A photovoltaic module reverse connection protection system

Abstract

The present invention discloses a reverse connection protection system for a photovoltaic module, comprising: a photovoltaic inverter, a PV unit is sequentially connected to a DC / DC circuit and a DC / AC circuit of the photovoltaic inverter, and the photovoltaic inverter further comprises a control device, the control device is adapted to output a DC / DC control signal PWM S1 and a DC / AC control signal PWM DC / AC , for controlling a switching tube S1 of the DC / DC circuit and the DC / AC circuit when the PV unit is correctly connected; a reverse connection protection device, when the PV unit is reversely connected, the reverse connection protection device is adapted to output a driving voltage V O , the driving voltage V O acts on the control device, so that the control device outputs a DC / DC control signal PWM S1 to turn on the switching tube S1, thereby protecting the body diode of the switching tube S1, which is beneficial to avoiding damage to the body diode of the body switching tube S1.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy power generation, and in particular to a reverse connection protection system for photovoltaic modules. Background Art

[0002] In a photovoltaic system, the correct connection of the cable between a photovoltaic inverter and a PV unit is crucial. If the PV unit is reversely connected, it may cause equipment failures, and even damage the PV unit and the photovoltaic inverter, bringing economic losses and safety hazards to users.

[0003] In related technologies, some photovoltaic inverters adopt anti-misconnection technologies for cable interfaces. By designing special interface structures, such as specific pin and jack layouts, etc., to prevent the positive and negative poles of the cable from being reversely connected. However, during the actual installation process, when the photovoltaic cable is pressed into the connector, the positive and negative cables may still be reversely connected, resulting in the failure of the anti-misconnection of the interface. Some photovoltaic inverters are connected in parallel with diodes having the same direction as the body diode at both ends of the DC-side switch tube to increase the current-carrying capacity and thus protect the switch tube. However, since the diode needs to withstand the short-circuit current and open-circuit voltage of the PV unit string, the selection requirements for the diode are extremely high, which in turn leads to a significant increase in cost. Summary of the Invention

[0004] An object of the present invention is to provide a reverse connection protection system for photovoltaic modules, which can effectively protect the body diode of the DC-side switch tube when the PV unit is reversely connected in the photovoltaic system.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a reverse connection protection system for photovoltaic modules, including: a photovoltaic inverter, the PV unit is sequentially connected to the DC / DC circuit and the DC / AC circuit of the photovoltaic inverter, and the photovoltaic inverter further includes a control device, and the control device is adapted to output a DC / DC control signal PWM S1 and a DC / AC control signal PWM DC / AC , for controlling the switch tube S1 of the DC / DC circuit and the DC / AC circuit when the PV unit is correctly connected; a reverse connection protection device, when the PV unit is reversely connected, the reverse connection protection device is adapted to output a driving voltage V O , the driving voltage V O acts on the control device, so that the control device outputs the DC / DC control signal PWM S1 to turn on the switch tube S1.

[0006] As a preference, the reverse connection protection device includes a power taking module and an energy storage module. The power taking module is used to take power from the DC side or the grid side of the photovoltaic system. The input side of the energy storage module is connected to the output side of the power taking module to store the energy output by the power taking module. The output side of the energy storage module is connected to the control device to supply power to the control device and enable the control device to output a DC / DC control signal PWM S1 to turn on the switching transistor S1.

[0007] As a preference, the reverse connection protection device further includes an anti-misoperation module. When the PV unit is reversely connected, the anti-misoperation module is adapted to turn on the power taking module and the energy storage module to output the driving voltage V to the control device O ; when the PV unit is correctly connected, the anti-misoperation module is adapted to disconnect the power taking module and the energy storage module.

[0008] As a preference, the anti-misoperation module includes a switch S2, a comparator, a voltage dividing resistor R1, a voltage dividing resistor R2, and a blocking diode D3; the switch S2 is connected between the power taking module and the energy storage module to connect or disconnect the power taking module and the energy storage module; the voltage dividing resistor R1, the voltage dividing resistor R2, and the blocking diode D3 are connected in series in sequence and are connected in parallel with the PV unit; one input end of the comparator is connected between the voltage dividing resistor R1 and the voltage dividing resistor R2, the other input end of the comparator is connected between the voltage dividing resistor R2 and the blocking diode D3, and the output end of the comparator acts on the switch S2 to make the switch S2 turn off when the PV unit is correctly connected and turn on when the PV unit is reversely connected.

[0009] As a preference, the reverse connection protection device further includes an auxiliary power source module. The auxiliary power source module is connected between the output side of the energy storage module and the control device and is used to convert the energy output by the energy storage module into the driving voltage V O , the driving voltage V O is adapted to supply power to the control device.

[0010] As a preference, the power taking module includes an inductor L2 and a blocking diode D2. The inductor L2 and the inductor L1 of the DC / DC circuit are wound on the same magnetic core. The inductor L2 is a secondary winding and the inductor L1 is a primary winding; the anode of the blocking diode D2 is connected to the inductor L2, and the cathode of the blocking diode D2 is connected to the energy storage module to keep the inductor L1 charging the energy storage module.

