiment of the present application does not limit the specific values ​​of the voltage threshold and the reference voltage Vref. The voltage at the base of the second switch tube Q2 is the reference voltage Vref. After the third switch tube Q3 is turned on, the voltage at the emitter of the second switch tube Q2 is the voltage at the positive output end of the DC-DC power conversion circuit 520. The voltage at the emitter of the second switch tube Q2 is greater than the voltage at the base, and the second switch tube Q2 will be turned off. After the second switch tube Q2 is turned off, there is no current at the base of the first switch tube Q1, and the first switch tube Q1 will be turned off. After the first switch tube Q1 is turned off, the voltage output from the collector of the third switch tube Q3 and the negative output end of the DC-DC power conversion circuit 520 to the load 530 will drop. Thus, when the open-loop voltage outputted from the open-loop output terminal of the DC-DC power conversion circuit 520 fluctuates by a voltage greater than the voltage threshold, the fluctuation of the open-loop voltage can be reduced. It can be understood that the circuit composed of the first switch tube Q1 to the third switch tube Q3 and the first resistor R1 to the third resistor R3 can be called a step-down circuit.

[0055] In one implementation, the voltage threshold may be adjusted by selecting a second resistor R2 and a third resistor R3 with different resistance values. The embodiment of the present application does not limit the specific values ​​of the second resistor R2 and the third resistor R3.

[0056] In one embodiment, continue to refer to Figure 3 , when the voltage across the second resistor R2 and the third resistor R3 is less than or equal to the voltage threshold, the voltage at the connection point of the second resistor R2 and the third resistor R3 is less than or equal to the reference voltage Vref, the voltage at the base of the third switch tube Q3 is less than or equal to the voltage at the emitter, and the third switch tube Q3 will be turned off. The voltage at the base of the second switch tube Q2 is the reference voltage Vref. After the third switch tube Q3 is turned off, the voltage at the emitter of the second switch tube Q2 is the voltage at the negative output end of the DC-DC power conversion circuit 520. The voltage at the base of the second switch tube Q2 is greater than the voltage at the emitter, the voltage at the collector is greater than the voltage at the emitter, and there is current at the base, the second switch tube Q2 will be turned on, the voltage at the base of the first switch tube Q1 is greater than the voltage at the emitter, the voltage at the collector is greater than the voltage at the emitter, and there is current at the base, the first switch tube Q1 will be turned on. Thus, the collector of the third switch tube Q3 and the negative output end of the DC-DC power conversion circuit 520 can continuously provide power to the load 530.

[0057] In one implementation, the first switch K1 and the second switch K2 include relays or contactors, and the embodiment of the present application does not limit the specific types of the two switches.

[0058] In one embodiment, when the output end of the photovoltaic inverter 110 outputs single-phase AC power, the above-mentioned rectifier circuit 510 can be a single-phase rectifier circuit. When the output end of the photovoltaic inverter 110 outputs three-phase AC power, the above-mentioned rectifier circuit 510 can be a three-phase rectifier circuit. The embodiment of the present application does not limit this.

[0059] In one embodiment, the type of the above-mentioned DC-DC power conversion circuit 520 includes isolated type, non-isolated type, buck type or boost type, and the isolated DC-DC power conversion circuit includes a flyback DC-DC power conversion circuit. The embodiment of the present application does not limit the specific type of the DC-DC power conversion circuit 520.

[0060] In one embodiment, the DC-DC power conversion circuit 520 is a flyback DC-DC power conversion circuit. Since the flyback DC-DC power conversion circuit has the advantages of current isolation and high safety, the reliability and safety of the on-grid and off-grid switching device 500 can be improved.

[0061] In one embodiment, Figure 4 FIG. 1 is a schematic diagram of a circuit topology of another on-grid and off-grid switching device 500 provided in an embodiment of the present application, which is similar to the above Figure 3 Compared with the circuit topology of the on-grid and off-grid switching device 500 shown in the figure, the difference is that the capacitor C includes a first capacitor C1 and a second capacitor C2 connected in series, so that the withstand voltage value of the capacitor C can be improved, and the reliability of the on-grid and off-grid switching device 500 can be improved.

[0062] In one embodiment, the step-down circuit composed of the first switch tube Q1 to the third switch tube Q3 and the first resistor R1 to the third resistor R3 provided in the embodiment of the present application can also be applied to the auxiliary power supply of equipment such as an optimizer, a photovoltaic inverter or an uninterruptible power supply (UPS) to reduce the fluctuation of the open-loop voltage output by the DC-DC power conversion circuit in the auxiliary power supply. The embodiment of the present application is not limited to this.

