Power converter

Abstract

The invention provides a power converter, and belongs to the technical field of power electronics. In the scheme provided by the invention, the lightning protection unit in the power converter comprises a piezoresistor and a gas discharge tube which are connected in series. Therefore, the action voltage of the lightning protection unit can be effectively increased on the premise that the action voltage of the piezoresistor is not increased, and it is ensured that the lightning protection unit can be suitable for the high-voltage power converter. Moreover, by connecting the divider resistor in parallel with the gas discharge tube, flexible voltage division of the piezoresistor and the gas discharge tube can be realized, so that the model selection flexibility of the piezoresistor and the gas discharge tube is effectively improved. Besides, in a lightning stroke scene, the voltage at the two ends of the gas discharge tube after action is relatively low, and the residual voltage of the lightning protection unit can be prevented from being increased, so that the requirement on the protection performance of each power device in the power converter can be prevented from being increased.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a power converter. Background Technology

[0002] Power converters are core equipment in new energy power generation systems. Taking photovoltaic (PV) power generation systems as an example, the power converter used in PV systems is a PV inverter, which converts the direct current (DC) from PV modules into alternating current (AC) before outputting it to the power grid. To ensure the safe operation of the power converter, lightning protection devices need to be installed at both the DC and AC terminals of the power converter.

[0003] Lightning protection devices typically include one or more varistors connected between the power line and the ground wire. When a power converter is struck by lightning, causing a momentary high voltage on the power line, and this momentary high voltage exceeds the operating voltage of the varistor, the resistance of the varistor will drop instantaneously, thereby dissipating the lightning energy to the ground wire in a timely manner. To prevent varistor malfunction, the operating voltage of the varistor must be greater than the operating voltage of the power converter during normal operation.

[0004] To accommodate power converters with higher operating voltages, the operating voltage of the varistor also needs to be increased accordingly. However, varistors with higher operating voltages are not only more expensive, but also have less flexibility in selection. Summary of the Invention

[0005] This application provides a power converter that can solve the technical problems of high cost and low selection flexibility of varistors used in high-voltage power converters.

[0006] Firstly, a power converter is provided. The power converter includes a power conversion circuit, multiple first surge protection units, and second surge protection units. The DC terminal of the power conversion circuit is used to connect to a photovoltaic module or energy storage battery, and the AC terminal is used to connect to the power grid or a load. The power conversion circuit converts the DC power from the photovoltaic module or energy storage battery into AC power for output. The first terminals of the multiple first surge protection units are connected one-to-one with the three phase lines of the AC terminal, and the second terminals of the multiple first surge protection units are connected to a first node. Furthermore, each first surge protection unit includes a first varistor and a first gas discharge tube connected in series, and a first voltage divider resistor connected in parallel with the first gas discharge tube. The first terminal of each second surge protection unit is connected to the first node, and the second terminal of each second surge protection unit is used for grounding. Furthermore, each second surge protection unit includes a second varistor.

[0007] By connecting a gas discharge tube in series with the varistor, the operating voltage of the surge protection unit can be effectively increased without increasing the operating voltage of the varistor, thus ensuring that the surge protection unit can be used with high-voltage power converters. Furthermore, after connecting the first voltage-dividing resistor in parallel with the gas discharge tube, the voltage division ratio of the first varistor is rv1 / (rv1+r1), and the voltage division ratio of the first gas discharge tube is r1 / (rv1+r1). Here, r1 is the resistance value of the first voltage-dividing resistor, and rv1 is the resistance value of the first varistor. Therefore, by flexibly adjusting the resistance value r1 of the first voltage-dividing resistor, flexible voltage division of the varistor and gas discharge tube can be achieved, thereby effectively improving the selection flexibility of the varistor and gas discharge tube and ensuring that the cost of both the varistor and gas discharge tube remains low. Furthermore, in lightning strike scenarios, since the voltage across the gas discharge tube is low (e.g., approximately 0) after it activates, the series-connected gas discharge tube will not increase the residual voltage of the lightning protection unit, thus not increasing the protection performance requirements of each power device in the power converter, ensuring that even power converters with higher operating voltages can maintain lower costs.

[0008] In one possible implementation, the first surge protection unit further includes a second voltage-dividing resistor connected in parallel with the first varistor. Since the resistance of the varistor in the surge protection unit is typically much larger than the resistance of the voltage-dividing resistor, connecting the first varistor in parallel with the second voltage-dividing resistor ensures that the equivalent resistance of the first varistor and the second voltage-dividing resistor in parallel is approximately equal to the resistance of the second voltage-dividing resistor. Accordingly, the voltage division ratio of the first varistor is r2 / (r1+r2), and the voltage division ratio of the first gas discharge tube is r1 / (r1+r2). Here, r2 is the resistance of the second voltage-dividing resistor. Therefore, by flexibly adjusting the resistance values ​​r1 of the first voltage-dividing resistor and r2 of the second voltage-dividing resistor, the voltage division ratio of the varistor and the gas discharge tube can be flexibly adjusted. Furthermore, compared to a scheme where the varistor is not connected in parallel with the voltage-dividing resistor, the adjustable range of the voltage division ratio of the varistor and the gas discharge tube is larger after connecting the varistor in parallel with the voltage-dividing resistor, thereby further improving the selection flexibility of the varistor and the gas discharge tube.

[0009] In one possible implementation, the resistance value of the second voltage divider resistor is greater than the resistance value of the first voltage divider resistor, that is, the voltage division ratio of the first varistor is greater than the voltage division ratio of the first gas discharge tube.

[0010] In power converters with low operating voltages, surge protection units are typically implemented using varistors. Therefore, the operating voltage of the varistor in the surge protection unit is selected based on the lower operating voltage. For power converters with higher operating voltages, since the first surge protection unit is formed by connecting a first varistor and a first gas discharge tube in series, the operating voltages of the first varistor and the first gas discharge tube are selected based on the higher operating voltage. In the solution provided in this application, the operating voltage of the first varistor can continue to be selected based on the lower operating voltage, thereby reducing the complexity of selecting the first varistor. Correspondingly, the operating voltage of the first gas discharge tube can be selected based on the voltage difference between the higher and lower operating voltages. Since the voltage difference is usually less than the lower operating voltage, the voltage division ratio of the first gas discharge tube can be less than the voltage division ratio of the first varistor.

[0011] In one possible implementation, the second lightning protection unit further includes: a second gas discharge tube connected in series with the second varistor, a third voltage divider resistor connected in parallel with the second varistor, and a fourth voltage divider resistor connected in parallel with the second gas discharge tube.

[0012] The second surge protection unit also employs a series connection of a varistor and a gas discharge tube. This effectively increases the operating voltage of the second surge protection unit without increasing the operating voltage of the varistor or its residual voltage. On one hand, this ensures the second surge protection unit is suitable for high-voltage power converters; on the other hand, it avoids increasing the protection requirements for the power devices in the power converter. Furthermore, by connecting voltage-dividing resistors in parallel to the varistor and gas discharge tube in the second surge protection unit, flexible voltage division can be achieved, thereby effectively improving the selection flexibility of the varistor and gas discharge tube and ensuring that the cost of both varistor and gas discharge tube in the second surge protection unit remains low.

[0013] In one possible implementation, the resistance value of the third voltage divider resistor is greater than the resistance value of the fourth voltage divider resistor, that is, the voltage division ratio of the second varistor is greater than the voltage division ratio of the second gas discharge tube.