[0011] As a preference, the energy storage module includes a capacitor C1. The positive electrode of the capacitor C1 is connected to the cathode of the blocking diode D2, and the negative electrode of the capacitor is connected to the inductor L2.

[0012] As a preference, the control device includes a controller, a signal selection module and a DC / DC driving circuit. The controller is used for outputting a DC / AC control signal PWM DC / AC and a DC / DC intermediate signal PWM DC / DC . The DC / AC control signal PWM DC / AC acts on the DC / AC circuit. The DC / DC intermediate signal PWM DC / DC and the driving voltage V O act on the input end of the signal selection module. The output of the signal selection module acts on the input end of the DC / DC driving circuit. The DC / DC driving circuit is used for outputting a DC / DC control signal PWM S1 to control the switching tube S1 of the DC / DC circuit. The driving voltage V O is suitable for supplying power to the signal selection module and the DC / DC driving circuit.

[0013] As a preference, the signal selection module includes an OR gate unit, a voltage dividing resistor R a and a voltage dividing resistor R b . One input end of the OR gate unit is used for receiving the DC / DC intermediate signal PWM DC / DC ; the other input end of the OR gate unit is grounded through the voltage dividing resistor R b and is connected to the output side of the reverse connection protection device through the voltage dividing resistor R a to receive the driving voltage V O ; the output end of the OR gate unit acts on the DC / DC driving circuit.

[0014] As a preference, the photovoltaic module reverse connection protection system further includes a DC switch group. The DC switch group is connected between the PV unit and the DC / DC circuit; the DC switch group includes a bus switch S PV ; or the DC switch group includes a bus switch S PV , and a bus resistor R PV connected in parallel with the bus switch S PV ; when the PV unit is reversely connected, the controller is suitable for outputting a switch control signal S PV_ctl to disconnect the bus switch S PV .

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] In the case of reverse connection of the PV unit in the photovoltaic system, the control device can output a DC / DC control signal PWM through the reverse connection protection device S1Turn on the switching transistor S1, thereby protecting the body diode of the switching transistor S1, which is beneficial to avoid damage to the body diode of the body switching transistor S1. Description of the Drawings

[0017] Figure 1 Schematic diagram of the current in a photovoltaic system in the related art when the photovoltaic module is reversely connected.

[0018] Figure 2 Schematic diagram of a photovoltaic module reverse connection protection system according to some embodiments of the present application.

[0019] Figure 3 Architecture diagram of a photovoltaic module reverse connection protection system according to some embodiments of the present application.

[0020] Figure 4 Waveform diagram of the current of inductor L1, the current of inductor L2, and the voltage of capacitor C1 in a photovoltaic system according to some embodiments of the present application when the photovoltaic module is reversely connected.

[0021] Figure 5 Waveform diagram of the current of inductor L1 in a photovoltaic system according to some embodiments of the present application during normal operation.

[0022] Figure 6 Architecture diagram of a photovoltaic system according to some embodiments of the present application.

[0023] Figure 7 Architecture diagram of a photovoltaic system according to other embodiments of the present application.

[0024] In the figure: 101, PV unit; 102, photovoltaic inverter; 201, DC / DC circuit; 202, DC / AC circuit; 203, control device; 2031, controller; 2032, signal selection module; 2033, DC / DC drive circuit; 103, reverse connection protection device; 301, power extraction module; 302, anti-misoperation module; 303, energy storage module; 304, auxiliary power source module; 105, DC switch group. Detailed Embodiments

[0025] Next, in combination with the specific embodiments, the present invention will be further described. It should be noted that, on the premise of no conflict, the following described embodiments or technical features can be combined arbitrarily to form new embodiments.

[0026] The terms "including" and "having" and any variations thereof in the specification and claims of the present application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products, or devices.

[0027] In the description of the present invention, it should also be noted that unless otherwise clearly specified and defined, the terms "set", "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or connected by contact or indirectly through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] For the convenience of understanding the following solutions, the present application will be described through a photovoltaic system. As Figure 1 shown, it is a photovoltaic system in the related art. Among them, the PV unit is connected to the grid through the DC / DC circuit and the DC / AC circuit of the photovoltaic inverter. Specifically, the DC / DC circuit includes an inductor L1 and a switching tube S1. Among them, the inductor L1 and the switching tube S1 are connected in series and then connected in parallel with the PV unit. It should be understood that when the PV unit is connected correctly, the cathode of the body diode of the switching tube S1 is connected to the positive electrode of the PV unit, and the anode of the body diode of the switching tube S1 is connected to the negative electrode of the PV unit. Therefore, the body diode of the switching tube S1 is suitable for being in the cut-off state most of the time. When the PV unit is reversely connected, as Figure 1 shown, the anode of the body diode of the switching tube S1 is connected to the positive electrode of the PV unit, and the cathode of the body diode of the switching tube S1 is connected to the negative electrode of the PV unit. Therefore, the body diode of the switching tube S1 is in the conducting state, and the photovoltaic system forms a short-circuit loop of "positive electrode of the PV unit → body diode of the switching tube S1 → inductor L1 → negative electrode of the PV unit". If the short-circuit current is large and the current-carrying capacity of the body diode of the switching tube S1 is weak, it may cause damage to the body diode, and then lead to equipment failure, and even damage the PV unit and the photovoltaic inverter, bringing economic losses and safety hazards to users.

