Current source converter, control method and system

Abstract

The application provides a current source converter, a control method and a system. The current source converter comprises a first bridge arm module and a second bridge arm module, the first bridge arm module comprises a plurality of first bridge arms, the second bridge arm module comprises a plurality of second bridge arms, each output end of a three-phase power supply is connected with one first bridge arm in the first bridge arm module and one second bridge arm in the second bridge arm module respectively, each first bridge arm comprises a plurality of first power devices respectively, and each second bridge arm comprises a plurality of second power devices respectively; at least one first auxiliary module is at least partially connected on the first bridge arm and electrically connected with the first poles of the first power devices to provide commutation voltage compensation for a faulty first bridge arm; and at least one second auxiliary module is at least partially connected on the second bridge arm and electrically connected with the first poles of the second power devices to provide commutation voltage compensation for a faulty second bridge arm, so that the problem of low commutation efficiency of the current source converter is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-voltage direct current transmission, in particular to a current source converter, a control method of the current source converter and a current source converter system. BACKGROUND

[0002] High-voltage direct current transmission is one of the key technical means for improving uneven load spatial distribution, large-scale clean energy transmission and reliable load supply. The current source converter is widely used in high-voltage direct current transmission, medium-high voltage traction and energy conversion due to its excellent output characteristics.

[0003] However, the high-voltage converter with high-voltage and high-power devices connected in series has difficulty in effectively controlling the current interruption, the voltage across the bridge or the voltage between devices during commutation, which easily leads to voltage and current fluctuations, affecting the stability and output quality of the system. Therefore, the commutation efficiency of the converter is low, and the reliable commutation of the valve arm restricts the safe and stable operation of the direct current transmission system. SUMMARY

[0004] The main purpose of the present application is to provide a current source converter, a control method and a system to at least solve the problem of low commutation efficiency of the current source converter in the prior art.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a current source converter is provided, comprising: a first bridge arm module and a second bridge arm module, the first bridge arm module comprising a plurality of first bridge arms, the second bridge arm module comprising a plurality of second bridge arms, wherein each output terminal of a three-phase power supply is connected with one first bridge arm in the first bridge arm module and one second bridge arm in the second bridge arm module respectively, each first bridge arm comprises a plurality of first power devices respectively, and each second bridge arm comprises a plurality of second power devices respectively; at least one first auxiliary module connected at least partially on the first bridge arm and electrically connected with the first pole of the first power device, for providing commutation voltage compensation for the first bridge arm with fault; at least one second auxiliary module connected at least partially on the second bridge arm and electrically connected with the second pole of the second power device, for providing commutation voltage compensation for the second bridge arm with fault.

[0006] Optionally, the current source converter further comprises a plurality of target inductors, a first end of one target inductor is connected to one output of the three-phase power supply respectively, a second end of one target inductor is connected to one first bridge arm and one second bridge arm respectively, the current source converter comprises a plurality of first auxiliary modules and a plurality of second auxiliary modules, wherein, one first auxiliary module is connected in series between the first pole of the first power device of the first bridge arm and one target inductor, the second pole of the first power device is electrically connected to the negative bus, one second auxiliary module is connected in series between the second pole of the second power device of the second bridge arm and one target inductor, the first pole of the second power device is electrically connected to the positive bus.

[0007] Optionally, each of the first auxiliary module and the second auxiliary module comprises a positive voltage applying unit and a negative voltage applying unit, the positive voltage applying unit comprises a first switch unit and a first capacitor connected in series, the negative voltage applying unit comprises a second switch unit and the first capacitor connected in series, in the first auxiliary module, one end of the positive voltage applying unit close to the positive pole of the first capacitor is electrically connected to one target inductor, and the other end of the positive voltage applying unit close to the negative pole of the first capacitor is electrically connected to the first power device; in the second auxiliary module, one end of the positive voltage applying unit close to the positive pole of the first capacitor is electrically connected to the second power device, and the other end of the positive voltage applying unit close to the negative pole of the first capacitor is electrically connected to one target inductor, when a fault occurs, the positive voltage applying unit is used to apply a forward voltage to the fault bridge arm, and the negative voltage applying unit is used to apply a reverse voltage to the target commutation bridge arm.

