Voltage-sharing circuit and current converter

Abstract

The utility model provides a voltage-sharing circuit and a converter, the voltage-sharing circuit is applied to a converter valve, the converter valve comprises a first power semiconductor device and a second power semiconductor device which are connected in series, and the voltage-sharing circuit comprises a first voltage-sharing unit and a second voltage-sharing unit which are used for carrying out voltage sharing on the converter valve, the first end of the first voltage-sharing unit is used for being electrically connected with the first end of a first power semiconductor device, and the second end of the first voltage-sharing unit and the first end of the second voltage-sharing unit are respectively used for being electrically connected with the second end of the first power semiconductor device. And the fourth end of the second voltage-sharing unit is electrically connected with the second end of the second power semiconductor device. According to the voltage-sharing circuit, the voltage balance degree between adjacent semiconductor devices during steady-state operation can be improved, and meanwhile, the overvoltage degree during active turn-off of the devices and the imbalance degree between the devices can be reduced; therefore, the problem of voltage imbalance caused by inconsistency of dispersity or trigger signals of the power semiconductor devices in the prior art is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of circuit, in particular to a voltage equalization circuit and a converter. BACKGROUND

[0002] In the field of power electronics, especially in high-voltage direct current transmission systems, converter valves are indispensable key components for realizing efficient conversion between high-voltage direct current and alternating current.

[0003] However, in current converter valve designs, especially in high-voltage direct current transmission systems, a more advanced voltage equalization circuit is needed that can effectively handle voltage equalization during the reverse recovery phase of the devices, significantly reduce the overvoltage effect during active turn-off, and have higher reliability and lower loss to adapt to the development trend of high-power and high-efficiency power electronic systems. CONTENT OF THE INVENTION

[0004] The main purpose of the present application is to provide a voltage equalization circuit and a converter to at least solve the problem of voltage imbalance between series-connected power semiconductor devices in the related art.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a voltage equalization circuit is provided, which is applied to a converter valve, the converter valve comprising a first power semiconductor device and a second power semiconductor device connected in series, a second end of the first power semiconductor device being electrically connected with a first end of the second power semiconductor device, wherein the voltage equalization circuit comprises: a first voltage equalization unit and a second voltage equalization unit for voltage equalization of the converter valve, a first end of the first voltage equalization unit being used for electrical connection with a first end of the first power semiconductor device, a second end of the first voltage equalization unit and a first end of the second voltage equalization unit being respectively used for electrical connection with a second end of the first power semiconductor device, a third end of the first voltage equalization unit being electrically connected with a second end of the second voltage equalization unit, a fourth end of the first voltage equalization unit being electrically connected with a third end of the second voltage equalization unit, and a fourth end of the second voltage equalization unit being used for electrical connection with a second end of the second power semiconductor device.

[0006] Optionally, the first voltage equalization unit comprises a first impedance, a second impedance and a first switching device, wherein a first end of the first impedance is electrically connected with a first end of the second impedance and is the first end of the first voltage equalization unit, a second end of the first impedance is the third end of the first voltage equalization unit, a second end of the second impedance is electrically connected with a first end of the first switching device and is the fourth end of the first voltage equalization unit, and a second end of the first switching device is the second end of the first voltage equalization unit.

[0007] Optionally, the first impedance is a resistor, the second impedance is a capacitor, the first switch device is a diode, a first end of the second impedance is a positive electrode of the capacitor, a second end of the second impedance is a negative electrode of the capacitor, a first end of the first switch device is a positive electrode of the diode, and a second end of the first switch device is a negative electrode of the diode.

[0008] Optionally, the second voltage equalization unit comprises a third impedance, a fourth impedance, and a second switch device, wherein a first end of the second switch device is a first end of the second voltage equalization unit, a first end of the third impedance is a third end of the second voltage equalization unit, a second end of the second switch device is electrically connected with a first end of the fourth impedance and is a second end of the second voltage equalization unit, and a second end of the fourth impedance is electrically connected with a second end of the third impedance and is a fourth end of the second voltage equalization unit.