[0029] In the related art, some photovoltaic inverters adopt a cable interface anti-fooling technology. By designing a special interface structure, such as a specific pin and jack layout, etc., to prevent the positive and negative poles of the cable from being reversely connected. However, during the actual installation process, when the photovoltaic cable is pressed into the connector, the positive and negative cables may still be reversely connected, resulting in the failure of the interface anti-fooling. Some photovoltaic inverters connect a diode with the same direction as the body diode in parallel at both ends of the DC-side switching tube to increase the current-carrying capacity and thus protect the switching tube. However, since the diode needs to withstand the short-circuit current and open-circuit voltage of the PV unit string, the requirements for the selection of the diode are extremely high, which in turn leads to a significant increase in cost.

[0030] Based on the above content, in order to effectively protect the body diode of the switching tube S1 and reduce costs when the PV unit 101 is reversely connected in the photovoltaic system, the present application provides a photovoltaic module reverse connection protection system, asFigures 2 - 7 As shown in the figure, it includes: a photovoltaic inverter 102. The PV unit 101 is sequentially connected to the DC / DC circuit 201 and the DC / AC circuit 202 of the photovoltaic inverter 102. The photovoltaic inverter 102 further includes a control device 203 and an anti-reverse connection protection device 103. The control device 203 is adapted to output a DC / DC control signal PWM S1 and a DC / AC control signal PWM DC / AC , for when the PV unit 101 is correctly connected, to control the switching tube S1 of the DC / DC circuit 201 and the DC / AC circuit 202. When the PV unit 101 is reversely connected, the anti-reverse connection protection device 103 is adapted to output a driving voltage V O , the driving voltage V O acts on the control device 203, so that the control device 203 outputs a DC / DC control signal PWM S1 to turn on the switching tube S1.

[0031] That is to say, when the PV unit 101 is normally connected, the control device 203 normally outputs a DC / DC control signal PWM S1 to control the closing and opening of the switching tube S1, and normally outputs a DC / AC control signal PWM DC / AC to control the closing and opening of each switching tube in the DC / AC circuit 202. Further, when the PV unit 101 is reversely connected in the photovoltaic system, through the driving voltage V output by the anti-reverse connection protection device 103 O so that the control device 203 outputs a DC / DC control signal PWM S1 , and then turn on the switching tube S1, so that the short-circuit current flows through the switching tube S1, to play a role in protecting the body diode of the switching tube S1, which is beneficial to avoiding damage to the body diode of the body switching tube S1.

[0032] In some embodiments, as Figure 2 shown, the control device 203 includes a controller 2031, a signal selection module 2032 and a DC / DC drive circuit 2033. The controller 2031 is used to output a DC / AC control signal PWM DC / AC and a DC / DC intermediate signal PWM DC / DC , wherein, the DC / AC control signal PWM DC / AC acts on the DC / AC circuit 202 to control the closing and opening of each switching tube in the DC / AC circuit 202. The DC / DC intermediate signal PWM DC / DC and the driving voltage V O act on the input end of the signal selection module 2032. The output of the signal selection module 2032 acts on the input end of the DC / DC drive circuit 2033. The DC / DC drive circuit 2033 is used to output a DC / DC control signal PWM S1, to control the closing and opening of the switching transistor S1 of the DC / DC circuit 201.

[0033] That is to say, when the PV unit 101 is connected correctly, the signal selection module 2032 can output the driving signal level of the DC / DC driving circuit 2033 under the action of the DC / DC intermediate signal PWM DC / DC , so that the DC / DC driving circuit 2033 outputs the DC / DC control signal PWM S1 , to enable the normal operation of the photovoltaic system. Further, when the PV unit 101 is reversely connected, the reverse connection protection device 103 outputs the driving voltage V O , and the signal selection module 2032 can convert the driving voltage V O into the driving signal level of the DC / DC driving circuit 2033, so that the DC / DC driving circuit 2033 outputs the DC / DC control signal PWM S1 , to close the switching transistor S1, and the short-circuit current flows through the switching transistor S1 with a larger current-carrying capacity, which is beneficial to avoiding damage to the body diode of the switching transistor S1.

[0034] In addition, the driving voltage V O is suitable for supplying power to the signal selection module 2032 and the DC / DC driving circuit 2033. That is to say, when the PV unit 101 is reversely connected, the driving voltage V O not only serves as the input signal of the signal selection module 2032, but also supplies power to the signal selection module 2032 and the DC / DC driving circuit 2033, enabling the signal selection module 2032 and the DC / DC driving circuit 2033 to work normally, so that the DC / DC driving circuit 2033 can output the DC / DC control signal PWM S1 to turn on the switching transistor S1.

