Voltage conversion unit, inverter, and photovoltaic power generation system

Abstract

The application provides a voltage conversion unit, an inverter and a photovoltaic power generation system. The voltage conversion unit provided by the application comprises a transformer, a primary circuit and a secondary circuit. The primary circuit comprises a switch tube, and the secondary circuit comprises a first circuit loop and a second circuit loop. The first circuit loop comprises a secondary winding of the transformer, a first switch unit and a first energy storage unit, and the second circuit loop comprises the secondary winding of the transformer, the first energy storage unit, a second switch unit and a second energy storage unit. The voltage conversion unit provided by the application can realize that the first switch unit is turned on and the second switch unit is not turned on when the switch tube is turned on, and realize that the second switch unit is turned on and the first switch unit is not turned on when the switch tube is turned off.

Description

Technical Field

[0001] This application relates to the field of photovoltaic power generation technology, and in particular to a voltage conversion unit, an inverter, and a photovoltaic power generation system. Background Technology

[0002] like Figure 1 As shown, the photovoltaic power generation system includes a photovoltaic module 101 and an inverter circuit 102. The positive (PV+) and negative (PV-) terminals of the photovoltaic module 101 are connected to the electrical signal input ports of the inverter circuit 102, and the electrical signal output ports of the inverter circuit 102 (including the neutral wire port L and the live wire port N) are used to connect to the AC power grid.

[0003] When illuminated, the photovoltaic module 101 generates a DC voltage signal and outputs it to the inverter circuit 102. The inverter circuit 102 then converts the DC voltage signal into an AC voltage signal and inputs it into the AC power grid. The state in which the photovoltaic module 101 generates a DC voltage signal under illumination can be referred to as the operating state.

[0004] Typically, when the photovoltaic module 101 is in operation, a negative voltage is generated between the negative electrode (PV-) of the photovoltaic module 101 and the grounded metal frame of the photovoltaic module 101. This negative voltage between the negative electrode (PV-) of the photovoltaic module 101 and the grounded metal frame causes a decrease in the output power of the entire photovoltaic power generation system. This phenomenon is commonly referred to as the potential-induced degradation (PID) effect.

[0005] Therefore, how to repair the PID effect in order to slow down the decline in the output power of the entire photovoltaic power generation system has become an urgent technical problem to be solved. Summary of the Invention

[0006] This application provides a voltage conversion unit, an inverter, and a photovoltaic power generation system, which can be used to mitigate the decline in the output power of the entire photovoltaic power generation system. Furthermore, it can reduce the number of turns in the secondary winding of the transformer in the inverter, thereby reducing the problems of large transformer size, high cost, and poor EMI characteristics of the transformer.

[0007] In a first aspect, this application provides a device for repairing the potential-induced degradation effect of a photovoltaic module. The device includes a transformer, a primary circuit, and a secondary circuit. The primary circuit includes a switching transistor. The secondary circuit includes a first circuit loop, which includes the secondary winding of the transformer, a first switching unit, and a first energy storage unit. The secondary circuit also includes a second circuit loop, which includes the secondary winding of the transformer, the first energy storage unit, a second switching unit, and a second energy storage unit. The positive terminal of the second energy storage unit is used to connect to the negative terminal of the photovoltaic module in the photovoltaic power generation system, and the negative terminal of the second energy storage unit is used to connect to ground. When the switching transistor is turned on, the first switching unit is turned on and the second switching unit is not turned on. When the switching transistor is turned off, the second switching unit is turned on and the first switching unit is not turned on.

[0008] In this embodiment, since the first switching unit is on and the second switching unit is off when the switching transistor in the primary circuit of the repair device is on, the first energy storage unit can be charged when the switching transistor in the primary circuit of the repair device is on. Conversely, since the second switching unit is on and the first switching unit is off when the switching transistor in the primary circuit of the repair device is off, the second energy storage unit can be charged when the switching transistor in the primary circuit of the repair device is off.

[0009] Since the positive terminal of the second energy storage unit in this embodiment is used to connect to the negative terminal of the photovoltaic module in the photovoltaic power generation system, and the negative terminal of the second energy storage unit is used to connect to ground, the repair voltage of the repair device when repairing the potential-induced degradation effect of the photovoltaic module is numerically equal to the voltage on the first energy storage unit when the switch in the primary circuit is turned on plus the voltage on the secondary winding when the switch in the primary circuit is turned off. In this case, if the voltage of the second energy storage unit to be output is fixed, since a portion of the voltage can be provided by the first energy storage unit, compared to the prior art where the voltage of the second energy storage unit is entirely provided by the voltage on the secondary winding, the voltage on the secondary winding when the switch in the primary circuit is turned off can be reduced. Furthermore, since the voltage on the secondary winding is usually related to the number of turns of the secondary winding, generally, the more voltage is required on the secondary winding, the more turns the corresponding secondary winding will have. Therefore, in this embodiment, since the voltage on the secondary winding when the switching transistor in the primary circuit is turned off can be reduced, the number of turns in the secondary winding can be reduced, thereby alleviating problems such as large transformer size and high cost. Furthermore, by reducing the number of turns in the secondary winding, the problem of poor EMI characteristics of the transformer is also reduced.