[0008] Optionally, the first switch unit comprises a first diode and a second diode, wherein, the cathode of the first diode is electrically connected to the positive pole of the first capacitor, the negative pole of the first capacitor is electrically connected to the anode of the second diode, in the first auxiliary module, the anode of the first diode is electrically connected to one target inductor, and the cathode of the second diode is electrically connected to the first power device, in the second auxiliary module, the anode of the first diode is electrically connected to the second power device, and the cathode of the second diode is electrically connected to one target inductor.

[0009] Optionally, the second switch unit comprises a first fully controlled device and a second fully controlled device, wherein, the second pole of the first fully controlled device is electrically connected to the negative pole of the first capacitor, the positive pole of the first capacitor is electrically connected to the first pole of the second fully controlled device, in the first auxiliary module, the first pole of the first fully controlled device is electrically connected to one target inductor, and the second pole of the second fully controlled device is electrically connected to the first power device, in the second auxiliary module, the first pole of the first fully controlled device is electrically connected to the second power device, and the second pole of the second fully controlled device is electrically connected to one target inductor.

[0010] Optionally, the current source converter comprises a first auxiliary module and a second auxiliary module, the first auxiliary module is connected between the first power devices of the first bridge arms and the positive bus, and the second auxiliary module is connected between the second power devices of the second bridge arms and the negative bus.

[0011] Optionally, the first auxiliary module and the second auxiliary module each comprise a first sub auxiliary unit, a second sub auxiliary unit, a third sub auxiliary unit and a second capacitor, the first sub auxiliary unit, the second sub auxiliary unit, the third sub auxiliary unit and the second capacitor are connected in parallel, and the first sub auxiliary unit, the second sub auxiliary unit and the third sub auxiliary unit are used to provide the fault bridge arm with forward voltage compensation by the second capacitor when a fault occurs.

[0012] Optionally, each of the first sub auxiliary unit, the second sub auxiliary unit and the third sub auxiliary unit comprises a third controllable device, a fourth controllable device and a fifth controllable device, the second pole of the third controllable device of the first auxiliary module is electrically connected with the first power device, the first pole of the third controllable device is electrically connected with the positive bus and the first pole of the fourth controllable device respectively, the second pole of the third controllable device of the second auxiliary module is electrically connected with the negative bus, the first pole of the third controllable device is electrically connected with the second power device and the first pole of the fourth controllable device respectively, the second pole of the fourth controllable device of the first auxiliary module and the second auxiliary module is electrically connected with the first end of the second capacitor, the first pole of the fifth controllable device is electrically connected with the second end of the second capacitor, and the second pole of the fifth controllable device is electrically connected with the second pole of the third controllable device.

[0013] According to another aspect of the present application, a control method of a current source converter is provided, the current source converter is used for control, and the control method comprises: controlling the current source converter to start, and pre-charging an auxiliary module of the current source converter; detecting operation information of an alternating current power grid of the current source converter, the operation information indicating whether a fault occurs in the alternating current power grid; in the case that the fault occurs in the alternating current power grid, controlling a target auxiliary module in the current source converter to apply a compensation voltage to a fault bridge arm, wherein the target auxiliary module is a first auxiliary module or a second auxiliary module corresponding to the fault bridge arm.