[0035] In some embodiments, as Figure 3 shown, the signal selection module 2032 includes an OR gate unit, a voltage-dividing resistor R a and a voltage-dividing resistor R b . One input terminal of the OR gate unit is used to receive the DC / DC intermediate signal PWM DC / DC ; the other input terminal of the OR gate unit is grounded through the voltage-dividing resistor R b and is connected to the output side of the reverse connection protection device 103 through the voltage-dividing resistor R a to receive the driving voltage V O ; the output terminal of the OR gate unit acts on the DC / DC driving circuit 2033.

[0036] It should be understood that through the voltage-dividing resistor R a and the voltage-dividing resistor R b , the driving voltage V OConverting to an appropriate drive signal level helps avoid damage to the DC / DC drive circuit 2033 caused by too high a drive signal level or ineffective driving of the DC / DC drive circuit 2033 due to too low a drive signal level. In addition, by adjusting the resistance values of the voltage-dividing resistors R a and the voltage-dividing resistor R b , the drive signal level output by the signal selection module 2032 can be conveniently and quickly debugged, improving the applicability of the signal selection module 2032.

[0037] It is worth noting that the circuit designs of the voltage-dividing resistors R a and the voltage-dividing resistor R b are simple and have low costs, facilitating later replacement and maintenance, thereby reducing the cost of the PV module reverse connection protection system. Moreover, the signal transmission delay of the circuits of the voltage-dividing resistors R a and the voltage-dividing resistor R b is small, improving the response speed of the signal selection module 2032. Thus, when the PV unit 101 is reversely connected, the switch tube S1 can be turned on faster, improving the reliability of the PV module reverse connection protection system and further reducing the risk of damage to the body diode of the switch tube S1 and even the PV system.

[0038] It should be known that the specific structure and working principle of the OR gate unit are well-known technologies to those skilled in the art, so they will not be elaborated in detail here; the working logic of the OR gate unit is to output a high level when at least one input terminal is at a high level and to output a low level when all input terminals are at a low level.

[0039] In some embodiments, as Figure 2 shown, the reverse connection protection device 103 includes a power extraction module 301 and an energy storage module 303. The power extraction module 301 is used to extract power from the DC side or the grid side of the PV system. The input side of the energy storage module 303 is connected to the output side of the power extraction module 301 to store the energy output by the power extraction module 301. The output side of the energy storage module 303 is connected to the control device 203 to supply power to the control device 203 and enable the control device 203 to output a DC / DC control signal PWM S1 to turn on the switch tube S1.

[0040] It should be understood that the power extraction module 301 can extract power from the DC side so that part of the energy after the PV unit 101 is reversely connected forms a drive voltage V O , which further acts on the control device 203 to output a DC / DC control signal PWM S1Turn on the switch tube S1. Through this design, the reverse connection protection device 103 is made independent of the grid side, reducing the dependence of the reverse connection protection device 103 on the grid and reducing the sensitivity of the reverse connection protection device 103 to fluctuations and interference on the grid side, thereby improving the stability and reliability of the PV module reverse connection protection system. The power acquisition module 301 can also obtain power from the grid side, which is beneficial to ensuring that the power acquisition module 301 obtains sufficient energy to be stored in the energy storage module 303, enabling the energy storage module 303 to have sufficient energy for the control device 203, and further improving the reliability of the PV module reverse connection protection system.

[0041] Further, the energy storage module 303 stores the energy output by the power acquisition module 301 and outputs energy to the signal selection module 2032 and the DC / DC drive circuit 2033 of the control device 203. Thus, through the collaborative work of the power acquisition module 301 and the energy storage module 303, the driving voltage V output by the reverse connection protection device 103 O is improved in stability and reliability.

[0042] In some embodiments, the power acquisition module 301 includes an inductor L2 and a blocking diode D2. The inductor L2 and the inductor L1 of the DC / DC circuit 201 are wound on the same magnetic core. Among them, the inductor L2 is the secondary winding and the inductor L1 is the primary winding. Thus, when a short-circuit current flows through the inductor L1, the inductor L2 generates an induced voltage and outputs the induced voltage to the energy storage module 303. Further, the anode of the blocking diode D2 is connected to the inductor L2, and the cathode of the blocking diode D2 is connected to the energy storage module 303 to keep the inductor L1 charging the energy storage module 303. That is to say, the blocking diode D2 helps to prevent the energy storage module 303 from discharging to the inductor L2, reducing the power loss of the energy storage module 303.