[0009] Optionally, the third impedance is a resistor, the fourth impedance is a capacitor, the second switch device is a diode, a first end of the fourth impedance is a positive electrode of the capacitor, a second end of the fourth impedance is a negative electrode of the capacitor, a first end of the second switch device is a positive electrode of the diode, and a second end of the second switch device is a negative electrode of the diode.

[0010] Optionally, the voltage equalization circuit further comprises a third voltage equalization unit and a fourth voltage equalization unit, wherein the third voltage equalization unit and the fourth voltage equalization unit are configured to equalize voltage of the converter valve, a first end of the third voltage equalization unit is electrically connected with a first end of the first voltage equalization unit, a second end of the third voltage equalization unit is electrically connected with a fourth end of the first voltage equalization unit, a first end of the fourth voltage equalization unit is electrically connected with a second end of the second voltage equalization unit, and a second end of the fourth voltage equalization unit is electrically connected with a fourth end of the second voltage equalization unit.

[0011] Optionally, the third voltage equalization unit comprises a third switch device and a fifth impedance, wherein a first end of the third switch device is a first end of the third voltage equalization unit, a second end of the third switch device is electrically connected with a first end of the fifth impedance, and a second end of the fifth impedance is a fourth end of the first voltage equalization unit.

[0012] Optionally, the third switch device is a diode or a reverse conducting device, and the fifth impedance is a capacitor.

[0013] Optionally, the fourth voltage equalization unit comprises a fourth switch device and a sixth impedance, wherein a first end of the fourth switch device is a first end of the fourth voltage equalization unit, a second end of the fourth switch device is electrically connected with a first end of the sixth impedance, and a second end of the sixth impedance is a second end of the fourth voltage equalization unit.

[0014] Optionally, the fourth switching device is an anti-parallel diode of a fully controlled device or a reverse conducting device, and the sixth impedance is a capacitor.

[0015] According to another aspect of the present application, a converter is provided, comprising a converter valve and any one of the voltage equalization circuits, the voltage equalization circuit being configured to equalize voltage of the converter valve.

[0016] By applying the technical solution of the present application, a voltage equalization circuit is provided. In the case that the voltage of the series-connected power semiconductor devices is zero, the internal residual carriers need time to recombine, forming a reverse recovery current. In the reverse recovery process, the first voltage equalization unit and the second voltage equalization unit are connected in the manner as provided in the present solution, the first voltage equalization unit, the second voltage equalization unit and the series-connected power semiconductor devices form a parallel structure, and the reverse recovery voltage equalization effect is better than that of the single-branch series structure in the prior art. At the same time, the circuit structure in the present solution does not additionally increase components and devices, has good economy, and can reduce the overvoltage degree in the reverse recovery process of the devices and the imbalance degree between the devices while improving the voltage balance degree between the adjacent semiconductor devices in the steady state, thereby solving the problem of voltage imbalance caused by the dispersion of the power semiconductor devices or the inconsistency of the trigger signals in the related art. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings constituting a part of the present application are used to provide further understanding of the present application, the illustrative embodiments of the present application and the description thereof are used to explain the present application, and do not constitute improper limitation to the present application. In the drawings:

[0018] Figure 1 A circuit diagram of a voltage equalization circuit in the related art is shown;

[0019] Figure 2 A circuit diagram of a first voltage equalization circuit provided in an embodiment of the present application is shown;

[0020] Figure 3 A circuit diagram of a second voltage equalization circuit provided in an embodiment of the present application is shown;

[0021] Figure 4 A working schematic diagram of the second voltage equalization circuit in the turn-off process is shown in an embodiment of the present application;

[0022] Figure 5 A working schematic diagram of the second voltage equalization circuit in the turn-on process is shown in an embodiment of the present application;

[0023] Figure 6 A circuit diagram of a third voltage equalization circuit provided in an embodiment of the present application is shown;

[0024] Figure 7 a circuit diagram of a fourth voltage-sharing circuit provided in the embodiments of the present application is shown;

[0025] Figure 8 a working schematic diagram of the fourth voltage-sharing circuit in a process of active turn-off is shown;

[0026] Figure 9 a working schematic diagram of the fourth voltage-sharing circuit in a process of turn-on is shown.