[0014] Optionally, the auxiliary module of the current source converter comprises a plurality of first auxiliary modules and a plurality of second auxiliary modules, each of the first auxiliary module and the second auxiliary module comprises: a positive voltage application unit and a negative voltage application unit, the positive voltage application unit comprises a first switch unit and a first capacitor connected in series, and the negative voltage application unit comprises a second switch unit and the first capacitor connected in series; in the first auxiliary module, one end of the positive voltage application unit close to the positive electrode of the first capacitor is electrically connected with a target inductor, the other end of the positive voltage application unit close to the negative electrode of the first capacitor is electrically connected with a first power device, one end of the negative voltage application unit close to the negative electrode of the first capacitor is electrically connected with the target inductor, and the other end of the negative voltage application unit close to the positive electrode of the first capacitor is electrically connected with the first power device; in the second auxiliary module, one end of the positive voltage application unit close to the positive electrode of the first capacitor is electrically connected with a second power device, the other end of the positive voltage application unit close to the negative electrode of the first capacitor is electrically connected with a target inductor, one end of the negative voltage application unit close to the negative electrode of the first capacitor is electrically connected with the second power device, and the other end of the negative voltage application unit close to the positive electrode of the first capacitor is electrically connected with the target inductor, in the case of a fault of the AC power grid, the target auxiliary module in the current source converter applies a compensation voltage to the fault bridge arm, comprising: controlling the first switch unit of the target auxiliary module of the fault bridge arm to be turned on and the second switch unit to be turned off, so as to turn on the positive voltage application unit, the first capacitor applies a positive compensation voltage to the fault bridge arm, controlling the first switch unit of the target auxiliary module of the target commutation bridge arm to be turned off and the second switch unit to be turned on, so as to turn on the negative voltage application unit, the first capacitor applies a negative compensation voltage to the target commutation bridge arm, wherein the positive compensation voltage and the negative compensation voltage form zero voltage turn-off between the fault bridge arm and the target commutation bridge arm, and the commutation is completed.

[0015] Optionally, the current source converter comprises a first auxiliary module and a second auxiliary module, the first auxiliary module is connected between the first power devices of the first bridge arms and the positive bus, the second auxiliary module is connected between the second power devices of the second bridge arms and the negative bus, the first auxiliary module and the second auxiliary module each comprise a first sub auxiliary unit, a second sub auxiliary unit, a third sub auxiliary unit and a second capacitor, the first sub auxiliary unit, the second sub auxiliary unit and the third sub auxiliary unit are connected in parallel with the second capacitor, each of the first sub auxiliary unit, the second sub auxiliary unit and the third sub auxiliary unit comprises: a third controllable device, a fourth controllable device and a fifth controllable device, the second pole of the third controllable device of the first auxiliary module is electrically connected with the first power device, the first pole of the third controllable device is electrically connected with the positive bus and the first pole of the fourth controllable device respectively, the second pole of the third controllable device of the second auxiliary module is electrically connected with the negative bus, the first pole of the third controllable device is electrically connected with the second power device and the first pole of the fourth controllable device respectively, the second pole of the fourth controllable device of the first auxiliary module and the second auxiliary module is electrically connected with the first end of the second capacitor, the first pole of the fifth controllable device is electrically connected with the second end of the second capacitor, the second pole of the fifth controllable device is electrically connected with the second pole of the third controllable device, in the case that the first auxiliary module and the second auxiliary module each comprise the second capacitor, the control method further comprises: controlling the third controllable device of the target auxiliary module located in the fault bridge arm to be turned off, the fourth controllable device and the fifth controllable device to be turned on, so as to make the second capacitor provide compensation voltage for the fault bridge arm; before the fault bridge arm recovers conduction, controlling the third controllable device and the fourth controllable device to be turned on, and controlling the fifth controllable device of the adjacent parallel bridge arm to be turned on, so as to discharge the second capacitor.

[0016] According to still another aspect of the present application, a current source converter system is provided, comprising a controller and a current source converter, the controller is configured to perform the control method of the current source converter.