[0063] The on-grid switching device 500 provided in the embodiment of the present application adopts the first switch tube Q1 to the third switch tube Q3 and the first resistor R1 to the third resistor R3 to realize the step-down circuit. When the power fluctuation of the load 530 causes the open-loop voltage outputted from the open-loop output end of the DC-DC power conversion circuit 520 to fluctuate greater than the voltage threshold, due to the voltage dividing effect of the first resistor R1 to the third resistor R3, the third switch tube Q3 meets the turn-on condition and will be turned on. After the third switch tube Q3 is turned on, the second switch tube Q2 meets the turn-off condition and will be turned off. After shutdown, the first switch tube Q1 will be shut down when the shutdown condition is met, and the DC-DC power conversion circuit 520 will stop supplying power to the load 530, thereby reducing the open-loop voltage provided by the open-loop output end of the DC-DC power conversion circuit 520 to the load 530, thereby reducing the fluctuation of the open-loop voltage, and there is no need for a controller to control the first switch tube Q1 to the third switch tube Q3, the topology is simpler and the cost is lower, and when the first switch tube Q1 to the third switch tube Q3 are triodes, there is no need for the triodes to operate in the linear amplification region, the power consumption is lower and the reliability is higher.

[0064] In one embodiment, Figure 4 As shown, the on-grid and off-grid switching device 500 further includes a controller 540, and the DC-DC power conversion circuit 520 further includes a closed-loop output terminal. The controller 540 is used to obtain the voltage or current of the closed-loop output terminal and output a pulse width modulation (PWM) signal. The voltage or current of the closed-loop output terminal is used to determine the duty cycle of the pulse width modulation signal. The pulse width modulation signal is used to control the switch tube in the DC-DC power conversion circuit 520.

[0065] In one embodiment, the on-grid and off-grid switching device 500 may also include a voltage detection circuit or a current detection circuit, so that the controller 540 can obtain the voltage or current at the closed-loop output end through the voltage detection circuit or the current detection circuit. For details, please refer to the prior art, and the embodiments of the present application will not be repeated here.

[0066] In one embodiment, since the open-loop output terminal and the closed-loop output terminal of the DC-DC power conversion circuit 520 are reinforced insulation, power is provided to the load 530 through the open-loop output terminal, thereby meeting the safety design specifications. Enhanced insulation refers to a series of measures and designs taken in electrical equipment or systems to improve insulation performance and ensure safe operation of equipment and personnel safety.

[0067] In one embodiment, the DC-DC power conversion circuit 520 may include multiple open-loop output terminals, and the grid-connected and off-grid switching device 500 may also include multiple step-down circuits provided in the embodiments of the present application. The multiple open-loop output terminals are respectively connected one-to-one with the multiple step-down circuits. The embodiments of the present application do not limit the specific number of open-loop output terminals included in the DC-DC power conversion circuit 520, and the specific number of step-down circuits included in the grid-connected and off-grid switching device 500.

[0068] In one implementation, the controller 540 includes a digital signal processing (DSP) chip or a microcontroller unit (MCU), which may also be referred to as a single-chip microcomputer, but the present application does not limit this.

[0069] The on-grid and off-grid switching device 500 provided in the embodiment of the present application adopts the first switch tube Q1 to the third switch tube Q3, and the first resistor R1 to the third resistor R3 to realize the step-down circuit. During the closed-loop voltage outputted from the closed-loop output end is adjusted, when the open-loop voltage outputted from the open-loop output end fluctuates greatly due to the cross-adjustment, the first switch tube Q1 is turned off, and the DC-DC power conversion circuit 520 stops supplying power to the load 530, thereby reducing the open-loop voltage provided by the open-loop output end of the DC-DC power conversion circuit 520 to the load 530, thereby reducing the fluctuation of the open-loop voltage, and the topology is simpler, the cost is lower, the power consumption is lower, and the reliability is higher.

[0070] In one embodiment, Figure 5 As shown, it is a circuit topology diagram of another on-grid and off-grid switching device 500 provided in an embodiment of the present application. The on-grid and off-grid switching device 500 also includes a reference voltage source 550, the positive electrode of the reference voltage source 550 is connected to the positive output terminal of the DC-DC power conversion circuit 520, the negative electrode of the reference voltage source 550 is connected to the negative output terminal of the DC-DC power conversion circuit 520, and the output terminal of the reference voltage source 550 is connected to the base or gate of the second switch tube Q2 to provide the above-mentioned reference voltage Vref.

[0071] In one embodiment, Figure 6As shown, it is a circuit topology diagram of another on-grid switching device 500 provided in an embodiment of the present application. The above-mentioned reference voltage source 550 includes a zener diode (ZD) ZD and a fourth resistor R4 and a fifth resistor R5 connected in series, the fourth resistor R4 and the fifth resistor R5 are connected between the positive electrode of the reference voltage source 550 and the negative electrode of the reference voltage source 550, the connection point of the fourth resistor R4 and the fifth resistor R5 is connected to the cathode of the zener diode ZD, the anode of the zener diode ZD is connected to the negative electrode of the reference voltage source 550, and the cathode of the zener diode ZD is also connected to the output end of the reference voltage source 550. The zener diode ZD can also be called a zener diode, or the reference voltage source 550 can be implemented by using a reference voltage chip, a resistor voltage divider, etc., and the embodiment of the present application does not limit this.