[0014] In the solution provided in this application, the operating voltage of the second varistor can continue to be selected based on the lower operating voltage, while the operating voltage of the second gas discharge tube is selected based on the voltage difference between the higher and lower operating voltages. This effectively reduces the complexity of selecting the second varistor.

[0015] In one possible implementation, the power converter further includes multiple third and fourth surge protection units. The first terminals of the multiple third surge protection units are connected to the positive and negative terminals of the DC terminal respectively, and the second terminals of the multiple third surge protection units are connected to a second node. Furthermore, the structure of the third surge protection unit is the same as that of the first surge protection unit. The first terminal of the fourth surge protection unit is connected to the second node, and the second terminal of the fourth surge protection unit is used for grounding. Furthermore, the structure of the fourth surge protection unit is the same as that of the second surge protection unit.

[0016] By also installing a surge protection unit at the DC end of the power converter, effective surge protection for the DC end can be achieved. Furthermore, the surge protection unit at the DC end is formed by connecting a varistor and a gas discharge tube in series. This effectively increases the operating voltage of the surge protection unit at the DC end without increasing the operating voltage of the varistor or the residual voltage of the surge protection unit. On the one hand, this ensures that the surge protection unit at the DC end is suitable for high-voltage power converters; on the other hand, it avoids increasing the protection requirements for the power devices in the power converter. In addition, by connecting a voltage divider resistor in parallel to the gas discharge tube in the surge protection unit at the DC end, flexible voltage division between the varistor and the gas discharge tube can be achieved, thereby effectively improving the selection flexibility of the varistor and gas discharge tube in the surge protection unit at the DC end.

[0017] In one possible implementation, the power converter includes a greater number of fourth surge protection units than the second surge protection units. For example, the power converter includes two fourth surge protection units and one second surge protection unit.

[0018] In scenarios where the power converter is a photovoltaic (PV) inverter, the DC terminal of the PV inverter is typically connected to a large number of PV modules. The resulting inductance loop has a large area, leading to a significant amount of lightning strike energy at the DC terminal. Therefore, by installing a large number of fourth surge protection units at the DC terminal to distribute the lightning strike energy, the reliability and lightning protection performance of the DC terminal surge protection units can be ensured.

[0019] In one possible implementation, the power conversion circuit includes a DC / DC conversion circuit and a DC / AC conversion circuit. Furthermore, the power converter also includes multiple fifth and sixth surge protection units. The DC / DC conversion circuit is connected to the DC / AC conversion circuit via a DC bus. The first terminals of the multiple fifth surge protection units are connected to both the positive and negative buses of the DC bus, and the second terminals of the multiple fifth surge protection units are connected to a third node. The structure of the fifth surge protection unit is the same as that of the first surge protection unit. The first terminal of the sixth surge protection unit is connected to the third node, and the second terminal of the sixth surge protection unit is used for grounding. The structure of the sixth surge protection unit is the same as that of the second surge protection unit.

[0020] By connecting a surge protection unit to the DC bus as well, effective surge protection for the DC bus can be achieved. Furthermore, the surge protection unit connected to the DC bus has the same structure as the surge protection unit at the AC end, which can effectively increase the operating voltage of the surge protection unit without increasing the operating voltage of the varistor or the residual voltage of the surge protection unit, and effectively improve the selection flexibility of the varistor and gas discharge tube in the surge protection unit.

[0021] In one possible implementation, the resistance values ​​of the first, second, third, and fourth voltage divider resistors in the power converter are all greater than or equal to 1 megohm (MΩ). By setting the resistance values ​​of each voltage divider resistor to be relatively high, it can be ensured that the current flowing through the voltage divider resistors is small during normal operation of the power converter, thereby avoiding affecting the normal operation of the power converter.

[0022] Secondly, another power converter is provided, including: a power conversion circuit, multiple third surge protection units, and a fourth surge protection unit. The DC terminal of the power conversion circuit is used to connect to photovoltaic modules or energy storage batteries, and the AC terminal is used to connect to the power grid or load. The power conversion circuit converts the DC power from the photovoltaic modules or energy storage batteries into AC power for output. The first terminals of the multiple third surge protection units are connected to the positive and negative terminals of the DC terminal, respectively, and the second terminals of the multiple third surge protection units are connected to a second node. Each third surge protection unit includes: a first varistor and a first gas discharge tube connected in series, and a first voltage divider resistor connected in parallel with the first gas discharge tube. The first terminal of the fourth surge protection unit is connected to the second node, and the second terminal of the fourth surge protection unit is used for grounding. The fourth surge protection unit includes a second varistor.

[0023] In one possible implementation, the third lightning protection unit further includes a second voltage divider resistor connected in parallel with the first varistor.

[0024] In one possible implementation, the resistance value of the second voltage divider resistor is greater than the resistance value of the first voltage divider resistor.

[0025] In one possible implementation, the fourth lightning protection unit further includes: a second gas discharge tube connected in series with the second varistor, a third voltage divider resistor connected in parallel with the second varistor, and a fourth voltage divider resistor connected in parallel with the second gas discharge tube.

[0026] In one possible implementation, the resistance value of the third voltage divider resistor is greater than the resistance value of the fourth voltage divider resistor.

[0027] In one possible implementation, the resistance values ​​of the first, second, third, and fourth voltage divider resistors in the power converter are all greater than or equal to 1 megohm.

[0028] The technical effects of the power converter and its various implementations provided in the second aspect above can be referred to the corresponding effect descriptions in the power converter provided in the first aspect above, and will not be repeated here.

[0029] In summary, this application provides a power converter. The surge protection unit in this power converter includes a varistor and a gas discharge tube connected in series. Because the gas discharge tube has low cost and high withstand voltage, the operating voltage of the surge protection unit can be effectively increased without increasing the operating voltage of the varistor, ensuring that the surge protection unit is suitable for high-voltage power converters. Furthermore, by connecting a voltage divider resistor in parallel to the gas discharge tube, flexible voltage division between the varistor and the gas discharge tube can be achieved, thereby effectively improving the selection flexibility of the varistor and the gas discharge tube, and ensuring that the cost of the varistor and the gas discharge tube can be kept low. In addition, in a lightning strike scenario, the voltage across the gas discharge tube after activation is low (e.g., approximately 0), which avoids increasing the residual voltage of the surge protection unit, thereby avoiding increasing the protection performance requirements of the power devices in the power converter. Attached Figure Description

[0030] Figure 1 This is a network diagram of a photovoltaic energy storage system provided in an embodiment of this application;

[0031] Figure 2 This is a schematic diagram of the structure of a photovoltaic inverter provided in an embodiment of this application;

[0032] Figure 3 This is a schematic diagram of the structure of a power converter provided in an embodiment of this application;

[0033] Figure 4 This is a schematic diagram of another power converter provided in an embodiment of this application;

[0034] Figure 5 This is a schematic diagram of another power converter provided in the embodiments of this application;

[0035] Figure 6 This is a schematic diagram of another power converter provided in the embodiments of this application;

[0036] Figure 7 This is a schematic diagram of another power converter provided in the embodiments of this application;

[0037] Figure 8 This is a schematic diagram of another power converter provided in the embodiments of this application;

[0038] Figure 9 This is a schematic diagram of another power converter provided in the embodiments of this application. Detailed Implementation

[0039] The power converter provided in the embodiments of this application is described in detail below with reference to the accompanying drawings. First, the key terms involved in the embodiments of this application are introduced.