[0010] In conjunction with the first aspect, in one possible implementation, the first energy storage unit includes at least one first capacitor.

[0011] In conjunction with the first aspect, in one possible implementation, the second energy storage unit includes at least one second capacitor.

[0012] In conjunction with the first aspect, in one possible implementation, the first switching unit is a first diode, and the second switching unit is a second diode.

[0013] In conjunction with the first aspect, in one possible implementation, the negative terminal of the first diode is connected to the positive terminal of the second diode.

[0014] In conjunction with the first aspect, in one possible implementation, the first circuit loop further includes at least one current-limiting element connected in series with the first diode and the first energy storage unit.

[0015] In conjunction with the first aspect, in one possible implementation, the current-limiting element includes any one of the following: a resistor, an inductor, or a thermistor.

[0016] In a second aspect, this application provides an inverter including the repair device as described in the first aspect or any one of the aspects.

[0017] Thirdly, this application provides a photovoltaic power generation system, including the inverter as described in the second aspect.

[0018] Fourthly, this application provides a voltage conversion unit, which includes a transformer, a primary circuit, and a secondary circuit. The primary circuit includes a switching transistor. The secondary circuit includes a first circuit loop, which includes a secondary winding of the transformer, a first switching unit, and a first energy storage unit. The secondary circuit also includes a second circuit loop, which includes a secondary winding of the transformer, the first energy storage unit, a second switching unit, and a second energy storage unit. The secondary circuit also includes a first output port and a second output port, with the first output port connected to a first port of the second energy storage unit and the second output port connected to a second port of the second energy storage unit. When the switching transistor is turned on, the first switching unit is turned on and the second switching unit is not turned on; when the switching transistor is turned off, the second switching unit is turned on and the first switching unit is not turned on.

[0019] In this embodiment, since the first switching unit is on and the second switching unit is off when the switching transistor in the primary circuit is on, the first energy storage unit can be charged when the switching transistor in the primary circuit is on. Conversely, since the second switching unit is on and the first switching unit is off when the switching transistor in the primary circuit is off, the second energy storage unit can be charged when the switching transistor in the primary circuit is off.

[0020] It is understandable that if the voltage required for the second energy storage unit is fixed, since a portion of the voltage can be provided by the first energy storage unit, compared to the prior art where the voltage of the second energy storage unit relies entirely on the voltage of the secondary winding, the voltage on the secondary winding when the primary-side switch is turned off can be reduced. Furthermore, since the voltage on the secondary winding is usually related to the number of turns in the secondary winding, generally, the more voltage required on the secondary winding, the more turns are needed. Therefore, in this embodiment, the number of turns in the secondary winding can be reduced, thereby reducing the problems of large transformer size and high cost. Furthermore, it also reduces the problem of poor EMI characteristics in the transformer.

[0021] In conjunction with the fourth aspect, in one possible implementation, the first energy storage unit includes at least one first capacitor.

[0022] In this implementation, when the first switching unit is turned on, electrical energy can be stored through at least one capacitor.

[0023] In conjunction with the fourth aspect, in one possible implementation, the second energy storage unit includes at least one second capacitor.

[0024] In this implementation, when the second switching unit is turned on, electrical energy can be stored through at least one capacitor.

[0025] In conjunction with the fourth aspect, in one possible implementation, the first switching unit is a first diode, and the second switching unit is a second diode.

[0026] In conjunction with the fourth aspect, in one possible implementation, the negative terminal of the first diode is connected to the positive terminal of the second diode.

[0027] In conjunction with the fourth aspect, in one possible implementation, the first circuit loop further includes at least one current-limiting element connected in series with the first diode and the first energy storage unit. Exemplarily, the current-limiting element includes any of the following: a resistor, an inductor, or a thermistor.

[0028] In this implementation, the current in the first circuit loop can be limited by a current-limiting element.

[0029] Fifthly, this application provides an inverter including a voltage conversion unit as described in the first aspect or any of the aspects.

[0030] In conjunction with the fifth aspect, in one possible implementation, the inverter is also used to repair the potential-induced degradation (PID) generated by the photovoltaic module.

[0031] In conjunction with the fifth aspect, in one possible implementation, the first output port is used to connect to the negative terminal of the photovoltaic module, and the second output port is used to connect to ground.