[0027] In the above drawings, the following reference signs are used:

[0028] 1, converter valve; 11, first power semiconductor device; 12, second power semiconductor device; 2, first voltage-sharing unit; 3, second voltage-sharing unit; 21, first impedance; 22, second impedance; 23, first switching device; 31, third impedance; 32, second switching device; 33, fourth impedance; 4, fourth voltage-sharing unit; 41, sixth impedance; 42, fourth switching device; 5, third voltage-sharing unit; 51, fifth impedance; 52, third switching device. DETAILED DESCRIPTION

[0029] It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict. The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0030] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0031] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented. In addition, the terms "comprise" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device comprising a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0032] As Figure 1As shown, the conventional converter valve design relies on a large-scale series connection of high-voltage high-power devices, such as IGCT, to form the core through-flow and blocking path. However, such a series connection structure may have problems in the case of device reverse recovery and active turn-off. When the device is in reverse recovery, the converter valve based on high-voltage high-power devices usually adopts an RC damping circuit for voltage equalization. Although such a passive voltage equalization circuit has a simple structure and high reliability, the voltage equalization effect is limited in the transient change process. This is because the traditional RC or RCD circuit only acts on a single device, although it can slow down the voltage change rate, it is difficult to effectively balance the voltage fluctuation between adjacent devices in more complex working conditions. With the development of semiconductor technology, the improvement of device power level and the diversification of operating environment, such single-device-level voltage equalization strategy gradually exposes its limitations, especially during device reverse recovery, which may lead to uneven voltage distribution, thereby threatening the operation stability of the device and the safety of the entire converter valve. In the active turn-off state, the traditional converter valve design uses a lightning arrester to suppress overvoltage. The lightning arrester has low reliability and the internal fuse and lightning arrester energy coordination are complex, which has potential risks. During normal operation of the converter valve, the lightning arrester is always connected to the voltage equalization circuit, which not only increases the complexity and construction cost of the system, but also in the case of failure, the explosion risk of the lightning arrester becomes an unavoidable safety hazard. In addition, the lightning arrester has limited effect on overvoltage suppression in the active turn-off process, and cannot effectively deal with the voltage imbalance problem caused by drive delay or device characteristic difference, thereby limiting the application and performance optimization of the converter valve in the field of high-voltage direct current transmission.

[0033] As introduced in the background, the voltage equalization effect of the voltage equalization circuit in the related art is not ideal, to solve the above problems, the embodiments of the present application provide a voltage equalization circuit and a converter.

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

[0035] Figure 2 , Figure 3 , Figure 6 and Figure 7 is a circuit diagram of a voltage equalization circuit according to an embodiment of the present application. As Figure 2 , Figure 3 , Figure 6 and Figure 7As shown, the voltage equalization circuit is applied to a converter valve 1, the converter valve 1 includes a first power semiconductor device 11 and a second power semiconductor device 12 connected in series, a second end of the first power semiconductor device 11 is electrically connected to a first end of the second power semiconductor device 12, and the voltage equalization circuit includes a first voltage equalization unit 2 and a second voltage equalization unit 3 for voltage equalization of the converter valve 1, a first end of the first voltage equalization unit 2 is configured to be electrically connected to a first end of the first power semiconductor device 11, a second end of the first voltage equalization unit 2 and a first end of the second voltage equalization unit 3 are configured to be electrically connected to a second end of the first power semiconductor device 11, a third end of the first voltage equalization unit 2 is electrically connected to a second end of the second voltage equalization unit 3, a fourth end of the first voltage equalization unit 2 is electrically connected to a third end of the second voltage equalization unit 3, and a fourth end of the second voltage equalization unit 3 is configured to be electrically connected to a second end of the second power semiconductor device 12.

[0036] The first power semiconductor device and the second power semiconductor device can be used as main current branches and blocking structures of the converter valve. In actual applications, the voltage equalization circuit can be further applied to a converter valve including N power semiconductor devices, where N is an even number, and the voltage equalization circuits of every two adjacent power semiconductor devices adopt the connection mode of the voltage equalization circuit. The first voltage equalization unit and the second voltage equalization unit can be passive voltage equalization circuits, for example, RC voltage equalization circuits, RCD voltage equalization circuits, and RLC voltage equalization circuits. The RC voltage equalization circuit is composed of a resistor and a capacitor connected in series or parallel, and the voltage is balanced by using the charge and discharge characteristics of the capacitor. The RCD voltage equalization circuit adds a diode to the RC circuit to prevent the capacitor voltage from reversing and improve the reliability of the voltage equalization circuit. The RLC voltage equalization circuit introduces an inductor element to form a resistor, a capacitor, and an inductor, which is used to suppress the voltage change rate and improve the voltage stability. The internal structures of the first voltage equalization unit and the second voltage equalization unit can be the same or different.