[0072] The on-grid and off-grid switching device 500 provided in the embodiment of the present application uses a Zener diode ZD to implement the reference voltage source 550, compared with other methods of implementing the reference voltage source 550. The circuit topology is simpler and the cost is lower, and the Zener diode ZD has good stability, thereby reducing the circuit topology complexity and cost of the on-grid and off-grid switching device 500 and improving reliability.

[0073] Based on this, Figure 2 As shown, the embodiment of the present application also provides a photovoltaic power generation system 100, which includes a photovoltaic inverter 110 and an on-grid switching device 500, the input end of the photovoltaic inverter 110 is used to connect to the output end of the photovoltaic array 200, the output end of the photovoltaic inverter 110 is connected to the inverter port of the on-grid switching device 500, the grid port of the on-grid switching device 500 is used to connect to the grid 400, and the load port of the on-grid switching device 500 is used to connect to the load 300. The circuit topology of the on-grid switching device 500 is as described above. Figures 2 to 6 The circuit topology of the on-grid and off-grid switching device 500 shown in any of the accompanying drawings.

[0074] The above detailed description of the on-grid and off-grid switching device 500 and the analysis of the beneficial effects can be correspondingly referred to the photovoltaic power generation system 100, and the embodiments of the present application will not be repeated here.

[0075] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application 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 grid-connected and off-grid switching device, characterized in that: The on-grid and off-grid switching device comprises: A first switch and a second switch connected in series, wherein the first switch and the second switch are connected between an inverter port and a grid port of the on-grid and off-grid switching device, and a connection point between the first switch and the second switch is connected to a load port of the on-grid and off-grid switching device; A rectifier circuit, a capacitor and a DC-DC power conversion circuit, wherein the input end of the rectifier circuit is connected to the inverter port, the output end of the rectifier circuit is connected to the input end of the DC-DC power conversion circuit, the output end of the rectifier circuit includes a positive output end and a negative output end, and the capacitor is connected between the positive output end and the negative output end of the rectifier circuit; a first switch tube, a second switch tube, a third switch tube and a first resistor, the open-loop output end of the DC-DC power conversion circuit includes a positive output end and a negative output end, the emitter or source of the first switch tube is connected to the positive output end of the DC-DC power conversion circuit, the base or gate of the first switch tube is connected to the collector or drain of the second switch tube, the base or gate of the second switch tube is used to receive a reference voltage, the emitter or source of the second switch tube and the emitter or source of the third switch tube are connected to one end of the first resistor, the other end of the first resistor is connected to the negative output end of the DC-DC power conversion circuit, and the collector or drain of the third switch tube is connected to the collector or drain of the first switch tube; A second resistor and a third resistor connected in series, wherein the second resistor and the third resistor are connected between the collector or drain of the third switch tube and the negative output end of the DC-DC power conversion circuit, the connection point of the second resistor and the third resistor is connected to the base or gate of the third switch tube, and the collector or drain of the third switch tube and the negative output end of the DC-DC power conversion circuit are connected to the load in the on-grid and off-grid switching device; The first switch tube is a PNP transistor, a PMOS or a PIGBT; The second switch tube and the third switch tube are NPN transistors, NMOS or NIGBT.

2. The on-grid and off-grid switching device according to claim 1, characterized in that: The on-grid and off-grid switching device further includes a controller, and the DC-DC power conversion circuit further includes a closed-loop output terminal; The controller is used to obtain the voltage or current at the closed-loop output end and output a pulse width modulation signal. The voltage or current at the closed-loop output end is used to determine the duty cycle of the pulse width modulation signal. The pulse width modulation signal is used to control the switch tube in the DC-DC power conversion circuit.

3. The on-grid and off-grid switching device according to claim 1 or 2, characterized in that: The on-grid and off-grid switching device also includes a reference voltage source, the positive electrode of the reference voltage source is connected to the positive output end of the DC-DC power conversion circuit, the negative electrode of the reference voltage source is connected to the negative output end of the DC-DC power conversion circuit, and the output end of the reference voltage source is connected to the base or gate of the second switch tube.

4. The on-grid and off-grid switching device according to claim 3, characterized in that: The reference voltage source includes a Zener diode and a fourth resistor and a fifth resistor connected in series, the fourth resistor and the fifth resistor are connected between the positive electrode of the reference voltage source and the negative electrode of the reference voltage source, the connection point of the fourth resistor and the fifth resistor is connected to the cathode of the Zener diode, the anode of the Zener diode is connected to the negative electrode of the reference voltage source, and the cathode of the Zener diode is also connected to the output end of the reference voltage source.