[0043] In some embodiments, as Figure 3 shown, the energy storage module 303 includes a capacitor C1. The positive electrode of the capacitor C1 is connected to the cathode of the blocking diode D2, and the negative electrode of the capacitor is connected to the inductor L2. That is to say, the blocking diode D2 keeps the inductor L2 charging the capacitor C1, which helps to prevent the capacitor C1 from discharging to the inductor L2, thereby reducing the energy loss of the capacitor C1. It should be understood that the capacitor C1 can complete charging in a short time, which is beneficial to improving the response speed of the reverse connection protection device 103. Further, after the situation of reverse connection of the PV unit 101 occurs, the reverse connection protection device 103 can output the driving voltage V in a short time Oto act on the control device 203. In addition, compared with a chemical battery, the capacitor C1 in this embodiment has a longer charge-discharge cycle life, which is beneficial to extending the service life of the reverse connection protection device 103 and reducing the maintenance cost. It is worth mentioning that the energy storage module 303 can also be implemented as a battery, a supercapacitor, etc., and the present application does not make specific limitations in this regard.

[0044] In at least one embodiment, as Figure 3 and Figure 4 shown, at time t0, the PV unit 101 is reversely connected to the photovoltaic inverter 102, forming a short-circuit loop as Figure 1 shown. Due to the action of the inductor L1 of the DC / DC circuit 201, in the Figure 4 shown time period from t0 to t2, the current i l1 flowing through the inductor L1 gradually increases, and reaches the peak value I1 at time t2, and remains constant after time t2. In the l1 shown time period from t0 to t1, the current i Figure 4 flowing through the inductor L2 gradually increases, and reaches the peak value I l2 at time t1; in the time period from t1 to t2, the current i l2 flowing through the inductor L2 gradually decreases, drops to 0 at time t2, and remains constant after time t2. l2max ; in the time period from t1 to t2, the current i l2 flowing through the inductor L2 gradually decreases, drops to 0 at time t2, and remains constant after time t2.

[0045] Furthermore, the induced voltage V l2 across the inductor L2 of the power extraction module 301 is positive on the left and negative on the right in Figure 3 , thus blocking the conduction of the diode D2, and the inductor L2 can charge the capacitor C1 of the energy storage module 303. In the Figure 4 shown time period from t0 to t2, the voltage V c1 across the capacitor C1 gradually increases, and reaches the peak value V c1 at time t2, and gradually decreases after time t2 due to output to the control device 203. Specifically, in the time period from t0 to t2, the energy generated by the inductor L2 is denoted as W max , W L2 , W L2 = 2×(1 / 2×L -2 ×I l2max 2 ), where L -2 is the inductance value of the inductor L2, and I l2max is the peak value reached by the current flowing through the inductor L2 at time t2. Furthermore, ignoring the energy loss in the blocking diode D2 and the circuit, the energy generated by the inductor L2 is equal to the energy stored in the capacitor C1. Therefore, the energy stored in the capacitor C1 is denoted as W C1 , WL2 =W C1 , that is, 2 × (1 / 2 × L -2 ×I l2max 2 ) = 1 / 2 × C -1 ×V c1 2 , where C -1 is the capacitance value of capacitor C1. By solving, we can get V c1 =(2 × L -2 ×i l2max 2 / C -1 ) 1 / 2 .

[0046] As can be seen from the above, the magnitude of the inductance value L -2 will affect the energy W L2 generated by inductor L2. Further, the magnitude of the inductance value L -2 and the magnitude of the capacitance value C -1 will jointly affect the voltage V c1 across capacitor C1. And, the energy W L2 generated by inductor L2 and the drive voltage V O will affect the time that the reverse connection protection device 103 can supply power to the signal selection module 2032 and the DC / DC drive circuit 2033 of the control device 203, that is, the conduction time of the switching transistor S1. Therefore, it is necessary to reasonably set the magnitude of the inductance value L -2 and the capacitance value C -1 according to the actual working conditions, and the present application does not make specific limitations on this.

[0047] Figure 2 In some embodiments, as shown in Figure 2 and Figure 3 , the reverse connection protection device 103 further includes an auxiliary power source module 304. The auxiliary power source module 304 is connected between the output side of the energy storage module 303 and the control device 203, and is used to convert the energy output by the energy storage module 303 into a drive voltage V O , and the drive voltage V O is suitable for supplying power to the control device 203. It should be understood that the voltage V c1 across capacitor C1 may be unstable, or the voltage range of the voltage V c1 is not adapted to the signal selection module 2032 and the DC / DC drive circuit 2033 of the control device 203. Through the auxiliary power source module 304, the voltage V c1 is converted into a drive voltage V O whose voltage range is adapted to the signal selection module 2032 and the DC / DC drive circuit 2033.

[0048] In addition, the auxiliary power source module 304 also reduces the ripple, improves the quality, and stably outputs the driving voltage V O , thereby providing a reliable power supply for the signal selection module 2032 and the DC / DC driving circuit 2033. It is worth mentioning that the voltage V c1 across the capacitor C1 will affect the design of the auxiliary power source module 304. Therefore, it is necessary to reasonably set the inductance value L -2 and the capacitance value C -1 according to the actual working conditions, so that the auxiliary power source module 304 is adapted to the voltage V c1 , the driving voltage V O . The auxiliary power source module 304 can be implemented as a voltage conversion circuit such as an LDO circuit, a Buck circuit, a Boost circuit, a Buck-Boost circuit, etc. This application does not make specific limitations on this.