[0017] With the technical solution of the application, the current source converter comprises a first bridge arm module, a second bridge arm module, at least one first auxiliary module and at least one second auxiliary module, wherein at least part of the at least one first auxiliary module is electrically connected to the first poles of the plurality of first power devices of the first bridge arm of the first bridge arm module, and at least part of the at least one second auxiliary module is electrically connected to the second poles of the plurality of second power devices of the second bridge arm of the second bridge arm module. By introducing the first auxiliary module and the second auxiliary module at specific positions in the first bridge arm module and the second bridge arm module of the current source converter, the bridge arm voltage can be actively adjusted to prevent overvoltage and overcurrent from causing damage to the power devices, and normal commutation can be performed. The first auxiliary module and the second auxiliary module can provide commutation compensation voltage for the fault bridge arm in abnormal conditions such as AC voltage drop and short circuit, provide voltage support to avoid bridge arm voltage collapse, help the fault bridge arm to be successfully turned off, make the current smoothly transfer to the target commutation bridge arm to complete commutation, improve the commutation efficiency, and solve the problem of low commutation efficiency of the current source converter in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0018] The drawings accompanying the specification of the present application form a part thereof, serve to provide further understanding of the application, and together with the description of the exemplary embodiments of the present application, serve to explain the present application, and do not constitute any improper limitation to the present application. In the drawings:

[0019] Figure 1 A structure schematic diagram of a first current source converter provided in an embodiment of the present application is shown;

[0020] Figure 2 A structure schematic diagram of a second current source converter provided in an embodiment of the present application is shown;

[0021] Figure 3 A structure schematic diagram of a first auxiliary module of the current source converter is shown; Figure 1

[0022] A structure schematic diagram of a second auxiliary module of the current source converter is shown; Figure 4 Figure 1 A structure schematic diagram of a first auxiliary module of the current source converter is shown;

[0023] Figure 5 Figure 2 A structure schematic diagram of a second auxiliary module of the current source converter is shown;

[0024] Figure 6 A structure schematic diagram of a first auxiliary module of the current source converter is shown; Figure 2

[0025] Figure 7 ​​​A flowchart of a control method of a first current source type converter is shown;

[0026] Figure 8 A flowchart of a control method of a second current source type converter is shown;

[0027] Figure 9 A flowchart of a control method of a third current source type converter is shown.

[0028] Wherein, the above drawings include the following reference signs:

[0029] 10, first bridge arm module; 11, first bridge arm; 12, first power device; 13, first power component; 14, second power component; 20, second bridge arm module; 21, second bridge arm; 22, second power device; 30, three-phase power supply; 41, first auxiliary module; 42, positive voltage application unit; 43, negative voltage application unit; 44, first sub-auxiliary unit; 45, second sub-auxiliary unit; 46, third sub-auxiliary unit; 51, second auxiliary module; 60, target inductance. DETAILED DESCRIPTION

[0030] 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.

[0031] 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. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0032] 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 "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including 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.

[0033] As introduced in the background, in the prior art, the high-voltage converter valve with high-voltage and high-power devices scaled in series has difficulty in effectively controlling the current discontinuity and the voltage across the bridge or between the devices during commutation, which easily leads to voltage and current fluctuation, affecting the stability of the system and the output quality. To solve the problem of low commutation efficiency of the current source converter in the prior art, the embodiments of the present application provide a current source converter, a control method and a system.

[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] According to an aspect of the embodiments of the present application, a current source converter is provided, as shown in Figure 1 and Figure 2 including: a first bridge arm module 10 and a second bridge arm module 20, the first bridge arm module 10 including a plurality of first bridge arms 11, and the second bridge arm module 20 including a plurality of second bridge arms 21, wherein each output terminal of a three-phase power supply 30 is connected to one first bridge arm 11 in the first bridge arm module 10 and one second bridge arm 21 in the second bridge arm module 20, respectively, each first bridge arm 11 including a plurality of first power devices 12, and each second bridge arm 21 including a plurality of second power devices 22; at least one first auxiliary module 41 connected at least partially to the first bridge arms and electrically connected to the first poles of the first power devices 12, for providing commutation voltage compensation for the faulty first bridge arms 11; and at least one second auxiliary module 51 connected at least partially to the second bridge arms and electrically connected to the second poles of the second power devices 22, for providing commutation voltage compensation for the faulty second bridge arms 21.