[0032] In this implementation, since the first output port can be connected to the negative terminal of the photovoltaic module, the voltage of the negative terminal of the photovoltaic module to ground can be raised to the voltage of the first output port, thereby achieving the repair of the PID effect generated by the photovoltaic module.

[0033] Sixthly, this application provides a photovoltaic power generation system including an inverter as described in the fifth aspect or any one of them. Attached Figure Description

[0034] Figure 1 This is a structural schematic diagram of a photovoltaic power generation system provided in one embodiment of this application;

[0035] Figure 2 A schematic diagram of a circuit structure for repairing PID in the prior art provided in this application;

[0036] Figure 3 A schematic diagram of the circuit structure of a voltage conversion unit provided in one embodiment of this application;

[0037] Figure 4 A schematic diagram of the circuit structure of a voltage conversion unit provided in another embodiment of this application;

[0038] Figure 5 This is a structural schematic diagram of a voltage conversion unit provided in yet another embodiment of this application. Detailed Implementation

[0039] Photovoltaic power generation technology is a low-carbon, environmentally friendly, and green energy technology that is currently being used more and more widely. Typically, photovoltaic power generation technology can be achieved through photovoltaic power generation systems.

[0040] Figure 1 This is a structural schematic diagram of a photovoltaic power generation system provided in one embodiment of this application. Figure 1 As shown, the photovoltaic power generation system includes a photovoltaic module 101 and an inverter circuit 102. The positive (PV+) and negative (PV-) terminals of the photovoltaic module 101 are connected to the electrical signal input ports of the inverter circuit 102, and the electrical signal output ports of the inverter circuit 102 (including the neutral wire port L and the live wire port N) are used to connect to the AC power grid.

[0041] It should be noted here that... Figure 1 This embodiment only provides an example of a photovoltaic module 101. In real-world scenarios, the inverter circuit 102 can connect multiple photovoltaic modules 101 simultaneously. This application does not limit the scope of the embodiment.

[0042] It should also be noted that this application does not limit the specific form of the inverter circuit. For example, the inverter circuit can be a centralized inverter or a string inverter. A centralized inverter includes a combiner module, an inverter, and a transformer, while a string inverter includes an inverter and a transformer. The main function of the combiner module is to combine the output currents of multiple photovoltaic modules before sending them into the inverter. Of course, the above two inverter structures are merely examples; the inverter circuit in the embodiments of this application can also be implemented using inverters with other structures, and this application does not limit this. In addition, the photovoltaic power generation system may include other circuit structures besides photovoltaic modules and inverter circuits, such as maximum power point tracking (MPPT) circuits.

[0043] for Figure 1 In the photovoltaic power generation system shown, sunlight shines on the photovoltaic module 101, which converts the sunlight into a DC voltage signal and outputs it to the inverter circuit 102 via the positive (PV+) and negative (PV-) terminals. The inverter circuit 102 then converts the DC voltage signal into an AC voltage signal and inputs it into the AC power grid. The state in which the photovoltaic module 101 generates a DC voltage signal under sunlight can be referred to as the operating state.

[0044] Typically, when the photovoltaic module 101 is in operation, a negative voltage is generated between the negative electrode (PV-) of the photovoltaic module 101 and the grounded metal frame of the photovoltaic module 101. This negative voltage between the negative electrode (PV-) of the photovoltaic module and the grounded metal frame causes a decrease in the output power of the entire photovoltaic power generation system. Specifically, when the photovoltaic module 101 is operating during the day, a negative voltage exists between the negative electrode (PV-) of the photovoltaic module and the ground, resulting in a potential difference of several hundred volts or even several thousand volts between the negative electrode (PV-) of the photovoltaic module and the metal frame. Under the influence of this potential difference, alkali metal ions (such as sodium ions) in the encapsulation glass (tempered glass) migrate into the cell string of the photovoltaic module. When the alkali metal ions enter the cell string (for example, into the negative electrode of the cell string), it causes a continuous degradation in the power generation performance of the photovoltaic module, resulting in a significant decrease in the output power of the photovoltaic module.

[0045] As an example, when a photovoltaic (PV) module is operating, the voltage at its negative terminal (PV-) is -300 volts (V). At this voltage, there is a -300V voltage between the negative terminal (PV-) and the grounded metal frame. This -300V voltage causes a continuous degradation in the PV module's power generation performance, leading to a significant decrease in its output power. This phenomenon is commonly referred to as potential-induced degradation (PID) effect.

[0046] Therefore, how to repair the PID effect in order to slow down the decline in the output power of the entire photovoltaic power generation system has become an urgent technical problem to be solved.