[0037] According to the embodiment, the voltage equalization circuit is provided. In the case that the voltage of the series-connected power semiconductor devices is zero, the internal residual carriers need time to recombine, forming a reverse recovery current. In the reverse recovery process, the first voltage equalization unit and the second voltage equalization unit are connected in the connection mode of the embodiment, the first voltage equalization unit, the second voltage equalization unit, and the series-connected power semiconductor devices form a parallel structure, and the reverse recovery voltage equalization effect is better than that of the single-branch series structure in the prior art. At the same time, the circuit structure in the embodiment does not increase additional components, has good economy, and can improve the voltage balance degree between adjacent semiconductor devices in the steady state and reduce the overvoltage degree during the reverse recovery of the device and the imbalance degree between devices, thereby solving the problem of voltage imbalance caused by the dispersion of power semiconductor devices or inconsistent trigger signals in the related art.

[0038] In the implementation process, as shown in Figure 3 The first equalizing unit 2 includes a first impedance 21, a second impedance 22, and a first switching device 23. The first end of the first impedance 21 is electrically connected to the first end of the second impedance 22 and is the first end of the first equalizing unit 2. The second end of the first impedance 21 is the third end of the first equalizing unit 2. The second end of the second impedance 22 is electrically connected to the first end of the first switching device 23 and is the fourth end of the first equalizing unit 2. The second end of the first switching device 23 is the second end of the first equalizing unit 2. The above connection mode can further improve the equalizing effect of the first equalizing unit 2.

[0039] To further simplify the first equalizing unit 2, as shown in Figure 3 The first impedance 21 is a resistor, the second impedance 22 is a capacitor, the first switching device 23 is a diode, the first end of the second impedance 22 is the positive electrode of the capacitor, the second end of the second impedance 22 is the negative electrode of the capacitor, the first end of the first switching device 23 is the positive electrode of the diode, and the second end of the first switching device 23 is the negative electrode of the diode.

[0040] In actual application, the resistance value of the first impedance can be set according to actual conditions, and the capacitance value of the second impedance can also be set according to actual conditions. In a specific embodiment, the capacitance value of the second impedance can be a small capacitance value. In this way, the capacitor can be charged and discharged faster, thereby providing a fast response capability when the voltage changes, achieving fast equalization, and preventing damage to the power semiconductor device caused by transient voltage spikes. In addition, the specific type of the diode can also be selected according to actual needs.

[0041] As shown in Figure 3 The second equalizing unit 3 includes a third impedance 31, a fourth impedance 33, and a second switching device 32. The first end of the second switching device 32 is the first end of the second equalizing unit 3. The first end of the third impedance 31 is the third end of the second equalizing unit 3. The second end of the second switching device 32 is electrically connected to the first end of the fourth impedance 33 and is the second end of the second equalizing unit 3. The second end of the fourth impedance 33 is electrically connected to the second end of the third impedance 31 and is the fourth end of the second equalizing unit 3. The above connection mode can further improve the equalizing effect of the second equalizing unit 3.