[0036] By introducing the first auxiliary module and the second auxiliary module at specific positions in the first bridge arm module and the second bridge arm module of the current source converter, the bridge arm voltage can be actively adjusted to prevent overvoltage and overcurrent from causing damage to the power devices, and normal commutation can be performed. The first auxiliary module and the second auxiliary module can provide commutation compensation voltage for the faulty bridge arms in time under abnormal conditions such as AC voltage drop and short circuit, which can avoid the commutation failure of the traditional current source converter, provide voltage support to avoid bridge arm voltage collapse, help the faulty bridge arm to be successfully turned off, make the current smoothly transfer to the target commutation bridge arm to complete commutation, improve the commutation efficiency, and solve the problem of low commutation efficiency of the current source converter in the prior art.

[0037] In the above embodiments, the current source converter of the application can adopt a three-phase six-bridge-arm structure, i.e., each phase is composed of a first bridge arm and a second bridge arm, and a plurality of power components are connected in series inside the bridge arm to meet the large current demand. The power components of each bridge arm are composed of power semiconductor devices and snubber circuits, such as IGBT (Insulated Gate Bipolar Transistor), IGCT (Integrated Gate-Commutated Thyristor) or thyristor, to adapt to the commutation requirements under different working conditions and realize flexible control of the current path. The snubber circuit can be an RC circuit (capacitor and resistor connected in series) or an RCD circuit (capacitor and resistor connected in series, and diode and resistor connected in parallel) to absorb the redundant current generated by the power semiconductor device during switching. As shown in FIG. 1, the current source converter in the application includes a first power component 13 and a second power component 14, the first power component 13 includes a plurality of first power devices 12 and a snubber circuit connected in parallel thereto, and the second power component 14 includes a plurality of second power devices 22 and a snubber circuit connected in parallel thereto. Figure 1

[0038] The at least part of the first auxiliary module is connected to the first bridge arm, which can be a first auxiliary module integrally connected to a first bridge arm, or a first part of the first auxiliary module connected to a first first bridge arm, a second part of the first auxiliary module connected to a second first bridge arm, and a third part of the first auxiliary module connected to a third first bridge arm. The specific connection relationship can not be limited thereto.

[0039] Under fault conditions, the conventional converter bridge arm adopts semi-controlled devices, and the reverse pressure holding time should be greater than the device ionization time. At the same time, it cannot be actively turned off during system failure, and may not be turned off in time due to the collapse of the alternating current grid voltage, which will directly lead to commutation failure and system power interruption, and even damage the power device. The application can provide a smooth bridge arm voltage transition during normal commutation, and can quickly switch to a compensation mode under fault conditions, effectively avoiding commutation failure and protecting the power device. Compared with the prior art, the auxiliary module of the application has a simple structure and flexible control, reduces the overall size and cost of the converter, improves the operation stability of the current source converter system, especially the adaptability to high dynamic and strong fault conditions, realizes high efficiency, high reliability and active protection of the current source converter, and provides a safer and more flexible commutation solution for the direct current transmission system.

[0040] ​The setting positions of the first auxiliary module and the second auxiliary module are different, and the commutation processes of the current source converter are also different. The application provides two setting conditions of the auxiliary modules, wherein the first condition is as follows: in some optional embodiments, as shown in Figure 1 , the current source converter further includes a plurality of target inductors 60, a first end of each target inductor 60 is connected to an output end of the three-phase power supply 30, a second end of each target inductor 60 is connected to a first bridge arm and a second bridge arm, the current source converter includes a plurality of first auxiliary modules 41 and a plurality of second auxiliary modules 51, wherein one first auxiliary module 41 is connected in series between the first end of one target inductor 60 and the first pole of the first power device 12 of the first bridge arm 11, the second pole of the first power device 12 is electrically connected to the negative bus, and one second auxiliary module 51 is connected in series between the second end of one target inductor 60 and the second pole of the second power device 22 of the second bridge arm 21, and the first pole of the second power device 22 is electrically connected to the positive bus. By connecting an auxiliary module in series in each bridge arm, the auxiliary module of the corresponding bridge arm can be switched to different working modes (such as forward / reverse voltage mode) when commutation is needed, and the current smoothing blocking and transfer can be realized through the combination between the auxiliary module of the fault bridge arm and the auxiliary module of the target commutation bridge arm. For example, the auxiliary module of the fault bridge arm is switched to the forward voltage mode in the fault state, and the auxiliary module of the target commutation bridge arm (normal bridge arm) is switched to the reverse voltage mode, so that zero voltage is formed between the two bridge arms, the zero voltage commutation is realized, and the overcurrent and overvoltage impact on the power device are avoided. Through flexible auxiliary module control, not only the efficient commutation under normal working condition is ensured, but also the voltage can be actively regulated to realize reliable system protection when the device or bridge arm fails.