[0049] In some embodiments, as Figure 2 shown, the reverse connection protection device 103 further includes an anti-misoperation module 302. When the PV unit 101 is reversely connected, the anti-misoperation module 302 is adapted to conduct the power taking module 301 and the energy storage module 303 to output the driving voltage V O to the control device 203; when the PV unit 101 is correctly connected, the anti-misoperation module 302 is adapted to disconnect the power taking module 301 and the energy storage module 303.

[0050] It should be understood that when the PV unit 101 is correctly connected, that is, when the DC / DC circuit 201 is working normally, the waveform of the current i l1 flowing through the inductor L1 of the DC / DC circuit 201 is as Figure 5 shown. During the time period from t0 to t1, the inductor current i l1 decreases from I l1max to I l1min . At this time, the induced voltage V l2 across the inductor L2 of the power taking module 301 is positive on the left and negative on the right in Figure 3 , and the capacitor C1 is charged. Specifically, V l2 = L -2 × (di l2 / dt). When V l2 is greater than the start-up voltage of the auxiliary power source module 304, or the voltage V c1 across the capacitor C1 is greater than the start-up voltage of the auxiliary power source module 304, the auxiliary power source module 304 will output the driving voltage V O , which will cause the switching transistor S1 to be mis-conducted and affect the normal operation of the photovoltaic inverter 102.

[0051] In this embodiment, through the anti-misoperation module 302, the power taking module 301 and the energy storage module 303 can be disconnected when the PV unit 101 is correctly connected, which is beneficial to avoiding the voltage V across the capacitor C1c1 greater than the starting voltage of the auxiliary power module 304, resulting in the output driving voltage V of the auxiliary power module 304 O ; it is also beneficial to avoid overcharging of the capacitor C1 caused by the inductor L2 continuously charging the capacitor C1, thereby improving the reliability and safety of the reverse connection protection device 103. In addition, through the anti-mis-touch module 302, when the PV unit 101 is correctly connected, the power-taking module 301 and the auxiliary power module 304 can be disconnected, which is beneficial to avoid the induced voltage V at both ends of the inductor L2 l2 greater than the starting voltage of the auxiliary power module 304, resulting in the output driving voltage V of the auxiliary power module 304 O , effectively preventing the mis-conduction of the switching transistor S1.

[0052] In some embodiments, as Figure 3 shown, the anti-mis-touch module 302 includes a switch S2, a comparator, a voltage-dividing resistor R1, a voltage-dividing resistor R2, and a blocking diode D3. Among them, the switch S2 is connected between the power-taking module 301 and the energy storage module 303 to connect or disconnect the power-taking module 301 and the energy storage module 303, and to connect or disconnect the power-taking module 301 and the auxiliary power module 304. Further, the voltage-dividing resistor R1, the voltage-dividing resistor R2, and the blocking diode D3 are connected in series in sequence and are connected in parallel with the PV unit 101; that is, after the voltage-dividing resistor R1, the voltage-dividing resistor R2, and the blocking diode D3 are connected in series, the whole is connected in parallel with the PV unit 101. Even further, one input terminal of the comparator is connected between the voltage-dividing resistor R1 and the voltage-dividing resistor R2, the other input terminal of the comparator is connected between the voltage-dividing resistor R2 and the blocking diode D3, and the output terminal of the comparator acts on the switch S2 to disconnect the switch S2 when the PV unit 101 is correctly connected and close the switch S2 when the PV unit 101 is reversely connected. That is, the comparator can compare the voltages between the two input terminals to determine whether the PV unit 101 is reversely connected, and output corresponding high-level signals or low-level signals to control the disconnection and closing of the switch S2.

[0053] It should be understood that the power-taking module 301, the anti-mis-touch module 302, the energy storage module 303 of the reverse connection protection device 103, and the signal selection module 2032 of the control device 203 all adopt hardware devices, which can improve the response speed of the reverse connection protection device 103 and the control device 203, thereby effectively protecting the body diode of the switching transistor S1. Moreover, compared with the scheme of connecting diodes in parallel in the related art, the cost of the photovoltaic module reverse connection protection system of the present application is lower.

[0054] In at least one embodiment, as Figure 3As shown, the positive input terminal of the comparator is connected between the voltage dividing resistor R2 and the blocking diode D3, and the negative input terminal of the comparator is connected between the voltage dividing resistor R1 and the voltage dividing resistor R2. Specifically, when the PV unit 101 is connected correctly, the cathode of the blocking diode D3 is connected to the positive electrode of the PV unit 101 through the voltage dividing resistor R2 and the voltage dividing resistor R1, and the anode of the blocking diode D3 is connected to the negative electrode of the PV unit 101, so that the blocking diode D3 is in the cut-off state, and thus the comparator outputs a low level, causing the switch S2 to open. When the PV unit 101 is connected reversely, the cathode of D3 is connected to the negative electrode of the PV unit 101 through the voltage dividing resistor R2 and the voltage dividing resistor R1, and the anode of the blocking diode D3 is connected to the positive electrode of the PV unit 101, so that the blocking diode D3 is in the conducting state, and thus the voltage of the positive input terminal of the comparator is higher than that of the negative input terminal, and the comparator outputs a high level, causing the switch S2 to conduct.