[0042] Specifically, as shown in Figure 3As shown, the second impedance 22, the first impedance 21, the fourth impedance 33 and the third impedance 31 form a loop, wherein the positive pole of the second impedance 22 is connected with the positive pole of the fourth impedance 33 via the first impedance 21, the negative pole of the second impedance 22 is connected with the negative pole of the fourth impedance 33 via the third impedance 31, and the second impedance 22 and the fourth impedance 33 are connected in parallel through the two resistors (i.e. the first impedance and the third impedance). When the voltage of the second impedance 22 and the fourth impedance 33 is not balanced, the discharge will be performed through the resistors (i.e. the first impedance and the third impedance) until the voltage of the capacitors (i.e. the second impedance 22 and the fourth impedance 33) is balanced. Figure 4 As shown, the second impedance 22 and the first switch device 23 form a snubber loop of the first power semiconductor device 11, and the fourth impedance 33 and the second switch device 32 form a snubber loop of the second power semiconductor device 12. When the voltage of the first power semiconductor device 11 and the second power semiconductor device 12 is not balanced due to inconsistent turn-on or other reasons, the voltage imbalance problem can be solved by balancing the voltage between the second impedance 22 and the fourth impedance 33 through the parallel loop. Figure 5 As shown, the fourth impedance 33 discharges through the first impedance 21, the first power semiconductor device 11 and the second power semiconductor device 12, and the second impedance 22 discharges through the third impedance 31, the first power semiconductor device 11 and the second power semiconductor device 12, without passing through the second switch device 32 and the first switch device 23.

[0043] In some embodiments, as shown, Figure 3 As shown, the third impedance 31 is a resistor, the fourth impedance 33 is a capacitor, the second switch device 32 is a diode, the first end of the fourth impedance 33 is the positive pole of the capacitor, the second end of the fourth impedance 33 is the negative pole of the capacitor, the first end of the second switch device 32 is the positive pole of the diode, and the second end of the second switch device 32 is the negative pole of the diode. The above device design can further simplify the second voltage balancing unit 3.

[0044] In practical applications, the resistance value of the third impedance can be set according to actual conditions, and the capacitance value of the fourth impedance can also be set according to actual conditions. In another specific embodiment, the capacitance value of the fourth impedance can be a small capacitance value, so that the capacitor can be charged and discharged faster, thereby providing a fast response capability when the voltage changes, achieving fast voltage balancing, and preventing damage to the power semiconductor device caused by transient voltage spikes. In addition, the specific type of diode can also be selected according to actual needs.

[0045] In order to further suppress the overvoltage caused by the active turn-off process, thereby achieving voltage balancing in the active turn-off process of the thyristor, as shown, Figure 6 and Figure 7As shown in the above embodiment, the voltage equalization circuit further includes: a third voltage equalization unit 5 and a fourth voltage equalization unit 4. The third voltage equalization unit 5 and the fourth voltage equalization unit 4 are used to equalize the voltage of the converter valve 1. The first end of the third voltage equalization unit 5 is electrically connected to the first end of the first voltage equalization unit 2, and the second end of the third voltage equalization unit 5 is electrically connected to the fourth end of the first voltage equalization unit 2. The first end of the fourth voltage equalization unit 4 is electrically connected to the second end of the second voltage equalization unit 3, and the second end of the fourth voltage equalization unit 4 is electrically connected to the fourth end of the second voltage equalization unit 3.

[0046] like Figure 7 As shown, the third voltage equalization unit 5 includes a third switching device 52 and a fifth impedance 51. The first terminal of the third switching device 52 is the first terminal of the third voltage equalization unit 5, and the second terminal of the third switching device 52 is electrically connected to the first terminal of the fifth impedance 51. The second terminal of the fifth impedance 51 is the fourth terminal of the first voltage equalization unit 2. This configuration can further enhance the voltage equalization effect of the third voltage equalization unit 5.

[0047] like Figure 8 and Figure 9 As shown, the third switching device 52 is a fully controlled anti-parallel diode or a reverse-conducting device, and the fifth impedance 51 is a capacitor. This device design can further simplify the third voltage equalization unit 5.

[0048] Specifically, the capacitance value of the fifth impedance can be set according to the actual situation. Using a fully controlled anti-parallel diode or a reverse-conducting device as the third switching device enhances the circuit's bidirectional operation capability, enabling the circuit to operate not only under forward voltage but also under reverse voltage for effective energy management and voltage equalization. Furthermore, fully controlled devices have lower turn-off losses and perform better in high-frequency switching operations compared to traditional semi-controlled devices, reducing unnecessary energy loss. Simultaneously, the anti-parallel diode or reverse-conducting device allows current to naturally freewheel when the device is turned off, avoiding additional energy consumption and further improving circuit efficiency.