[0040] A power converter is a power electronic device that converts electrical energy into its current form by switching power devices (also called switching transistors) on and off. Power converters typically include photovoltaic inverters and power conversion systems (PCS). Photovoltaic inverters convert direct current (DC) from photovoltaic modules into alternating current (AC) for transmission to the grid. Power conversion systems convert DC from energy storage batteries into AC for transmission to the grid; additionally, they can convert AC from the grid into DC and charge the energy storage batteries.

[0041] Common-mode lightning strike: The lightning current flows between the power converter's port (e.g., DC or AC terminal) and ground. For example, for the DC terminal of the power converter, the differential-mode lightning strike current flows between the positive terminal PV+ and ground, or between the negative terminal PV-. For the AC terminal of the power converter, the differential-mode lightning strike current flows between the phase line and ground.

[0042] Differential-mode lightning strike: The lightning current flows between the ports of the power converter. For example, for the DC terminal of the power converter, the differential-mode lightning current flows between the positive (PV+) and negative (PV-) terminals. For the AC terminal of the power converter, the differential-mode lightning current flows between the different phase lines.

[0043] Figure 1 This is a network diagram of a photovoltaic energy storage system provided in an embodiment of this application. Figure 1 As shown, the photovoltaic-storage system includes a photovoltaic inverter and an energy storage converter. Photovoltaic modules convert solar energy into direct current (DC) through the photovoltaic effect. The photovoltaic inverter converts the DC output from the photovoltaic modules into alternating current (AC) and further transmits the AC to a prefabricated substation. The prefabricated substation converts the low-voltage AC output from the photovoltaic inverter into medium-voltage AC and further transmits the AC to a step-up substation (grid). When there is excess electricity generated by the photovoltaic modules, the energy storage system stores the unstable electricity from the photovoltaic modules and outputs stable electricity to the grid through the energy storage converter and the corresponding prefabricated substation. In addition, when the grid electricity price is low, the energy storage converter can also convert the grid's AC to DC to charge the energy storage system. It is worth noting that in the photovoltaic-storage system, the photovoltaic inverter and the energy storage converter can be collectively referred to as a power converter. The power converter provided in this application embodiment can be applied not only to photovoltaic-storage systems but also to power supply systems such as photovoltaic power generation systems or energy storage systems.

[0044] To ensure the safe operation of power supply systems (such as photovoltaic power generation systems), power converters need to be equipped with surge protection devices on both the AC and DC ends. Typically, surge protection devices are implemented using varistors connected in series, thereby achieving common-mode and differential-mode surge protection capabilities for the power converter. For example, taking a photovoltaic inverter as an example... Figure 2 As shown, the power conversion circuit in the photovoltaic inverter is equipped with a DC-side surge protection device on the DC side and an AC-side surge protection device on the AC side. The AC-side surge protection device includes four surge protection modules. Each of the three phase lines (L1, L2, and L3) on the AC side is connected to one surge protection module to a common node N1, and then another surge protection module is connected from the common node N1 to ground. The DC-side surge protection device includes three surge protection modules connected in a Y-type configuration. The positive terminal PV+ and the negative terminal PV- on the DC side are each connected to one surge protection module to a common node N2, and then another surge protection module is connected from the common node N2 to ground. Each surge protection module is typically formed by encapsulating one or more varistors.

[0045] When the DC or AC terminals of the power converter are struck by lightning, causing the voltage across the surge protection module to exceed its operating voltage, the module's resistance will drop sharply, thus dissipating the lightning energy to ground. Furthermore, the surge protection module can clamp the voltage across its terminals to the clamping voltage to achieve overvoltage protection. The operating voltage, also known as the breakdown voltage or reference voltage, is the threshold voltage at which the resistance of the surge protection module begins to change sharply. The clamping voltage, also known as the limiting voltage or residual voltage, is the maximum voltage value across the surge protection module when it is subjected to an inrush current (such as a lightning strike current).

[0046] During normal operation of the power converter, to prevent malfunction of the surge protection module, the operating voltage of the surge protection module in the DC-side surge protection device must be greater than the maximum operating voltage of the DC terminal of the power converter during normal operation; for example, it must be greater than the string voltage of the photovoltaic string connected to the DC terminal. Similarly, the operating voltage of the surge protection module in the AC-side surge protection device must be greater than the maximum operating voltage of the AC terminal of the power converter; for example, it must be greater than the AC grid voltage. To achieve effective protection of the power converter, the residual voltage must be less than or equal to the maximum withstand voltage of each power device in the power converter to prevent the power devices from being damaged by lightning surges.

[0047] With the increasing pursuit of power generation efficiency and system cost reduction in power supply systems such as photovoltaic power generation systems, the system voltage of power supply systems is becoming increasingly higher. This system voltage includes the operating voltage of the DC and AC terminals of the power converter. To adapt to the higher system voltage, the operating voltage of the varistor in the surge protection module needs to be increased, i.e., the withstand voltage rating of the varistor needs to be increased. However, varistors with higher operating voltages are more expensive and have less selection flexibility. Furthermore, the residual voltage after a varistor with a higher operating voltage is higher, which places higher demands on the protection performance of each power device in the power converter, i.e., the maximum withstand voltage of each power device also needs to be higher. This further increases the design complexity and hardware cost of the power converter.

[0048] Figure 3 This is a schematic diagram of a power converter provided in an embodiment of this application. The power converter can be a photovoltaic inverter or an energy storage converter, etc. The following description uses a photovoltaic inverter as an example. When the power converter is an energy storage converter, the embodiments of this application are equally applicable and will not be elaborated upon here. Figure 3 As shown, the photovoltaic inverter provided in this embodiment includes a power conversion circuit 10 and an AC-side surge protection device 20. The AC-side surge protection device 20 includes multiple first surge protection units 21 and second surge protection units 22. For example, Figure 3 The diagram shows three first lightning protection units 21 and one second lightning protection unit 22.

[0049] The power conversion circuit 10 has a DC terminal for connecting to photovoltaic modules. For example, the DC terminal of the power conversion circuit 10 is used to connect to at least one photovoltaic string, each photovoltaic string including multiple photovoltaic modules connected in series. The AC terminal of the power conversion circuit 10 is used to connect to the power grid or a load. This power conversion circuit 10 is used to convert the DC power from the photovoltaic modules into AC power for output.

[0050] refer to Figure 3 and Figure 4 Each of the multiple first surge protection units 21 has its first terminal connected to one of the three phase lines of the AC terminal of the power conversion circuit 10, and its second terminal connected to the first node N1. For example, the AC terminal of the power conversion circuit 10 includes three phase lines: L1, L2, and L3. The photovoltaic inverter includes three first surge protection units 21 corresponding to these three phase lines, with the first terminal of each first surge protection unit 21 connected to a corresponding phase line. (Reference) Figure 5 Each first lightning protection unit 21 includes: a first varistor RV1 and a first gas discharge tube G1 connected in series, and a first voltage divider resistor R1 connected in parallel with the first gas discharge tube G1.

[0051] refer to Figures 3 to 5The first end of the second lightning protection unit 22 is connected to the first node N1, and the second end of the second lightning protection unit 22 is used for grounding. Furthermore, as... Figure 5 As shown, the second lightning protection unit 22 includes a second varistor RV2, one end of which is connected to the first node N1, and the other end is used for grounding.