[0055] It should be understood that the switch S2 can also be a switch that conducts at a low level and disconnects at a high level, and by adjusting the connection direction of the blocking diode D3 and the connection positions of the positive and negative input terminals of the comparator, the above effect that the switch S2 disconnects when the PV unit 101 is connected correctly and closes when the PV unit 101 is connected reversely can be achieved. The present application does not make specific limitations on this.

[0056] In at least one embodiment, the switch S2 is a normally closed switch to improve the reliability of the reverse connection protection device 103, so that the switch S2 closes in the event of an unexpected situation, and the reverse connection protection device 103 outputs the driving voltage V O acting on the control device 203, causing the switching transistor S1 to close, and further playing a role in protecting the body diode of the switching transistor S1. It is worth mentioning that the switch S2 can also be a normally open switch. The present application does not make specific limitations on this.

[0057] In some embodiments, as Figure 6 and Figure 7 shown, the photovoltaic module reverse connection protection system further includes a DC switch group 105, and the DC switch group 105 is connected between the PV unit 101 and the DC / DC circuit 201; the DC switch group 105 includes a bus switch S PV ; or the DC switch group 105 includes a bus switch S PV , and a bus resistor R PV connected in parallel with the bus switch S PV ; when the PV unit 101 is connected reversely, the controller 2031 is adapted to output a switch control signal S PV_ctl , so that the bus switch S PV disconnects, so that the PV unit 101 disconnects from the photovoltaic inverter 102, cutting off the short-circuit loop, so as to play a role in protecting the PV unit 101 and the photovoltaic inverter 102.

[0058] It should be understood that when the PV unit 101 is reversely connected, the controller 2031 outputs the switch control signal S PV_ctl , so that the bus switch S PV is disconnected, thus cutting off the short - circuit loop; meanwhile, the reverse - connection protection device 103 outputs the driving voltage V O , and outputs the DC / DC control signal PWM S1 through the signal selection module 2032 and the DC / DC driving circuit 2033 to turn on the switching transistor S1, so that the short - circuit current flows through the switching transistor S1 with a larger current - carrying capacity. That is to say, the disconnection of the bus switch S PV and the turning on of the switching transistor S1 are two synchronous and independent actions. Therefore, in the case where one of them fails, the other can still function properly, which is beneficial to improving the safety of the photovoltaic system.

[0059] In at least one embodiment, as Figure 6 shown, the DC switch group 105 includes the bus switch S PV . Specifically, a positive - bus switch S PV+ and a negative - bus switch S PV- are respectively arranged on the positive bus and the negative bus between the PV unit 101 and the DC / DC circuit 201. When the PV unit 101 is reversely connected, the controller 2031 is adapted to output the switch control signal S PV_ctl to disconnect the positive - bus switch S PV+ and the negative - bus switch S PV- , thereby cutting off the short - circuit loop generated during PV reverse connection to improve the safety of the photovoltaic system.

[0060] In at least one embodiment, as Figure 7 shown, the DC switch group 105 includes the bus switch S PV , and a bus resistance R PV connected in parallel with the bus switch S PV . Specifically, a positive - bus switch S PV+ and a negative - bus switch S PV- are respectively arranged on the positive bus and the negative bus between the PV unit 101 and the DC / DC circuit 201. Each positive - bus switch S PV + and negative - bus switch S PV- are respectively connected in parallel with the resistance bus resistance R PV . It should be understood that when starting up, each bus switch S PV of the DC switch is disconnected. When the controller 2031 recognizes that the PV unit 101 is correctly connected, the positive - bus switch S PV+ and the negative - bus switch S PV- are closed, and the bus resistance R PVWhen it is short-circuited, the photovoltaic system can work normally; when the controller 2031 recognizes that the PV unit 101 is correctly connected, the controller 2031 is adapted to output a switching control signal S PV_ctl , such that the positive bus switch S PV+ and the negative bus switch S PV- are disconnected, and the short-circuit current flows through the bus resistance R PV , thereby reducing the short-circuit current through the bus resistance R PV , so as to further reduce the damage to the switching transistor S1 and the body diode of the switching transistor S1 caused by the short-circuit current, and improve the safety of the photovoltaic system. It is worth mentioning that due to the existence of the bus resistance R PV , it is difficult to completely cut off the short-circuit loop. Therefore, an RSD device needs to be used to disconnect the PV unit 101 from the photovoltaic inverter 102 when the PV unit 101 is reversely connected.

[0061] In at least one embodiment, the bus resistance R PV is implemented as a PTC resistor. Furthermore, the resistance value can be rapidly increased through the self-heating of the PTC resistor, thereby limiting the current, protecting the switching transistor S1 and the circuit of the photovoltaic system from damage, and also saving costs.