[0049] like Figure 7 As shown, the fourth voltage equalization unit 4 includes a fourth switching device 42 and a sixth impedance 41. The first terminal of the fourth switching device 42 is the first terminal of the fourth voltage equalization unit 4, and the second terminal of the fourth switching device 42 is electrically connected to the first terminal of the sixth impedance 41. The second terminal of the sixth impedance 41 is the second terminal of the fourth voltage equalization unit 4. This configuration can further enhance the voltage equalization effect of the fourth voltage equalization unit 4.

[0050] like Figure 7As shown, when the series device is reversed, at this time, the switching device in the fourth voltage balancing unit 4 and the third voltage balancing unit 5 is in the off state and does not work, the first voltage balancing unit 2 and the second voltage balancing unit 3 work, the overall structure is a parallel structure, when the capacitor (i.e. the second impedance 22 and the fourth impedance 33) voltage is uneven, it will discharge through the resistor (i.e. the first impedance and the third impedance), until the capacitor (i.e. the second impedance 22 and the fourth impedance 33) voltage reaches balance. At the same time, the parallel structure of the first voltage balancing unit 2 and the second voltage balancing unit 3 can further increase the capacitance value, and the reverse recovery voltage balancing effect is better than that of the original single branch series structure.

[0051] The fourth switching device 42 is a full-controlled device anti-parallel diode or a reverse-conducting device, and the sixth impedance 41 is a capacitor. The above-mentioned device design can further simplify the fourth voltage balancing unit 4.

[0052] The capacitance value of the sixth impedance can be set according to actual conditions. The fourth switching device adopts a full-controlled device anti-parallel diode or a reverse-conducting device, which can enhance the bidirectional operation capability of the circuit, so that the circuit can not only work under forward voltage, but also can effectively manage energy and operate voltage balancing under reverse voltage. Moreover, compared with the voltage balancing topology of the traditional full-controlled device, the capacitor can perform better in high-frequency switching operation through charging and discharging, and at the same time, the active turn-off voltage balancing circuit is only put into use when it is turned off, thereby reducing unnecessary energy loss.

[0053] The active turn-off process of the converter valve is as shown in Figure 8 As shown, when the first power semiconductor device 11 and the second power semiconductor device 12 in series are actively turned off, the second impedance 22, the first switching device 23, the third switching device 52 and the fifth impedance 51 constitute a buffer circuit of the first power semiconductor device 11, and the fourth impedance 33, the second switching device 32, the fourth switching device 42 and the sixth impedance 41 constitute a buffer circuit of the second power semiconductor device 12. When an AC fault occurs in the DC system, the valve control issues an active turn-off signal, and the first power semiconductor device 11 and the second power semiconductor device 12 are inconsistent in turn-off due to inconsistent device parameters and other reasons. At this time, when the first power semiconductor device 11 and the second power semiconductor device 12 receive the turn-off signal, the third switching device 52 and the fourth switching device 42 generate an on signal by taking the non of the turn-off signal, and the first switching device 23, the second impedance 22, the third switching device 52 and the fifth impedance 51 form an active voltage balancing circuit of the first power semiconductor device 11 to suppress turn-off overvoltage; and the second switching device 32, the fourth impedance 33, the fourth switching device 42 and the sixth impedance 41 constitute an active voltage balancing circuit of the second power semiconductor device 12 to suppress turn-off overvoltage. The conduction process of the converter valve is as shown in Figure 9As shown, at this time, the fourth switching device 42 and the third switching device 52 (the antiparallel diode of which bears positive voltage) are turned on, and the sixth impedance 41 and the fourth impedance 33 are discharged through the first impedance 21, the first power semiconductor device 11, and the second power semiconductor device 12; the second impedance 22 and the fifth impedance 51 are discharged through the third impedance 31, the first power semiconductor device 11, and the second power semiconductor device 12.

[0054] In some embodiments, the voltage equalization circuit further comprises a seventh impedance, an eighth impedance, and a fifth switching device, wherein the seventh impedance is a resistor, the eighth impedance is a capacitor, and the fifth switching device is a diode; two ends of the seventh impedance are connected to the anode and the cathode of the power semiconductor device respectively, the cathode of the fifth switching device is connected to the anode of the power semiconductor device, and the anode of the fifth switching device is connected to one end of the eighth impedance; the other end of the eighth impedance is connected to the cathode of the power semiconductor device. The seventh impedance, the eighth impedance, and the fifth switching device form a passive voltage equalization circuit as a redundant voltage equalization branch of the voltage equalization circuit, so that the series power semiconductor device can further achieve voltage equalization without any control power supply, and the stability of the voltage equalization circuit is further improved at a lower cost.