[0047] Currently, a method for repairing PID has been provided in related technologies. Figure 2 This is a schematic diagram of a circuit used in the prior art to repair a PID controller. For example... Figure 2 As shown, by adding a voltage conversion unit to the inverter of the photovoltaic power generation system to generate a DC voltage source, and then applying the DC voltage source between the negative terminal (PV-) of the photovoltaic module and ground, and the direction of the generated DC voltage source is opposite to the direction of the DC voltage between the negative terminal PV- and ground when the photovoltaic module is working during the day, the PID is repaired.

[0048] like Figure 2 As shown, the voltage conversion unit consists of two parts: a primary circuit and a secondary branch. The input to the primary circuit is the phase voltage or line voltage of the mains power supply. The primary circuit provides energy to the secondary branch via a control switch. The secondary branch includes a winding L1, a diode D1, and a capacitor C1. Winding L1 provides the DC voltage source required by the secondary branch. Diode D1 and capacitor C1 are connected in series. One end of capacitor C1 is grounded, and the other end of capacitor C1 is connected to the negative terminal (PV-) of the photovoltaic module via switch K1. In practical implementation, during the period when the primary circuit is turned on by the control switch, the primary circuit stores energy in the iron core. Then, when the primary circuit is turned off by the control switch, the energy stored in the iron core is released, providing a DC voltage source for the secondary branch. Diode D1 turns on, and the current in the secondary branch flows through diode D1 and capacitor C1. At this time, the end of capacitor C1 connected to diode D1 is the positive terminal of capacitor C1 (the corresponding voltage is a positive voltage). Under these circumstances, when switch K1 is closed, the voltage value of the negative terminal (PV-) of the photovoltaic module to ground will be equal to the voltage value of capacitor C1. Furthermore, there will be a positive voltage between the negative terminal (PV-) and the grounded metal frame, thereby raising the voltage of the negative electrode (PV-) of the photovoltaic module to ground to a positive voltage.

[0049] Furthermore, it is understandable that in order to achieve the repair effect, the voltage value on capacitor C1 needs to be higher than or equal to the absolute value of the negative voltage between the negative terminal (PV-) of the photovoltaic module and the grounded metal frame when it is working during the day.

[0050] However, because the negative voltage between the negative electrode (PV-) of the photovoltaic module and the grounded metal frame is relatively high during daytime operation, the required voltage value on capacitor C1 will be relatively high (also known as high PID resistance), for example, greater than 300V. This results in a larger number of turns on winding L1, leading to problems such as a larger transformer size and higher cost. At the same time, the large number of turns on winding L1 also results in poor electromagnetic interference (EMI) characteristics of the transformer.

[0051] Therefore, embodiments of this application provide a voltage conversion unit, an inverter, and a photovoltaic power generation system that can achieve PID correction while reducing the number of turns on winding L1, thereby reducing problems such as large transformer size and high cost. Furthermore, it reduces the problem of poor EMI characteristics in the transformer.

[0052] It should be noted that, in the embodiments of this application, when repairing the PID effect generated by photovoltaic modules, the photovoltaic modules to be repaired can be one or more.

[0053] Figure 3 This is a schematic diagram of the circuit structure of a voltage conversion unit provided in one embodiment of this application. It should be noted that the circuit of the voltage conversion unit in this embodiment can be included in the inverter. Furthermore, the inverter may include other circuit structures, such as an inverter circuit, etc., which are not limited in this embodiment.

[0054] like Figure 3 As shown, the voltage conversion unit includes a secondary circuit 301, a primary circuit 302, and a transformer. The transformer includes a winding 3011 in the secondary circuit 301, a winding 3021 in the primary circuit 302, and an iron core. It should be noted that in this embodiment, winding 3011 is also referred to as the secondary winding 3011.

[0055] Specifically, the primary circuit includes a switching transistor 3022. The secondary circuit 301 includes a first circuit loop, which contains a secondary winding 3011, a first switching unit 3012, and a first energy storage unit 3013.

[0056] The secondary circuit 301 also includes a second circuit loop, which includes a secondary winding 3011, a first energy storage unit 3013, a second switching unit 3014, and a second energy storage unit 3015. The secondary circuit 301 also includes a first output port 3017 and a second output port 3019. The first output port 3017 is connected to the first port 3016 of the second energy storage unit, and the second output port 3019 is connected to the second port 3018 of the second energy storage unit. When the switching transistor 3022 is turned on, the first switching unit 3012 is turned on and the second switching unit 3014 is not turned on. When the switching transistor 3022 is turned off, the second switching unit 3014 is turned on and the first switching unit 3012 is not turned on.