[0041] In the above optional embodiments, the first bridge arm module and the first auxiliary module are the structures of the lower half part in Figure 1 , and the second bridge arm module and the second auxiliary module are the structures of the upper half part in Figure 1 , as shown in Figure 1 , an inductor is further connected in series between the plurality of power devices in each bridge arm and the bus. The inductor can smooth the current change in the turn-on and turn-off processes of the power device, and avoid the instantaneous jump of the current, which helps to reduce the current harmonic and improve the power quality of the converter. In addition, the inductor can also cooperate with the auxiliary module to improve the voltage waveform in the commutation process by controlling the energy stored in the inductor, so as to realize more efficient and more stable commutation.

[0042] In order to better realize the zero voltage commutation of the current converter during commutation, in some optional embodiments, as shown in Figure 1 , Figure 3 , and Figure 4As shown, each of the first auxiliary module and the second auxiliary module includes a positive voltage application unit 42 and a negative voltage application unit 43, the positive voltage application unit 42 includes a first switch unit and a first capacitor C1 connected in series, and the negative voltage application unit 43 includes a second switch unit and the first capacitor C1 connected in series; in the first auxiliary module 41, one end of the positive voltage application unit 42 close to the positive pole of the first capacitor C1 is electrically connected with a target inductor 60, and the other end of the positive voltage application unit 42 close to the negative pole of the first capacitor C1 is electrically connected with the first power device 12; in the second auxiliary module 51, one end of the positive voltage application unit 42 close to the positive pole of the first capacitor C1 is electrically connected with the second power device 22, and the other end of the positive voltage application unit 42 close to the negative pole of the first capacitor C1 is electrically connected with a target inductor 60, when a fault occurs, the positive voltage application unit 42 is used to apply a forward voltage to the fault bridge arm, and the negative voltage application unit 43 is used to apply a reverse voltage to the target commutation bridge arm. Wherein, when a fault occurs, by controlling the first switch unit of the auxiliary module corresponding to the fault bridge arm to be turned on and the second switch unit to be turned off, the positive voltage application unit 42 applies a forward voltage to the fault bridge arm during commutation, and by controlling the first switch unit of the auxiliary module corresponding to the target commutation bridge arm to be turned off and the second switch unit to be turned on, the negative voltage application unit 43 applies a reverse voltage to the target commutation bridge arm. In this way, the auxiliary module can actively adjust the voltage between the bridge arms, and the smooth transfer of current can be realized. The connection of the positive and negative voltage units and the target inductor (three-phase inductor) enables quick response during commutation, provides timely voltage compensation, and avoids the current sensor system failure caused by commutation failure.