[0052] In this embodiment, after connecting the first gas discharge tube G1 and the first varistor RV1 in series, the operating voltage of the first surge protection unit 21 is the sum of the operating voltages of the first gas discharge tube G1 and the first varistor RV1. Furthermore, after the first gas discharge tube G1 operates, i.e., after it is broken down, the voltage across it is low (e.g., approximately 0). Therefore, connecting the first varistor RV1 in series with the first gas discharge tube G1 does not increase the residual voltage of the first surge protection unit 21, thus avoiding increasing the protection requirements for the power devices in the photovoltaic inverter. In addition, since a voltage divider resistor is connected in parallel with the first gas discharge tube G1, the voltage division ratio between the first varistor RV1 and the first gas discharge tube G1 can be flexibly adjusted by adjusting the resistance value of the voltage divider resistor. For example, the voltage division ratio k1 of the first varistor RV1 can satisfy: k1 = rv1 / (rv1 + r1), and the voltage division ratio k2 of the first gas discharge tube G1 can satisfy: k2 = r1 / (rv1 + r1). Where rv1 is the resistance value of the first varistor RV1, and r1 is the resistance value of the first voltage divider resistor R1. Both k1 and k2 are numbers greater than 0 and less than 1, and k1 + k2 = 1.

[0053] refer to Figures 3 to 5 It can be seen that two first surge protection units 21 are connected in series between every two phase lines at the AC terminal of the power conversion circuit 10. Since the connection loop between two phase lines is also called the differential-mode loop at the AC terminal, it can also be understood that two first surge protection units 21 are connected in series in the differential-mode loop at the AC terminal of the power conversion circuit 10, and these two first surge protection units 21 can protect against differential-mode lightning strikes. Furthermore, during normal operation of the power conversion circuit 10, these two first surge protection units 21 must withstand the AC voltage at the AC terminal of the power conversion circuit 10 to prevent malfunction of the surge protection units during normal operation. For example, the two first surge protection units 21 connected in series between every two phase lines must withstand the line voltage U between the phase lines. L That is, the sum of the operating voltages of the two first lightning protection units 21 must be greater than the line voltage U between the two phase lines. L Since the two first surge protection units 21 have the same structure, the operating voltage of each first surge protection unit 21 must be greater than the line voltage U. L 1 / 2, that is, greater than U L / 2. Accordingly, when selecting the first varistor RV1, it is necessary to ensure that its operating voltage is greater than k1×U. L / 2, When selecting the first gas discharge tube G1, it is necessary to ensure that its operating voltage is greater than k2×U. L / 2.

[0054] Based on the above analysis, it can be seen that connecting the first gas discharge tube G1 and the first varistor RV1 in series can effectively increase the operating voltage of the first surge protection unit 21 without increasing the operating voltage of the first varistor RV1 or the residual voltage of the first surge protection unit 21. This ensures that the first surge protection unit 21 is compatible with photovoltaic inverters with higher operating voltages. Furthermore, since the voltage division ratio of the first gas discharge tube G1 and the first varistor RV1 can be flexibly adjusted by flexibly designing the resistance value of the first voltage divider resistor R1 in the first surge protection unit 21, the selection flexibility of the first gas discharge tube G1 and the first varistor RV1 is effectively improved. Therefore, even photovoltaic inverters with higher operating voltages can use gas discharge tubes and varistors with lower operating voltages and lower costs to form a surge protection unit.

[0055] In one possible implementation, such as Figure 5 As shown, the first lightning protection unit 21 also includes a second voltage divider resistor R2 connected in parallel with the first varistor RV1. Furthermore, from... Figure 5 It can be seen that the first varistor RV1 and the first gas discharge tube G1 are connected in series between their respective phase lines and the first node N1. Similarly, the second voltage divider resistor R2 and the first voltage divider resistor R1 are also connected in series between their respective phase lines and the first node N1. In other words, the two voltage divider resistors, after being connected in series, are connected in parallel across the two ends of the series-connected first varistor RV1 and the first gas discharge tube G1. Furthermore, the series connection point between the second voltage divider resistor R2 and the first voltage divider resistor R1 connects to the series connection point between the first varistor RV1 and the first gas discharge tube G1.

[0056] In this embodiment, the voltage division ratio k1 of the first varistor RV1 can satisfy: k1 = (rv1 / / r2) / (rv1 / / r2 + r1), and the voltage division ratio k2 of the first gas discharge tube G1 can satisfy: k2 = r1 / (rv1 / / r2 + r1). Here, r2 is the resistance value of the second voltage-dividing resistor R2, and rv1 / / r2 is the equivalent resistance value of the first varistor RV1 and the second voltage-dividing resistor R2 connected in parallel. Since the resistance value rv1 of the first varistor RV1 is usually much larger than the resistance value of the voltage-dividing resistor, for example, much larger than the resistance value r2 of the second voltage-dividing resistor R2, the above equivalent resistance value rv1 / / r2 is approximately equal to the resistance value r2 of the second voltage-dividing resistor R2. Accordingly, the above voltage division ratios k1 and k2 can be approximately expressed as: k1 = r2 / (r2 + r1), k2 = r1 / (r2 + r1).

[0057] Based on the above analysis, it can be seen that by connecting the first varistor RV1 in parallel with the second voltage-dividing resistor R2, the equivalent resistance value of the first varistor RV1 and the second voltage-dividing resistor R2 in parallel can be approximately equal to the resistance value of the second voltage-dividing resistor R2. Therefore, the voltage division ratio of the varistor and the gas discharge tube can be flexibly adjusted by flexibly adjusting the resistance values ​​of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2. Furthermore, compared to the scheme without the varistor connected in parallel with the voltage-dividing resistor, the adjustable range of the voltage division ratio of both the varistor and the gas discharge tube is larger after the varistor is connected in parallel with the voltage-dividing resistor, thereby further improving the flexibility of selecting varistor and gas discharge tube.

[0058] In one possible implementation, such as Figure 6 As shown, the second surge protection unit 22 further includes: a second gas discharge tube G2 connected in series with the second varistor RV2, a third voltage divider resistor R3 connected in parallel with the second varistor RV2, and a fourth voltage divider resistor R4 connected in parallel with the second gas discharge tube G2. That is, the second surge protection unit 22 can also adopt the same structure as the first surge protection unit 21.

[0059] In this embodiment, after connecting the second gas discharge tube G2 and the second varistor RV2 in series, the operating voltage of the second surge protection unit 22 is the sum of the operating voltages of the second gas discharge tube G2 and the second varistor RV2. Furthermore, connecting the second varistor RV2 in series with the second gas discharge tube G2 does not increase the residual voltage of the second surge protection unit 22, thus avoiding increasing the protection requirements for the power devices in the photovoltaic inverter. In addition, since the second varistor RV2 and the second gas discharge tube G2 are each connected in parallel with a voltage divider resistor, the voltage division ratio of the second varistor RV2 and the second gas discharge tube G2 can be flexibly adjusted by adjusting the resistance values ​​of the two voltage divider resistors. Specifically, since the resistance value r3 of the third voltage divider resistor R3 is usually much smaller than the resistance value of the second varistor RV2, the voltage division ratio k3 of the second varistor RV2 can satisfy: k3 = r3 / (r3 + r4), and the voltage division ratio k4 of the second gas discharge tube G2 can satisfy: k4 = r4 / (r3 + r4). r4 is the resistance value of the fourth voltage divider resistor R4. k3 and k4 are both numbers greater than 0 and less than 1, and k3 + k4 = 1.