[0057] In this embodiment, the secondary winding 3011 is a winding in the secondary circuit. Normally, the secondary winding 3011 and the winding 3021 in the primary circuit 302 are located on the same iron core. Specifically, the primary circuit 302 can control the primary switching transistor to apply a voltage to the winding 3021, thereby generating an alternating magnetic flux in the iron core. Furthermore, under the action of the magnetic flux, an electromotive force is induced in the secondary winding 3011, enabling the secondary circuit to operate.

[0058] It should be noted that the specific circuit structure of the primary-side circuit 302 is not limited in the embodiments of this application. For example, the primary-side circuit 302 may typically include a circuit structure that connects to the mains power to obtain alternating current, and a circuit structure that obtains rectified voltage through a rectifier.

[0059] It should be noted that this embodiment does not limit the specific material of the secondary winding 3011. For example, it can be wound with double-insulated flat wire or enameled wire. The concept of winding can also be found in the description in related technologies, and will not be repeated here.

[0060] In this embodiment, the secondary circuit can be considered to consist of two parts: a first circuit loop consisting of a secondary winding 3011, a first switching unit 3012 and a first energy storage unit 3013, and a second circuit loop consisting of a secondary winding 3011, a first energy storage unit 3013, a second switching unit 3014 and a second energy storage unit 3015.

[0061] It should be noted that in transformers, it is usually necessary to mark the same terminals on the primary winding in the primary circuit and the winding (also known as the secondary winding) in the secondary circuit so that the direction of the induced electromotive force in the secondary winding in the secondary circuit can be identified.

[0062] As an example, such as Figure 3As shown, the black dot in the primary circuit 302 (located at one end of winding 3021) and the black dot in the secondary circuit (located at one end of secondary winding 3011) represent terminals with the same name. If the black dot in the primary circuit represents the negative terminal, then the black dot in the secondary winding 3011 also represents the negative terminal. Correspondingly, the other end of winding 3021, corresponding to the end with the black dot, represents the positive terminal. In this case, without considering whether the circuit loop is conductive, the current direction for the first circuit loop should be from the positive terminal of secondary winding 3011, through the first switching unit 3012 and the first energy storage unit 3013, and then back to the negative terminal of secondary winding 3011. For the second circuit loop, the current direction should be from the positive terminal of secondary winding 3011, first through the second energy storage unit 3015, then through the second switching unit 3014 and the first energy storage unit 3013, and then back to the negative terminal of secondary winding 3011.

[0063] As another example, still using Figure 3 For example, if the black dot on the primary circuit represents the positive terminal, then the black dot on the secondary winding 3011 also represents the positive terminal. Correspondingly, the other end of the secondary winding 3011 corresponding to the black dot represents the negative terminal. In this case, without considering whether the circuit loop is conductive, the current direction for the first circuit loop should be from the positive terminal of the secondary winding 3011, passing through the first energy storage unit 3013, then the first switching unit 3012, and finally returning to the negative terminal of the secondary winding 3011. For the second circuit loop, the current direction should be from the positive terminal of the secondary winding 3011, passing through the first energy storage unit 3013, then the second switching unit 3014 and the second energy storage unit 3015, and finally returning to the negative terminal of the secondary winding 3011.

[0064] For detailed information on the same-name endpoint, please refer to the descriptions in relevant technologies; they will not be repeated here.

[0065] In this embodiment, the first energy storage unit 3013 or the second energy storage unit 3015 refers to a component used to store electrical energy, such as a capacitor.

[0066] In this embodiment, the first switching unit 3012 refers to a switch that can control the first circuit loop to be turned on or off. For example, the first switching unit 3012 is a diode, or other components that have the same function as a diode. This application embodiment does not limit this.

[0067] In this embodiment, the second switching unit 3014 refers to a switch that can control the second circuit loop to be turned on or off. For example, the second switching unit 3014 is a diode, or other components that have the same function as a diode. This application embodiment does not limit this.

[0068] In this embodiment, when the switching transistor 3022 in the primary circuit is turned on, the first switching unit 3012 is turned on and the second switching unit 3014 is not turned on. When the switching transistor 3022 in the primary circuit is turned off, the second switching unit 3014 is turned on and the first switching unit 3012 is not turned on.

[0069] Understandably, when the first switching unit 3012 is on and the second switching unit 3014 is off, it indicates that the first circuit loop is conducting. Furthermore, since the first circuit loop is conducting, it charges the first energy storage unit 3013, allowing it to store electrical energy. Understandably, since the second switching unit 3014 is off at this time, the voltage between the first output port 3017 and the second output port 3019 can be maintained by the second energy storage unit 3015.

[0070] It is also understood that when the second switching unit 3014 is turned on and the first switching unit 3012 is not turned on, it indicates that the second circuit loop is conductive. Furthermore, since the second circuit loop is conductive, it will charge the second energy storage unit 3015, thereby enabling the second energy storage unit 3015 to store electrical energy. And it is understood that in this embodiment, when the second circuit loop is turned on to charge the second energy storage unit 3015, the voltage on the second energy storage unit 3015 is equal to the voltage on the secondary winding 3011 plus the voltage on the first energy storage unit 3013.