[0055] In actual applications, the resistance value of the seventh impedance ranges from 100 kΩ to 1 MΩ, and the seventh impedance serves as a static voltage equalization resistor and is responsible for flattening the static leakage current. The eighth impedance and the fifth switching device form a series branch, the eighth impedance is only charged at the moment of turn-off, and forms a dynamic voltage divider; and the fifth switching device ensures that the eighth impedance is involved only during the reverse recovery period, and does not consume power at ordinary times.

[0056] In other embodiments, the voltage equalization circuit further comprises a ninth impedance and a tenth impedance, the ninth impedance and the tenth impedance are resistors, the ninth impedance is connected in series with the seventh impedance, the tenth impedance is connected in series with the eighth impedance and the fifth switching device, and the ninth impedance and the tenth impedance serve as an overload protection circuit of the voltage equalization circuit to prevent the voltage equalization branch (resistor, capacitor, and switching device) from being burned out due to overvoltage, overcurrent, and overtemperature, and to further balance the voltage of the entire string of devices at the moment of breakdown. Therefore, the ninth impedance and the tenth impedance can further protect the voltage equalization circuit.

[0057] In actual applications, the resistance value of the ninth impedance can range from 1 MΩ to 1.1 MΩ, and the resistance value of the tenth impedance can range from 2 Ω to 2.5 Ω.

[0058] The embodiments of the present application also provide a converter, which comprises a converter valve and any one of the voltage equalization circuits described above, and the voltage equalization circuit is used for voltage equalization of the converter valve.

[0059] Specifically, the present application does not limit the type of the converter, which can be a current source type converter or a voltage source type converter.

[0060] The technical features of the above-mentioned embodiments can be combined in any manner. For the sake of brevity, not all possible combinations of the technical features in the above-mentioned embodiments are described, but it should be understood that any combination of the technical features is within the scope of the present disclosure as long as the combination does not result in contradictions.

[0061] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects:

[0062] 1. The voltage equalization circuit of the embodiments of the present application, in the case of voltage zero of the series-connected power semiconductor devices, the internal residual carriers need to be recombined, forming a reverse recovery current, that is, during reverse recovery, the first voltage equalization unit and the second voltage equalization unit in the present solution are connected in parallel with the series-connected power semiconductor devices, which has better reverse recovery voltage equalization effect than the single-branch series structure in the prior art. At the same time, the circuit structure in the present solution does not increase additional components, has good economy, and can reduce the overvoltage degree during device reverse recovery and the imbalance degree between devices while improving the voltage balance degree between adjacent semiconductor devices during steady-state operation, thereby solving the problem of voltage imbalance caused by the dispersion of power semiconductor devices or inconsistent trigger signals in the related art.

[0063] 2. The converter of the embodiments of the present application, comprising a converter valve and a voltage equalization circuit, in the case of voltage zero of the series-connected power semiconductor devices, the internal residual carriers need to be recombined, forming a reverse recovery current, that is, during reverse recovery, the first voltage equalization unit and the second voltage equalization unit in the present solution are connected in parallel with the series-connected power semiconductor devices, which has better reverse recovery voltage equalization effect than the single-branch series structure in the prior art. At the same time, the circuit structure in the present solution does not increase additional components, has good economy, and can reduce the overvoltage degree during device reverse recovery and the imbalance degree between devices while improving the voltage balance degree between adjacent semiconductor devices during steady-state operation, thereby solving the problem of voltage imbalance caused by the dispersion of power semiconductor devices or inconsistent trigger signals in the related art.