[0060] refer to Figures 3 to 6It can also be seen that each phase line of the AC terminal of the power conversion circuit 10 is connected in series with a first surge protection unit 21 and a second surge protection unit 22 between them. Since the connection loop between the phase line and ground at the AC terminal is also called the common-mode loop at the AC terminal, it can also be understood that the common-mode loop at the AC terminal of the power conversion circuit 10 contains a first surge protection unit 21 and a second surge protection unit 22 connected in series. These one first surge protection unit 21 and one second surge protection unit 22 can protect against common-mode lightning strikes. Furthermore, during normal operation of the power conversion circuit 10, these one first surge protection unit 21 and one second surge protection unit 22 must withstand the AC voltage at the AC terminal of the power conversion circuit 10 to prevent malfunction of the surge protection units during normal operation. For example, the sum of the operating voltages of the one first surge protection unit 21 and one second surge protection unit 22 connected in series between each phase line and ground must also be greater than the aforementioned line voltage U. L For scenarios where the first surge protection unit 21 and the second surge protection unit 22 have the same structure, the operating voltage of each surge protection unit must be greater than the line voltage U. L 1 / 2, that is, greater than U L / 2. Accordingly, when selecting the second varistor RV2, it is necessary to ensure that its operating voltage is greater than k3×U. L / 2, When selecting the second gas discharge tube G2, it is necessary to ensure that its operating voltage is greater than k4×U L / 2.

[0061] Based on the above analysis, connecting the second gas discharge tube G2 and the second varistor RV2 in series can effectively increase the operating voltage of the second surge protection unit 22 without increasing the operating voltage of the second varistor RV2 or the residual voltage of the second surge protection unit 22. This ensures that the second surge protection unit 22 is compatible with photovoltaic inverters operating at higher voltages. Furthermore, because the voltage division ratio of the second gas discharge tube G2 and the second varistor RV2 can be flexibly adjusted by flexibly designing the resistance values ​​of the two voltage divider resistors in the second surge protection unit 22, the selection flexibility of the second gas discharge tube G2 and the second varistor RV2 is effectively improved. Therefore, even photovoltaic inverters operating at higher voltages can use gas discharge tubes and varistors with lower operating voltages and lower costs to form the second surge protection unit 22.

[0062] In one possible implementation, the second lightning protection unit 22 may not include the third voltage divider resistor R3, that is, the second varistor RV2 may not need to be connected in parallel with the voltage divider resistor.

[0063] In one possible implementation, the resistance values ​​of the first voltage divider resistor R1, the second voltage divider resistor R2, the third voltage divider resistor R3, and the fourth voltage divider resistor R4 are all greater than or equal to 1 MΩ. (Reference) Figure 5 and Figure 6It can be seen that in the differential mode circuit of the AC terminal in different first surge protection units 21, the first voltage divider resistor R1, the second voltage divider resistor R2, the third voltage divider resistor R3, and the fourth voltage divider resistor R4 are connected in series in the common mode circuit of the AC terminal. Based on this, the resistance values ​​of each voltage divider resistor are set to be relatively large, ensuring that the current flowing through the differential mode circuit and the current flowing through the common mode circuit of the AC terminal are both small when the photovoltaic inverter is operating normally, thus avoiding affecting the normal operation of the photovoltaic inverter.

[0064] In one possible implementation, the resistance value of the third voltage-dividing resistor R3 is greater than the resistance value of the fourth voltage-dividing resistor R4. Accordingly, the voltage division ratio k3 of the second varistor RV2 is greater than the voltage division ratio k4 of the second gas discharge tube G2.

[0065] In photovoltaic inverters with lower operating voltages, such as those with an AC line voltage of 800V and a phase voltage of 462V, the first surge protection unit 21 and the second surge protection unit 22 are typically implemented using varistors. Therefore, the operating voltage of the varistors in these two surge protection units is selected based on the lower voltage V1 (e.g., 680V). For photovoltaic inverters with higher operating voltages, such as those with an AC line voltage of 1000V, since both the first surge protection unit 21 and the second surge protection unit 22 are formed by connecting varistors and gas discharge tubes in series, the operating voltage of the varistors and the operating voltage of the gas discharge tubes in each surge protection unit are selected based on the higher voltage V2 (e.g., 850V).

[0066] In this embodiment, the specifications of the second varistor RV2 can continue to be the same as those in the photovoltaic inverter with a lower operating voltage; that is, the operating voltage of the second varistor RV2 can continue to be selected based on the lower voltage V1. Correspondingly, the operating voltage of the second gas discharge tube G2 can be selected based on the voltage difference (V2-V1). Since the voltage difference (V2-V1) is usually less than the aforementioned lower voltage V1, the voltage division ratio k4 of the second gas discharge tube G2 can be less than the voltage division ratio k3 of the second varistor RV2. Based on the above analysis, it can be seen that in photovoltaic inverters with higher operating voltages, since the specifications of the second varistor RV2 can continue to be the same as those in photovoltaic inverters with lower operating voltages, the complexity of varistor selection is effectively reduced.

[0067] In one possible implementation, the resistance value of the second voltage-dividing resistor R2 is greater than the resistance value of the first voltage-dividing resistor R1. Accordingly, the voltage division ratio k1 of the first varistor RV1 is greater than the voltage division ratio k2 of the first gas discharge tube G1.

[0068] In this embodiment, the specifications of the first varistor RV1 can continue to be the same as those in photovoltaic inverters with lower operating voltages; that is, the operating voltage of the first varistor RV1 can continue to be selected based on the lower voltage V1. Correspondingly, the operating voltage of the first gas discharge tube G1 can be selected based on the voltage difference (V2-V1). Since the voltage difference (V2-V1) is usually less than the aforementioned lower voltage V1, the voltage division ratio k2 of the first gas discharge tube G1 can be less than the voltage division ratio k1 of the first varistor RV1. Based on the above analysis, it can be seen that in photovoltaic inverters with higher operating voltages, since the specifications of the first varistor RV1 can continue to be the same as those in photovoltaic inverters with lower operating voltages, the complexity of varistor selection is effectively reduced.

[0069] In one possible implementation, such as Figure 4 As shown, the photovoltaic inverter also includes a DC-side surge protection device 30, which comprises multiple third surge protection units 31 and fourth surge protection units 32. For example, Figure 4 The diagram shows two third surge protection units 31 and one fourth surge protection unit 32. The first terminals of the multiple third surge protection units 31 are connected to the positive (PV+) and negative (PV-) terminals of the DC power supply, respectively, and the second terminals of the multiple third surge protection units 31 are connected to the second node N2. Specifically, the connection of the first terminals of the multiple third surge protection units 31 to the positive (PV+) and negative (PV-) terminals of the DC power supply can mean that at least one third surge protection unit 31 is connected to the positive (PV+) terminal of the DC power supply, and at least one third surge protection unit 31 is connected to the negative (PV-) terminal of the DC power supply.

[0070] Furthermore, refer to Figure 4 and Figure 5 The structure of the third surge protection unit 31 is the same as that of the first surge protection unit 21. That is, each third surge protection unit 31 includes: a first varistor RV1 and a first gas discharge tube G1 connected in series, and a first voltage divider resistor R1 connected in parallel with the first gas discharge tube G1. Alternatively, as... Figure 6 As shown, each third lightning protection unit 31 also includes a second voltage divider resistor R2 connected in parallel with the first varistor RV1.