[0071] It is understandable that in the prior art, the voltage on the second energy storage unit 3015 is entirely provided by the voltage on the secondary winding 3011. However, in this embodiment, since the first switching unit is on when the second switching unit is not conducting (i.e., it can charge the first energy storage unit 3013), in this case, when the second switching unit is on to charge the second energy storage unit 3015, if the voltage on the second energy storage unit 3015 that needs to be output is fixed, since a portion of the voltage can be provided by the first energy storage unit 3013, the voltage on the secondary winding 3011 when the primary switching tube is turned off can be reduced. Furthermore, since the voltage on the secondary winding 3011 is usually related to the number of turns of the secondary winding 3011, generally, the more voltage is required on the secondary winding 3011, the more turns the corresponding secondary winding 3011 will have. Therefore, in this embodiment, since the voltage on the secondary winding 3011 when the primary-side switch is turned off can be reduced, the number of turns in the secondary winding 3011 can be reduced, thereby reducing the problems of large transformer size and high cost. Furthermore, it also reduces the problem of poor EMI characteristics of the transformer.

[0072] It should be noted that the specific circuit structure in the primary-side circuit 302 is not limited in this embodiment and can be determined according to the actual scenario.

[0073] In one possible implementation, the first energy storage unit includes at least one first capacitor, the second energy storage unit includes at least one second capacitor, the first switching unit is a first diode, the second switching unit is a second diode, and the negative terminal of the first diode is connected to the positive terminal of the second diode.

[0074] For example, Figure 4 A schematic diagram of the circuit structure of a voltage conversion unit provided in another embodiment of this application. For example... Figure 4 As shown, the voltage conversion unit includes a secondary circuit 401, a primary circuit 402, and a transformer. The transformer includes a winding 4011 in the secondary circuit 401, a winding 4021 in the primary circuit 402, and an iron core. It should be noted that in this embodiment, winding 4011 is also referred to as the secondary winding 4011.

[0075] Specifically, the primary circuit includes a switching transistor 4022. The secondary circuit 401 includes a first circuit loop, which contains a secondary winding 4011, a first diode 4012, and a first capacitor 4013.

[0076] The secondary circuit 401 also includes a second circuit loop, which includes a secondary winding 4011, a second diode 4014, and a second capacitor 4015. The secondary circuit 401 also includes a first output port 4017 and a second output port 4019. The first output port 4017 is connected to the first port 4016 of the second capacitor 4015, and the second output port 4019 is connected to the second port 4018 of the second capacitor 4015. When the switching transistor 4022 is turned on, the first switching unit 4012 is turned on and the second switching unit 4015 is not turned on. When the switching transistor 4022 is turned off, the second switching unit 4015 is turned on and the first switching unit 4012 is not turned on.

[0077] Compared with this embodiment Figure 3 In the embodiment shown, a first diode 4012 is used as a first switching unit, a second diode 4014 is used as a second switching unit, a first capacitor 4013 is used as a first energy storage unit, a second capacitor 4015 is used as a second energy storage unit, and the negative terminal of the first diode is connected to the positive terminal of the second diode.

[0078] In this embodiment, when the switch 4022 in the primary circuit is turned on, the first diode 4012 is turned on and the second diode 4014 is not turned on. When the switch 4022 in the primary circuit is turned off, the second diode 4014 is turned on and the first diode 4012 is not turned on.

[0079] like Figure 4 As shown, when the first diode 4012 is conducting and the second diode 4014 is not conducting, it indicates that the first circuit loop is conducting. At this time, the current flow in the first current loop is as follows: starting from the lower end of the secondary winding 4011, flowing through the first diode 4012, then through the first capacitor 4013, and finally returning to the upper end of the secondary winding 4011. This charges the first capacitor 4013, allowing it to store electrical energy. Furthermore, since the second diode 4014 is not conducting at this time, the voltage between the first output port 4017 and the second output port 4019 can be maintained by the second capacitor 4015.

[0080] It is also understandable that when the second diode 4014 is conducting and the first diode 4012 is not conducting, it indicates that the second circuit loop is conducting. At this time, the current flow in the second current loop is as follows: starting from the upper end of the secondary winding 4011, flowing through the first diode 4012, then through the second diode 4014, then through the second capacitor 4015, and finally returning to the lower end of the secondary winding 4011. This will charge the second capacitor 4015.