[0043] In some optional embodiments, as Figure 3 and Figure 4As shown, the first switch unit includes: a first diode D1 and a second diode D2, wherein the cathode of the first diode D1 is electrically connected with the positive pole of the first capacitor C1, the negative pole of the first capacitor C1 is electrically connected with the anode of the second diode D2, in the first auxiliary module, the anode of the first diode D1 is electrically connected with a target inductor, the cathode of the second diode D2 is electrically connected with the first power device, in the second auxiliary module, the anode of the first diode D1 is electrically connected with the second power device, and the cathode of the second diode D2 is electrically connected with a target inductor. Wherein, when the bridge arm commutation is performed, the auxiliary module of the exiting valve bridge arm (the fault bridge arm when the fault commutation is performed) provides a forward voltage for the exiting valve bridge arm, the first diode D1 and the second diode D2 are turned on, the main current passes through the first diode D1, the first capacitor C1 and the second diode D2 to enter the bridge arm, so that the auxiliary module operates in the forward voltage mode, at this time, the auxiliary module applies a forward voltage along the main current direction of the exiting valve bridge arm, and provides voltage compensation when the exiting valve bridge arm fails or breaks. The positive voltage application unit 42 adopts the combination of diodes and capacitors, can provide forward voltage compensation in the commutation process, realizes smooth transfer of the current, effectively avoids commutation failure, protects the power device from overvoltage damage, and improves the self-recovery ability of the converter under fault conditions.

[0044] In some optional embodiments, as Figure 3 and Figure 4As shown, the second switch unit includes: a first fully controlled device T1 and a second fully controlled device T2, wherein the second pole of the first fully controlled device T1 is electrically connected with the negative pole of the first capacitor C1, the positive pole of the first capacitor C1 is electrically connected with the first pole of the second fully controlled device T2, in the first auxiliary module, the first pole of the first fully controlled device T1 is electrically connected with a target inductor, the second pole of the second fully controlled device T2 is electrically connected with the first power device, in the second auxiliary module, the first pole of the first fully controlled device T1 is electrically connected with the second power device, and the second pole of the second fully controlled device T2 is electrically connected with a target inductor. When the bridge arm commutation is performed, the auxiliary module provides a forward voltage for the exit valve bridge arm and a target commutation bridge arm, and also provides a negative voltage for the target commutation bridge arm, so that the first fully controlled device T1 and the second fully controlled device T2 of the negative voltage application unit 43 are turned on, the main current flows through the first fully controlled device T1, the first capacitor C1 and the second fully controlled device T2 into the target commutation bridge arm, and the operation is in a reverse voltage mode. The auxiliary module applies a reverse voltage to the target commutation bridge arm, and when the target commutation bridge arm participates in commutation, the reverse voltage and the forward voltage are superimposed to cooperate with each other to reduce the commutation difficulty. The negative voltage application unit 43 can actively apply reverse voltage compensation in the commutation process through the cooperative work of the fully controlled device and the capacitor, optimizes the commutation process, especially in the fault switching, can effectively suppress the voltage overshoot, cooperates with the positive voltage application unit to realize zero voltage turn-off, protects the safety of the power device, and enhances the reliability of the system.

[0045] In the above optional embodiments, as shown in Figure 3 and Figure 4 As shown, when the converter does not need to commutate and is in normal operation, the first fully controlled device T1 and the second diode D2 of the auxiliary module are turned on, and other devices are turned off, so that the auxiliary module operates in a bypass mode, the main current enters the bridge arm through the first fully controlled device T1 and the second diode D2, and other branches in the auxiliary module are equivalent to short circuits, and no additional voltage is provided, which has no effect on normal operation. In this way, the auxiliary module can be put into the circuit to work when needed, and the loss can be reduced.

[0046] The second auxiliary module is set as follows: in some optional embodiments, as shown in Figure 2As shown, the current source converter includes a first auxiliary module 41 and a second auxiliary module 51, the first auxiliary module 41 is connected between the plurality of first power devices of the plurality of first bridge arms 11 and the positive bus, and the second auxiliary module 51 is connected between the plurality of second power devices 22 of the plurality of second bridge arms 21 and the negative bus. The above scheme adopts fewer auxiliary modules, and can also compensate the current of the fault bridge arm in time when a fault occurs. The converter proposed in the present application can adopt the above-mentioned first and second auxiliary module settings, so that the converter can be flexibly adjusted according to the actual application scene, and is more widely applicable. The above-mentioned first power device and second power device 22 can be a semi-controlled or fully-controlled device. The above-mentioned first bridge arm module 10 including a plurality of first bridge arms 11 is a structure as shown in the upper half of Figure 2 , and the second bridge arm module 20 including a plurality of second bridge arms 21 is a structure as shown in the lower half of Figure 2 .