[0071] Continue to refer to Figure 4 and Figure 5 The first end of the fourth lightning protection unit 32 is connected to the second node N2, and the second end of the fourth lightning protection unit 32 is used for grounding. Furthermore, the structure of this fourth lightning protection unit 32 is the same as that of the second lightning protection unit 22. That is, as... Figure 5 As shown, the second surge protection unit 22 includes a second varistor RV2. Alternatively, as... Figure 6As shown, the second lightning protection unit 22 includes: a second varistor RV2 connected in series and a second gas discharge tube G2, a third voltage divider resistor R3 connected in parallel with the second varistor RV2, and a fourth voltage divider resistor R4 connected in parallel with the second gas discharge tube G2.

[0072] refer to Figures 4 to 6 It can be seen that two third surge protection units 31 are connected in series between the positive terminal PV+ and the negative terminal PV- of the DC terminal of the power conversion circuit 10. That is, two third surge protection units 31 are connected in series in the differential mode circuit of the DC terminal of the power conversion circuit 10. These two third surge protection units 31 need to withstand the differential mode voltage of the DC terminal of the power conversion circuit 10 during normal operation to avoid malfunction of the surge protection units during normal operation of the power conversion circuit 10. For example, the two third surge protection units 31 need to withstand the string voltage of the photovoltaic string connected to the DC terminal, that is, the sum of the operating voltages of the two third surge protection units 31 needs to be greater than the string voltage U of the photovoltaic string. dc Since the two third surge protection units 31 have the same structure, the operating voltage of each third surge protection unit 31 must be greater than the string voltage U. dc 1 / 2, that is, greater than U dc / 2. Accordingly, when selecting the first varistor RV1 in the third lightning protection unit 31, it is necessary to ensure that its operating voltage is greater than k1×U. dc / 2, When selecting the first gas discharge tube G1 in the third lightning protection unit 31, it is necessary to ensure that its operating voltage is greater than k2×U. dc / 2.

[0073] refer to Figures 4 to 6 It can also be seen that a third surge protection unit 31 and a fourth surge protection unit 32 are connected in series between the positive terminal PV+ and ground, and between the negative terminal PV- and ground, respectively. That is, a third surge protection unit 31 and a fourth surge protection unit 32 are connected in series in the common-mode circuit of the DC terminal of the power conversion circuit 10. These three surge protection units 31 and 32 must also withstand the common-mode voltage of the DC terminal during normal operation of the power conversion circuit 10 to prevent malfunction of the surge protection units during normal operation. For example, the sum of the operating voltages of the three surge protection units 31 and 32 connected in series between the positive terminal PV+ and ground must be greater than the voltage of the positive terminal PV+ to ground. Similarly, the sum of the operating voltages of the three surge protection units 31 and 32 connected in series between the negative terminal PV- and ground must be greater than the voltage of the negative terminal PV- to ground. Since the third surge protection unit 31 and the fourth surge protection unit 32 can have the same structure, the operating voltage of each surge protection unit must be greater than the ground voltage U of the positive terminal PV+ / negative terminal PV-. pvHalf of that. Correspondingly, when selecting the first varistor RV1 on the DC side, it is also necessary to ensure that its operating voltage is greater than k1×U. pv / 2, When selecting the first gas discharge tube G1, it is also necessary to ensure that its operating voltage is greater than k2×U. pv / 2. When selecting the second varistor RV2, it is also necessary to ensure that its operating voltage is greater than k3×U. pv / 2, When selecting the second gas discharge tube G2, it is also necessary to ensure that its operating voltage is greater than k4×U pv / 2.

[0074] Based on the above analysis, it can be seen that the surge protection unit on the DC side of the photovoltaic inverter is also formed by connecting a gas discharge tube and a varistor in series. This effectively increases the operating voltage of the DC-side surge protection unit without increasing the operating voltage of the varistor or the residual voltage of the DC-side surge protection unit. Therefore, it ensures that the DC-side surge protection unit is compatible with photovoltaic inverters operating at higher voltages. Furthermore, because the voltage division ratio of the gas discharge tube and varistor can be flexibly adjusted by flexibly designing the resistance values ​​of the two voltage divider resistors in the surge protection unit, the selection flexibility of the gas discharge tube and varistor is effectively improved. Thus, even photovoltaic inverters operating at higher voltages can use gas discharge tubes and varistors with lower operating voltages and lower costs to form the surge protection unit.

[0075] In this embodiment of the application, the resistance values ​​of the second voltage divider resistor R2 to the fourth voltage divider resistor R4 in the DC side surge protection device 30 are all greater than or equal to 1MΩ, so as to ensure that the current flowing through the voltage divider resistor is small and will not affect the normal operation of the power conversion circuit 10.

[0076] Furthermore, in the DC-side surge protection device 30, the resistance value of the second voltage-dividing resistor R2 is greater than that of the first voltage-dividing resistor R1, and the resistance value of the third voltage-dividing resistor R3 is greater than that of the fourth voltage-dividing resistor R4. Correspondingly, in the DC-side surge protection device 30, the voltage division ratio of the first varistor RV1 is greater than that of the first gas discharge tube G1, and the voltage division ratio of the second varistor RV2 is greater than that of the second gas discharge tube G2. Therefore, it can be ensured that even in photovoltaic inverters with higher operating voltages, the varistor in the DC-side surge protection device 30 can continue to use the specifications found in photovoltaic inverters with lower operating voltages, thereby reducing the complexity of selecting the varistor in the DC-side surge protection device 30.

[0077] In one possible implementation, such as Figures 3 to 7 As shown, the power conversion circuit 10 includes a DC / DC conversion circuit 11 and a DC / AC conversion circuit 12. The DC / DC conversion circuit 11 is connected to the DC / AC conversion circuit 12 via a DC bus. For example, refer to... Figure 6The power conversion circuit 10 may include multiple DC / DC conversion circuits 11, which are connected in parallel to the DC bus. The DC / DC conversion circuits 11 are used to perform voltage conversion (e.g., boost) on the DC power supplied by the photovoltaic modules before outputting it to the subsequent DC / AC conversion circuit 12. The DC / AC conversion circuit 12 is used to convert the DC power output from the DC / DC conversion circuit 10 into AC power before outputting it to the grid or load. In scenarios where the photovoltaic inverter is an energy storage converter, the DC / AC conversion circuit 12 is also used to convert the AC power from the grid into DC power, and the DC / DC conversion circuits 11 are also used to perform voltage conversion on the DC power output from the DC / AC conversion circuit 12 to charge the energy storage battery.

[0078] In this embodiment, the DC terminal of the power conversion circuit 10 may include multiple pairs of photovoltaic (PV) terminals, each pair of PV terminals including a positive terminal and a negative terminal. For example, refer to... Figure 7 The DC terminal of the power conversion circuit 10 may include n pairs of PV terminals, where n is an integer greater than 1. Furthermore, from... Figure 7 As can be seen, each DC / DC converter circuit 11 in the power conversion circuit 10 can be connected to one or more PV terminals. For example, Figure 7 The first DC / DC converter circuit 11 in the circuit is connected to two pairs of PV terminals: (PV1+, PV1-) and (PV2+, PV2-).