5. The on-grid and off-grid switching device according to any one of claims 1 to 4, characterized in that: The DC-DC power conversion circuit is a flyback DC-DC power conversion circuit.

6. The on-grid and off-grid switching device according to any one of claims 1 to 5, characterized in that: When the voltage across the second resistor and the third resistor is greater than the voltage threshold, the voltage at the connection point between the second resistor and the third resistor is greater than the reference voltage, the third switch tube is turned on, the second switch tube is turned off, and the first switch tube is turned off.

7. The on-grid and off-grid switching device according to any one of claims 1 to 6, characterized in that: When the voltage across the second resistor and the third resistor is less than or equal to the voltage threshold, the voltage at the connection point between the second resistor and the third resistor is less than or equal to the reference voltage, the third switch tube is turned off, the second switch tube is turned on, and the first switch tube is turned on.

8. A photovoltaic power generation system, characterized in that: The photovoltaic power generation system comprises a photovoltaic inverter and an on-grid and off-grid switching device, wherein the input end of the photovoltaic inverter is used to be connected to the output end of the photovoltaic array, the output end of the photovoltaic inverter is connected to the inverter port of the on-grid and off-grid switching device, the grid port of the on-grid and off-grid switching device is used to be connected to the grid, and the load port of the on-grid and off-grid switching device is used to be connected to the load; The on-grid and off-grid switching device comprises: A first switch and a second switch connected in series, wherein the first switch and the second switch are connected between the inverter port and the grid port, and a connection point between the first switch and the second switch is connected to the load port; A rectifier circuit, a capacitor and a DC-DC power conversion circuit, wherein the input end of the rectifier circuit is connected to the inverter port, the output end of the rectifier circuit is connected to the input end of the DC-DC power conversion circuit, the output end of the rectifier circuit includes a positive output end and a negative output end, and the capacitor is connected between the positive output end and the negative output end of the rectifier circuit; a first switch tube, a second switch tube, a third switch tube and a first resistor, the open-loop output end of the DC-DC power conversion circuit includes a positive output end and a negative output end, the emitter or source of the first switch tube is connected to the positive output end of the DC-DC power conversion circuit, the base or gate of the first switch tube is connected to the collector or drain of the second switch tube, the base or gate of the second switch tube is used to receive a reference voltage, the emitter or source of the second switch tube and the emitter or source of the third switch tube are connected to one end of the first resistor, the other end of the first resistor is connected to the negative output end of the DC-DC power conversion circuit, and the collector or drain of the third switch tube is connected to the collector or drain of the first switch tube; A second resistor and a third resistor connected in series, wherein the second resistor and the third resistor are connected between the collector or drain of the third switch tube and the negative output end of the DC-DC power conversion circuit, the connection point of the second resistor and the third resistor is connected to the base or gate of the third switch tube, and the collector or drain of the third switch tube and the negative output end of the DC-DC power conversion circuit are connected to the load in the on-grid and off-grid switching device; The first switch tube is a PNP transistor, a PMOS or a PIGBT; The second switch tube and the third switch tube are NPN transistors, NMOS or NIGBT.

9. The photovoltaic power generation system according to claim 8, characterized in that: The on-grid and off-grid switching device further includes a controller, and the DC-DC power conversion circuit further includes a closed-loop output terminal; The controller is used to obtain the voltage or current at the closed-loop output end and output a pulse width modulation signal. The voltage or current at the closed-loop output end is used to determine the duty cycle of the pulse width modulation signal. The pulse width modulation signal is used to control the switch tube in the DC-DC power conversion circuit.

10. The photovoltaic power generation system according to claim 9, characterized in that: The on-grid and off-grid switching device also includes a reference voltage source, the positive electrode of the reference voltage source is connected to the positive output end of the DC-DC power conversion circuit, the negative electrode of the reference voltage source is connected to the negative output end of the DC-DC power conversion circuit, and the output end of the reference voltage source is connected to the base or gate of the second switch tube.

11. The photovoltaic power generation system according to any one of claims 8 to 10, characterized in that: When the voltage across the second resistor and the third resistor is greater than the voltage threshold, the voltage at the connection point between the second resistor and the third resistor is greater than the reference voltage, the third switch tube is turned on, the second switch tube is turned off, and the first switch tube is turned off.

12. The photovoltaic power generation system according to any one of claims 8 to 11, characterized in that: When the voltage across the second resistor and the third resistor is less than or equal to the voltage threshold, the voltage at the connection point between the second resistor and the third resistor is less than or equal to the reference voltage, the third switch tube is turned off, the second switch tube is turned on, and the first switch tube is turned on.

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