[0062] The above describes the basic principle, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

Claims

1. A photovoltaic module reverse connection protection system, characterized in that: include: Photovoltaic inverter, PV unit is connected with DC / DC circuit and DC / AC circuit of the photovoltaic inverter in sequence, the photovoltaic inverter also includes a control device, the control device is suitable for outputting DC / DC control signal PWM S1 and DC / AC control signal PWM DC / AC , used to control the switch tube S1 of the DC / DC circuit and the DC / AC circuit when the PV unit is positively connected; A reverse connection protection device, when the PV unit is reversely connected, the reverse connection protection device is suitable for outputting a driving voltage V O , the driving voltage V O Acting on the control device so that the control device outputs the DC / DC control signal PWM S1 Turn on the switch tube S1; The reverse connection protection device includes a power supply module and an energy storage module. The power supply module is used to obtain power from the DC side or the grid side of the photovoltaic system. The input side of the energy storage module is connected to the output side of the power supply module to store the energy output by the power supply module. The output side of the energy storage module is connected to the control device to supply power to the control device and enable the control device to output a DC / DC control signal PWM. S1 To turn on the switch tube S1; The reverse connection protection device further comprises an anti-mistaken touch module. When the PV unit is reversely connected, the anti-mistaken touch module is adapted to conduct the power taking module and the energy storage module to output the driving voltage V to the control device. O When the PV unit is connected, the anti-mistaken touch module is suitable for disconnecting the power extraction module and the energy storage module; The anti-mistouch module includes a switch S2, a comparator, a voltage-dividing resistor R1, a voltage-dividing resistor R2 and a blocking diode D3; the switch S2 is connected between the power taking module and the energy storage module to connect or disconnect the power taking module and the energy storage module; the voltage-dividing resistor R1, the voltage-dividing resistor R2 and the blocking diode D3 are connected in series in sequence and in parallel with the PV unit; one of the input ends of the comparator is connected between the voltage-dividing resistor R1 and the voltage-dividing resistor R2, and the other input end of the comparator is connected between the voltage-dividing resistor R2 and the blocking diode D3, and the output end of the comparator acts on the switch S2 to make the switch S2 disconnected when the PV unit is forwardly connected and closed when the PV unit is reversely connected.

2. The photovoltaic module reverse connection protection system according to claim 1, characterized in that: The reverse connection protection device also includes an auxiliary source module, which is connected between the output side of the energy storage module and the control device, and is used to convert the energy output by the energy storage module into the driving voltage V O , the driving voltage V O Suitable for supplying power to the control device.

3. The photovoltaic module reverse connection protection system according to any one of claims 1-2, characterized in that: The power taking module includes an inductor L2 and a blocking diode D2. The inductor L2 and the inductor L1 of the DC / DC circuit are wound on the same magnetic core. The inductor L2 is a secondary winding, and the inductor L1 is a primary winding. The anode of the blocking diode D2 is connected to the inductor L2, and the cathode of the blocking diode D2 is connected to the energy storage module to keep the inductor L1 charging the energy storage module.

4. The photovoltaic module reverse connection protection system according to claim 3, characterized in that: The energy storage module includes a capacitor C1 , a positive electrode of the capacitor C1 is connected to a cathode of the blocking diode D2 , and a negative electrode of the capacitor is connected to the inductor L2 .

5. The photovoltaic module reverse connection protection system according to any one of claims 1-2, characterized in that: The control device includes a controller, a signal selection module and a DC / DC drive circuit. The controller is used to output a DC / AC control signal PWM. DC / AC and DC / DC intermediate signal PWM DC / DC , the DC / AC control signal PWM DC / AC Acting on the DC / AC circuit, the DC / DC intermediate signal PWM DC / DC and the driving voltage V O The output of the signal selection module acts on the input end of the DC / DC drive circuit, and the DC / DC drive circuit is used to output a DC / DC control signal PWM. S1 , to control the switch tube S1 of the DC / DC circuit; the driving voltage V O Suitable for supplying power to the signal selection module and the DC / DC driving circuit.

6. The photovoltaic module reverse connection protection system according to claim 5, characterized in that: The signal selection module includes an OR gate unit, a voltage dividing resistor R a And the voltage divider resistor R b One of the input terminals of the OR gate unit is used to receive the DC / DC intermediate signal PWM DC / DC The other input terminal of the OR gate unit is connected through a voltage divider resistor R b grounded and connected to the voltage divider resistor R a Connected to the output side of the reverse connection protection device to receive the driving voltage V O ; The output end of the OR gate unit acts on the DC / DC drive circuit.

7. The photovoltaic module reverse connection protection system according to claim 6, characterized in that: It also includes a DC switch group, which is connected between the PV unit and the DC / DC circuit; the DC switch group includes a bus switch S PV ; or the DC switch group includes a bus switch S PV , and the bus switch S PV Parallel bus resistance R PV When the PV unit is reversed, the controller is adapted to output a switch control signal S PV_ctl , so that the bus switch S PV disconnect.

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