[0079] For scenarios where the DC terminal of the power conversion circuit 10 includes multiple pairs of PV terminals, such as... Figure 7 As shown, the positive terminals of multiple pairs of PV terminals can be connected to the same third surge protection unit 31, and the negative terminal of one of the multiple pairs of PV terminals is connected to one third surge protection unit 31, while the negative terminals of other PV terminals are not directly connected to the third surge protection unit 31. For example, Figure 7 In the photovoltaic inverter, the negative terminal PVn- of the nth PV terminal pair is connected to the third surge protection unit 31, while the other negative terminals (e.g., PV1- to PV4-) are not connected to the third surge protection unit 31. In the photovoltaic inverter, the negative terminals of multiple PV terminals are connected one-to-one with one end of multiple switches, and the other ends of the multiple switches are interconnected and connected to the negative terminal of the DC / DC conversion circuit 11. When multiple switches are turned on, the negative terminals of multiple PV terminals are connected, meaning that the negative terminals of multiple PV terminals can share one third surge protection unit 31. Since the positive terminals of multiple PV terminals can share one third surge protection unit 31, and the negative terminals of multiple PV terminals can also share one third surge protection unit 31, this effectively avoids increasing the structural complexity and hardware cost of the photovoltaic inverter.

[0080] Of course, in the embodiments of this application, multiple pairs of PV terminals may not share the third surge protection unit 31. For example, the positive terminal of each pair of PV terminals may be connected to a third surge protection unit 31, and / or the negative terminal of each pair of PV terminals may be connected to a third surge protection unit 31.

[0081] In one possible implementation, the number of fourth surge protection units 32 included in the photovoltaic inverter is greater than the number of second surge protection units 22. For example, refer to... Figure 4 , Figure 6 and Figure 7 The photovoltaic inverter may include two fourth surge protection units 32 and one second surge protection unit 22. Each fourth surge protection unit 32 has its first end connected to the second node N2 and its second end used for grounding. Therefore, it can also be understood that these multiple fourth surge protection units 32 are connected in parallel between the second node N2 and the ground wire.

[0082] Because a large number of photovoltaic (PV) modules are connected to the DC terminal of a PV inverter, the area of ​​the induction loop formed by these modules (e.g., connected in series) is relatively large, resulting in a larger lightning strike energy at the DC terminal of the PV inverter. Therefore, the lightning protection test magnitude for the DC-side surge protection device 30 is typically greater than that for the AC-side surge protection device 20. Accordingly, the number of fourth surge protection units 32 in the DC-side surge protection device 30 is greater than the number of second surge protection units 22 in the AC-side surge protection device 20. This ensures that the multiple fourth surge protection units 32 in the DC-side surge protection device 30 effectively share the lightning strike energy, thereby ensuring higher lightning protection reliability of the DC-side surge protection device 30.

[0083] In one possible implementation, such as Figure 8 As shown, the photovoltaic inverter provided in this embodiment also includes a DC bus surge protection device 40, which includes multiple fifth surge protection units 41 and sixth surge protection units 42. The first ends of the multiple fifth surge protection units 41 are connected to the positive bus BUS+ and the negative bus BUS- of the DC bus, and the second ends of the multiple fifth surge protection units 41 are connected to the third node N3. For example, the photovoltaic inverter includes two fifth surge protection units 41, one of which has its first end connected to the positive bus BUS+, and the other has its first end connected to the negative bus BUS-. Furthermore, the structure of each fifth surge protection unit 41 is the same as that of the first surge protection unit 21. That is, as... Figure 8 As shown, each fifth lightning protection unit 41 includes: a first varistor RV1 and a first gas discharge tube G1 connected in series, a second voltage divider resistor R2 connected in parallel with the first varistor RV1, and a first voltage divider resistor R1 connected in parallel with the first gas discharge tube G1.

[0084] Continue to refer to Figure 8 The first end of the sixth surge protection unit 42 is connected to the third node N3, and the second end of the sixth surge protection unit 42 is used for grounding. Furthermore, the structure of the sixth surge protection unit 42 is the same as that of the second surge protection unit 22. That is, the sixth surge protection unit 42 includes a second varistor RV2. Alternatively, the sixth surge protection unit 42 includes: a second varistor RV2 and a second gas discharge tube G2 connected in series, a third voltage divider resistor R3 connected in parallel with the second varistor RV2, and a fourth voltage divider resistor R4 connected in parallel with the second gas discharge tube G2.

[0085] In this embodiment, the photovoltaic inverter may include one or more sixth lightning protection units 42. For example, refer to... Figure 8 The photovoltaic inverter includes two sixth lightning protection units 42.

[0086] The photovoltaic inverter provided in this application embodiment can achieve lightning protection for the DC bus by connecting a DC bus surge protection device to the DC bus. Furthermore, the structure of the surge protection unit in this DC bus surge protection device is the same as that in the AC side surge protection device. On the one hand, it can effectively increase the operating voltage of the surge protection unit without increasing the operating voltage of the varistor or the residual voltage of the surge protection unit, ensuring that the surge protection unit is compatible with photovoltaic inverters with higher operating voltages. On the other hand, by flexibly designing the resistance values ​​of each voltage divider resistor in the surge protection unit, the voltage division ratio of the gas discharge tube and the varistor can be flexibly adjusted, thereby effectively improving the selection flexibility of the gas discharge tube and the varistor.

[0087] The above description uses the example of one varistor and one gas discharge tube in each surge protection unit. Of course, each surge protection unit may also include multiple varistors connected in series, and / or multiple gas discharge tubes connected in series. This application does not limit the number of varistors and gas discharge tubes in the surge protection unit; it only needs to ensure that the surge protection unit's withstand voltage rating meets the operating voltage requirements of the photovoltaic inverter.

[0088] In summary, this application provides a power converter whose surge protection unit includes a varistor and a gas discharge tube connected in series. Because the gas discharge tube has low cost and high withstand voltage, the operating voltage of the surge protection unit can be effectively increased without increasing the operating voltage of the varistor, thus ensuring that the surge protection unit is suitable for high-voltage power converters. Furthermore, by connecting a voltage divider resistor in parallel to the gas discharge tube, flexible voltage division between the varistor and the gas discharge tube can be achieved, effectively improving the selection flexibility of the varistor and gas discharge tube, thereby ensuring that the cost of the varistor and gas discharge tube remains low. In addition, in lightning strike scenarios, because the voltage across the gas discharge tube is low (e.g., approximately 0) after activation, the series connection of the gas discharge tube does not increase the residual voltage of the surge protection unit, thus not increasing the protection performance requirements of the power devices in the power converter, ensuring that even power converters with high operating voltages can maintain low costs.

[0089] This application also provides another type of power converter, which can be a photovoltaic inverter or an energy storage converter, etc. The following description uses a photovoltaic inverter as an example; however, the embodiments of this application are equally applicable when the power converter is an energy storage converter, and will not be elaborated upon here. Figure 9 As shown, the photovoltaic inverter includes a power conversion circuit 10 and a DC-side surge protection device 30. The DC-side surge protection device 30 includes multiple third surge protection units 31 and fourth surge protection units 32. The DC terminal of the power conversion circuit 10 is used to connect to the photovoltaic module or energy storage battery, and the AC terminal is used to connect to the power grid or load. The power conversion circuit 10 converts the DC power from the photovoltaic module or energy storage battery into AC power for output. The first terminals of the multiple third surge protection units 31 are connected to the positive and negative terminals of the DC terminal, respectively, and the second terminals of the multiple third surge protection units 31 are connected to the second node N2. Furthermore, as... Figure 5 and Figure 6 As shown, the third surge protection unit 31 includes: a first varistor RV1 and a first gas discharge tube G1 connected in series, and a first voltage divider resistor R1 connected in parallel with the first gas discharge tube G1. The first end of the fourth surge protection unit 32 is connected to the second node N2, and the second end of the fourth surge protection unit 32 is used for grounding. Furthermore, the fourth surge protection unit 32 includes a second varistor RV2.