[0081] Furthermore, it is understood that in this embodiment, when the second capacitor 4015 is charged, the voltage on the second capacitor 4015 is equal to the voltage on the secondary winding 4011 when the primary-side switch is off plus the voltage on the first capacitor 4013 when the primary-side switch is on. Therefore, if the voltage on the second capacitor 4015 to be output is fixed, since a portion of the voltage can be shared by the first capacitor 4013, the voltage on the secondary winding 4011 when the primary-side switch is off can be reduced. This reduces the number of turns in the secondary winding 4011, thereby reducing the problems of large transformer size and high cost. Furthermore, it reduces the problem of poor EMI characteristics of the transformer.

[0082] As an optional embodiment, the first circuit loop further includes at least one current-limiting element, which is connected in series with the first diode and the first energy storage unit. Exemplarily, the current-limiting element includes any one of the following: a resistor, an inductor, or a thermistor.

[0083] It should be understood that the circuit conversion unit in this application may be included in the inverter. In this case, the inverter in this application can also be used to repair the PID generated by the photovoltaic module. Specifically, when used to repair the PID, the first output port in this embodiment can be used to connect to the negative terminal (PV-) of the photovoltaic module, and the second output port is used to ground.

[0084] It should also be noted that the secondary circuit of the inverter in this application may include more branches, such as branches for other applications (e.g., power supply), such as the main feedback branch. The main feedback branch can be considered as a branch that requires a relatively stable output voltage and high precision.

[0085] Below, in conjunction with Figure 5 Specifically, this application explains why the voltage conversion unit provided in this application can reduce the number of turns on the secondary winding.

[0086] Figure 5 This is a structural schematic diagram of a voltage conversion unit provided in yet another embodiment of this application. Wherein, in Figure 5 In this diagram, the circuit on the left represents the primary circuit. The circuit connected to the primary winding includes a switching transistor Q1, and the winding in the primary circuit is called L1. For ease of description, this embodiment also refers to the switching transistor Q1 as the primary switching transistor Q1. In this embodiment, the secondary circuit on the right includes two branches: a main feedback branch and a branch used to repair the PID controller.

[0087] In this embodiment, the winding in the main feedback branch is referred to as L2. Specifically, the main feedback branch includes diode D3 and capacitor C3. In this embodiment, the output voltage of capacitor C3 is represented by Vout.

[0088] The winding in the branch used for PID repair is called L3. Specifically, the branch used for PID repair includes diode D1, resistor Z1, capacitor C1, diode D2, and capacitor C2. One end of capacitor C2 outputs a positive voltage (PID+ in the diagram), and the other end is connected to ground. The connection relationships between each component can be found in [reference needed]. Figure 5 .

[0089] for Figure 5 In the voltage conversion unit shown, during the conduction of the primary-side switch Q1, the winding L1 in the primary circuit is in a state where the upper terminal is positive and the lower terminal is negative. At this time, the transformer is in the magnetization stage, and the current continuously increases. For the main feedback branch in the secondary circuit, diode D3 is reverse-biased and there is no current in the winding L2 in the main feedback branch. For the branch used to repair the PID, diode D1 is forward-biased, and current flows through winding L3, resistor Z1, diode D1, and capacitor C1. During this period, capacitor C1 is charged, and the voltage of capacitor C1 is in a state where the left side is negative and the right side is positive. However, for the diode D2 in the branch used to repair the PID, it is reverse-biased and the PID output voltage is mainly maintained by capacitor C2.

[0090] During the off-side period of the primary-side switch Q1, the winding L1 in the primary circuit is in a state where the upper terminal is negative and the lower terminal is positive, and the current is 0. At this time, the transformer is in the demagnetizing stage. For the secondary-side circuit, the winding L2 in the main feedback branch is in a state where the upper terminal is positive and the lower terminal is negative. At this time, diode D3 is forward-biased, charging capacitor C3 in the main feedback branch. For the branch used to repair the PID, the winding L3 is in a state where the upper terminal is positive and the lower terminal is negative. At this time, diode D1 is reverse-biased and diode D2 is forward-biased. The current in the branch used to repair the PID flows through winding L3, capacitor C1, diode D2, and capacitor C2. It can be seen that the PID output voltage at this time is equal to the voltage on winding L3 during the Q1 off-side period plus the voltage on capacitor C1 when Q1 is on.

[0091] Now, assume the primary winding L1 has N1 turns, the input voltage of the primary circuit is Vin, the winding L2 in the main feedback branch has N2 turns, and the output voltage of the main feedback branch is Vout (i.e., the voltage across capacitor C3). The winding L3 in the branch used to repair the PID controller has N3 turns, and the output voltage of the branch used to repair the PID controller is Vpid (i.e., the voltage across capacitor C2). Then, during the conduction of the primary-side switch Q1, the induced voltage corresponding to the winding L3 in the branch used to repair the PID controller is: Vin N3 / N1; while during the turn-off period of the primary-side switch Q1, the induced voltage corresponding to the winding L3 in the branch used to repair the PID is: Vout N3 / N2; therefore, we can conclude that: Vpid = Vin N3 / N1+ Vout N3 / N2.