[0064] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various changes and modifications to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A voltage equalization circuit, characterized in that, This is applied to a converter valve, which includes a first power semiconductor device and a second power semiconductor device connected in series. The second terminal of the first power semiconductor device is electrically connected to the first terminal of the second power semiconductor device. The voltage equalization circuit includes: a first voltage equalization unit and a second voltage equalization unit for equalizing the voltage of the converter valve. A first end of the first voltage equalization unit is electrically connected to a first end of the first power semiconductor device. A second end of the first voltage equalization unit and a first end of the second voltage equalization unit are respectively electrically connected to a second end of the first power semiconductor device. A third end of the first voltage equalization unit is electrically connected to a second end of the second voltage equalization unit. A fourth end of the first voltage equalization unit is electrically connected to a third end of the second voltage equalization unit. A fourth end of the second voltage equalization unit is electrically connected to a second end of the second power semiconductor device.

2. The voltage equalization circuit according to claim 1, characterized in that, The first voltage equalization unit includes a first impedance, a second impedance, and a first switching device. The first end of the first impedance is electrically connected to the first end of the second impedance and is the first end of the first voltage equalization unit. The second end of the first impedance is the third end of the first voltage equalization unit. The second end of the second impedance is electrically connected to the first end of the first switching device and is the fourth end of the first voltage equalization unit. The second end of the first switching device is the second end of the first voltage equalization unit.

3. The voltage equalization circuit according to claim 2, characterized in that, The first impedance is a resistor, the second impedance is a capacitor, the first switching device is a diode, the first end of the second impedance is the positive terminal of the capacitor, the second end of the second impedance is the negative terminal of the capacitor, the first end of the first switching device is the positive terminal of the diode, and the second end of the first switching device is the negative terminal of the diode.

4. The voltage equalization circuit according to claim 1, characterized in that, The second voltage equalization unit includes a third impedance, a fourth impedance, and a second switching device. The first terminal of the second switching device is the first terminal of the second voltage equalization unit, the first terminal of the third impedance is the third terminal of the second voltage equalization unit, the second terminal of the second switching device is electrically connected to the first terminal of the fourth impedance and is the second terminal of the second voltage equalization unit, and the second terminal of the fourth impedance is electrically connected to the second terminal of the third impedance and is the fourth terminal of the second voltage equalization unit.

5. The voltage equalization circuit according to claim 4, characterized in that, The third impedance is a resistor, the fourth impedance is a capacitor, the second switching device is a diode, the first end of the fourth impedance is the positive terminal of the capacitor, the second end of the fourth impedance is the negative terminal of the capacitor, the first end of the second switching device is the positive terminal of the diode, and the second end of the second switching device is the negative terminal of the diode.

6. The voltage equalization circuit according to claim 1, characterized in that, The voltage equalization circuit further includes a third voltage equalization unit and a fourth voltage equalization unit, which are used to equalize the pressure of the converter valve. The first end of the third voltage equalization unit is electrically connected to the first end of the first voltage equalization unit, the second end of the third voltage equalization unit is electrically connected to the fourth end of the first voltage equalization unit, the first end of the fourth voltage equalization unit is electrically connected to the second end of the second voltage equalization unit, and the second end of the fourth voltage equalization unit is electrically connected to the fourth end of the second voltage equalization unit.

7. The voltage equalization circuit according to claim 6, characterized in that, The third voltage equalization unit includes a third switching device and a fifth impedance, wherein the first end of the third switching device is the first end of the third voltage equalization unit, the second end of the third switching device is electrically connected to the first end of the fifth impedance, and the second end of the fifth impedance is the fourth end of the first voltage equalization unit.

8. The voltage equalization circuit according to claim 7, characterized in that, The third switching device is a fully controlled device, an anti-parallel diode, or a reverse-conducting device, and the fifth impedance is a capacitor.

9. The voltage equalization circuit according to claim 6, characterized in that, The fourth voltage equalization unit includes a fourth switching device and a sixth impedance, wherein the first end of the fourth switching device is the first end of the fourth voltage equalization unit, the second end of the fourth switching device is electrically connected to the first end of the sixth impedance, and the second end of the sixth impedance is the second end of the fourth voltage equalization unit.

10. The voltage equalization circuit according to claim 9, characterized in that, The fourth switching device is a fully controlled device, an anti-parallel diode, or a reverse-conducting device, and the sixth impedance is a capacitor.

11. A converter, characterized in that, include: The switching valve and the pressure equalization circuit according to any one of claims 1 to 10, wherein the pressure equalization circuit is used to equalize the pressure of the switching valve.

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