[0090] In one possible implementation, the third lightning protection unit 31 further includes a second voltage divider resistor R2 connected in parallel with the first varistor RV1.

[0091] In one possible implementation, the resistance value of the second voltage divider resistor R2 is greater than the resistance value of the first voltage divider resistor R1.

[0092] In one possible implementation, such as Figure 6As shown, the fourth lightning protection unit 32 also includes: a second gas discharge tube G2 connected in series with the second varistor RV2, a third voltage divider resistor R3 connected in parallel with the second varistor RV2, and a fourth voltage divider resistor R4 connected in parallel with the second gas discharge tube G2.

[0093] In one possible implementation, the resistance value of the third voltage divider resistor R3 is greater than the resistance value of the fourth voltage divider resistor R4.

[0094] In one possible implementation, the resistance value of the third voltage divider resistor R3 is greater than the resistance value of the fourth voltage divider resistor R4.

[0095] In one possible implementation, the resistance values ​​of the first voltage divider resistor R1, the second voltage divider resistor R2, the third voltage divider resistor R3, and the fourth voltage divider resistor R4 can all be greater than or equal to 1MΩ.

[0096] Figure 9 The structure, principle and technical effect of the third lightning protection unit 31 and the fourth lightning protection unit 32 in the photovoltaic inverter shown can be referred to the relevant descriptions in the foregoing embodiments, and will not be repeated here.

[0097] The above description uses the application of a power converter in a three-phase power system as an example. Of course, the power converter provided in this application embodiment can also be applied to a single-phase power system, i.e., the AC terminal of the power converter includes one phase line and one neutral line. Correspondingly, the AC side lightning protection device 20 of the power converter may include two first lightning protection units 21 connected one-to-one with the one phase line and the neutral line.

[0098] In the embodiments of this application, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "at least one" refers to one or more, and "multiple" refers to two or more.

[0099] In the embodiments of this application, the term "and / or" 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. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0100] The above description is merely an optional implementation of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered 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 power converter, characterized by, The power converter comprises a power conversion circuit, a plurality of first lightning protection units and a second lightning protection unit, wherein The direct current end of the power conversion circuit is used for connecting a photovoltaic module or an energy storage battery, and the alternating current end is used for connecting a power grid or a load, and the power conversion circuit is used for converting direct current of the photovoltaic module or the energy storage battery into alternating current and then outputting. The first ends of the plurality of first lightning protection units are connected to three phase lines of the alternating current end one by one, and the second ends of the plurality of first lightning protection units are connected to a first node, and the first lightning protection unit comprises a first voltage-dependent resistor and a first gas discharge tube connected in series, and a first voltage dividing resistor connected in parallel with the first gas discharge tube. The first end of the second lightning protection unit is connected to the first node, and the second end of the second lightning protection unit is used for grounding, and the second lightning protection unit comprises a second voltage-dependent resistor. The first lightning protection unit further comprises a second voltage dividing resistor connected in parallel with the first voltage-dependent resistor.

2. The power converter of claim 1, wherein, The resistance value of the second voltage dividing resistor is greater than that of the first voltage dividing resistor.

3. The power converter of claim 2, wherein, The second lightning protection unit further comprises a second gas discharge tube connected in series with the second voltage-dependent resistor, a third voltage dividing resistor connected in parallel with the second voltage-dependent resistor, and a fourth voltage dividing resistor connected in parallel with the second gas discharge tube.

4. The power converter of any one of claims 1 to 3, wherein, The resistance value of the third voltage dividing resistor is greater than that of the fourth voltage dividing resistor.

5. The power converter of claim 4, wherein, The power converter further comprises a plurality of third lightning protection units and a fourth lightning protection unit.

6. The power converter of any one of claims 1 to 5, wherein, The first ends of the plurality of third lightning protection units are connected to the positive and negative poles of the direct current end, and the second ends of the plurality of third lightning protection units are connected to a second node, and the third lightning protection unit has the same structure as the first lightning protection unit. The first end of the fourth lightning protection unit is connected to the second node, and the second end of the fourth lightning protection unit is used for grounding, and the fourth lightning protection unit has the same structure as the second lightning protection unit. The number of the fourth lightning protection units included in the power converter is greater than that of the second lightning protection units.

7. The power converter of claim 6, wherein, The power conversion circuit comprises a direct current / direct current (DC / DC) conversion circuit and a direct current / alternating current (DC / AC) conversion circuit, and the power converter further comprises a plurality of fifth lightning protection units and a sixth lightning protection unit, wherein 8. The power converter of any one of claims 1 to 7, wherein, The DC / DC conversion circuit is connected to the DC / AC conversion circuit through the direct current bus; The first ends of the plurality of fifth lightning protection units are connected to the positive bus and the negative bus of the direct current bus, and the second ends of the plurality of fifth lightning protection units are connected to a third node, and the fifth lightning protection unit has the same structure as the first lightning protection unit. The first end of the sixth lightning protection unit is connected to the third node, and the second end of the sixth lightning protection unit is used for grounding, and the sixth lightning protection unit has the same structure as the second lightning protection unit. The resistance values of the first voltage dividing resistor, the second voltage dividing resistor, the third voltage dividing resistor and the fourth voltage dividing resistor in the power converter are all greater than or equal to 1 megaohm.

9. The power converter of any of claims 1 to 8, wherein, The power converter comprises a power conversion circuit, a plurality of third lightning protection units and a fourth lightning protection unit, wherein 10. A power converter, characterized by, ​ ​ The direct current end of the power conversion circuit is used for connecting a photovoltaic module or an energy storage battery, and the alternating current end is used for connecting a power grid or a load. The first ends of the plurality of third lightning protection units are connected to the positive and negative poles of the direct current end, and the second ends of the plurality of third lightning protection units are connected to the second node, wherein the third lightning protection unit comprises a first voltage-dependent resistor and a first gas discharge tube connected in series, and a first voltage dividing resistor connected in parallel to the first gas discharge tube. The first end of the fourth lightning protection unit is connected to the second node, and the second end of the fourth lightning protection unit is used for grounding, wherein the fourth lightning protection unit comprises a second voltage-dependent resistor.

11. The power converter of claim 10, wherein, The third lightning protection unit further comprises a second voltage dividing resistor connected in parallel to the first voltage-dependent resistor.

12. The power converter of claim 11, wherein, The resistance value of the second voltage dividing resistor is greater than the resistance value of the first voltage dividing resistor.

13. A power converter as claimed in any one of claims 10 to 12, wherein, The fourth lightning protection unit further comprises a second gas discharge tube connected in series to the second voltage-dependent resistor, a third voltage dividing resistor connected in parallel to the second voltage-dependent resistor, and a fourth voltage dividing resistor connected in parallel to the second gas discharge tube.

14. The power converter of claim 13, wherein, The resistance value of the third voltage dividing resistor is greater than the resistance value of the fourth voltage dividing resistor.

15. A power converter as claimed in any one of claims 10 to 14, characterised in that, The resistance values of the first voltage dividing resistor, the second voltage dividing resistor, the third voltage dividing resistor and the fourth voltage dividing resistor in the power converter are all greater than or equal to 1 megaohm.

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