[0092] It is understandable that since the anti-PID voltage is numerically equal to the voltage on capacitor C1 when the primary-side switch Q1 is turned on plus the voltage on winding L3 when the primary-side switch Q1 is turned off, the number of turns of winding L3 can be reduced, thereby reducing the size of the transformer and improving the EMI characteristics of the transformer.

[0093] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more sets of available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium. A semiconductor medium can be a solid-state drive.

[0094] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0095] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0096] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0097] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0098] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0099] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0100] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0101] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0102] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory, random access memory, magnetic disks, or optical disks.

[0103] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A device for repairing the potential-induced degradation effect of a photovoltaic module, characterized in that, The repair device includes a transformer, a primary circuit, and a secondary circuit. The primary circuit includes a switching transistor, and the secondary circuit includes a first circuit loop, which contains the secondary winding of the transformer, a first switching unit, and a first energy storage unit. The secondary circuit also includes a second circuit loop, which includes the secondary winding of the transformer, the first energy storage unit, the second switching unit, and the second energy storage unit. The positive terminal of the second energy storage unit is used to connect to the negative terminal of the photovoltaic module in the photovoltaic power generation system, and the negative terminal of the second energy storage unit is used to connect to the ground. When the switch tube is turned on, the first switch unit is turned on and the second switch unit is not turned on, and the first circuit loop is in a conducting state. When the switch tube is turned off, the second switch unit is turned on and the first switch unit is not turned on, and the second circuit loop is in a conducting state.

2. The repair device according to claim 1, characterized in that, The first energy storage unit includes at least one first capacitor.

3. The repair device according to claim 1 or 2, characterized in that, The second energy storage unit includes at least one second capacitor.

4. The repair device according to claim 1 or 2, characterized in that, The first switching unit is a first diode, and the second switching unit is a second diode.

5. The repair device according to claim 4, characterized in that, The negative terminal of the first diode is connected to the positive terminal of the second diode.

6. The repair device according to claim 4, characterized in that, The first circuit loop further includes at least one current limiting element, which is connected in series with the first diode and the first energy storage unit.

7. The repair device according to claim 6, characterized in that, The current-limiting element includes any one of the following: resistor, inductor, or thermistor.

8. An inverter, characterized in that, Includes the repair device as described in any one of claims 1 to 7.

9. A photovoltaic power generation system, characterized in that, Including the inverter as described in claim 8.

10. A voltage conversion unit, characterized in that, The voltage conversion unit includes a transformer, a primary circuit, and a secondary circuit. The primary circuit includes a switching transistor, and the secondary circuit includes a first circuit loop, which includes the secondary winding of the transformer, a first switching unit, and a first energy storage unit. The secondary circuit also includes a second circuit loop, which includes the secondary winding of the transformer, the first energy storage unit, the second switching unit, and the second energy storage unit. The secondary circuit also includes a first output port and a second output port, wherein the first output port is connected to the first port of the second energy storage unit, and the second output port is connected to the second port of the second energy storage unit; When the switching transistor is turned on, the first switching unit is turned on and the second switching unit is not turned on, and the first circuit loop is in a conducting state. When the switching transistor is turned off, the second switching unit is turned on and the first switching unit is not turned on, and the second circuit loop is in a conducting state.

11. The voltage conversion unit according to claim 10, characterized in that, The first energy storage unit includes at least one first capacitor.

12. The voltage conversion unit according to claim 10 or 11, characterized in that, The second energy storage unit includes at least one second capacitor.

13. The voltage conversion unit according to claim 10 or 11, characterized in that, The first switching unit is a first diode, and the second switching unit is a second diode.

14. The voltage conversion unit according to claim 13, characterized in that, The negative terminal of the first diode is connected to the positive terminal of the second diode.

15. The voltage conversion unit according to claim 13, characterized in that, The first circuit loop further includes at least one current limiting element, which is connected in series with the first diode and the first energy storage unit.

16. The voltage conversion unit according to claim 15, characterized in that, The current-limiting element includes any one of the following: resistor, inductor, or thermistor.

17. An inverter, characterized in that, Includes a voltage conversion unit as described in any one of claims 10 to 16.

18. The inverter according to claim 17, characterized in that, The inverter is also used to repair potential-induced degradation (PID) caused by photovoltaic modules.

19. The inverter according to claim 18, characterized in that, The first output port is used to connect to the negative terminal of the photovoltaic module, and the second output port is used to connect to ground.

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