[0047] In some optional embodiments, as shown in Figure 5 , the first auxiliary module and the second auxiliary module each include a first sub-auxiliary unit 44, a second sub-auxiliary unit 45, a third sub-auxiliary unit 46, and a second capacitor C2, the first sub-auxiliary unit 44, the second sub-auxiliary unit 45, the third sub-auxiliary unit 46, and the second capacitor C2 are connected in parallel, and the first sub-auxiliary unit 44, the second sub-auxiliary unit 45, and the third sub-auxiliary unit 46 are used to provide the second capacitor C2 with forward voltage compensation for the fault bridge arm when a fault occurs. The above-mentioned first sub-auxiliary unit 44, second sub-auxiliary unit 45, and third sub-auxiliary unit 46 are structures connected with the second bridge arm in phase A, phase B, and phase C in Figure 2 , and the second capacitor C2 is an element for providing commutation voltage. The above-mentioned first sub-auxiliary unit 44, second sub-auxiliary unit 45, third sub-auxiliary unit 46, and second capacitor C2 constitute an inter-phase auxiliary module of the converter, and in the first bridge arm module, the above-mentioned inter-phase auxiliary module connects the plurality of first bridge arms in series with the positive bus, and in the second bridge arm module, the above-mentioned inter-phase auxiliary module connects the plurality of second bridge arms in series with the negative bus. The parallel structure of the inter-phase auxiliary module can enhance the voltage compensation capability in the commutation process, reduce the current interruption, ensure the smooth transfer of the current, and improve the operation efficiency and system stability of the converter.

[0048] In some optional embodiments, as shown in Figure 6As shown, each first sub auxiliary unit, each second sub auxiliary unit and each third sub auxiliary unit comprises: a third fully controlled device (Ka1, Kb1 and Kc1), a fourth fully controlled device (Ka2, Kb2 and Kc2) and a fifth fully controlled device (Ka3, Kb3 and Kc3), the second pole of the third fully controlled device (Ka1, Kb1 and Kc1) of the first auxiliary module is electrically connected with the first power device (for example, Ka1 is electrically connected with the first power device in phase A, Kb1 is electrically connected with the first power device in phase B, and Kc1 is electrically connected with the first power device in phase C), the first pole of the third fully controlled device (Ka2, Kb2 and Kc2) is respectively electrically connected with the positive bus and the first pole of the fourth fully controlled device (Ka2, Kb2 and Kc2), the second pole of the third fully controlled device (Ka1, Kb1 and Kc1) of the second auxiliary module is electrically connected with the negative bus, the first pole of the third fully controlled device (Ka1, Kb1 and Kc1) is respectively electrically connected with the second power device and the first pole of the fourth fully controlled device (Ka2, Kb2 and Kc2), the second pole of the fourth fully controlled device (Ka2, Kb2 and Kc2) of the first auxiliary module and the second auxiliary module is electrically connected with the first end of the second capacitor C2, the first pole of the fifth fully controlled device (Ka3, Kb3 and Kc3) is electrically connected with the second end of the second capacitor C2, and the second pole of the fifth fully controlled device (Ka3, Kb3 and Kc3) is electrically connected with the second pole of the third fully controlled device (Ka1, Kb1 and Kc1). Through the mutual cooperation between the above fully controlled devices, the second capacitor C2 completes the capacitor compensation for the fault bridge arm in the fault commutation condition, and provides a support voltage for the fault bridge arm, so that it commutes smoothly.

[0049] The operation mode of the auxiliary circuit is illustrated by taking the normal operation and commutation process of the AB two-phase as an example. In the normal operation, Ka1, Kb1 and Kc1 are turned on, and the rest of the devices are turned off. At this time, the second capacitor C2 does not enter the circuit and is in a bypass state. The three-phase bridge arm is normally conducting, and the converter is normally operating. In the fault commutation, the inter-phase auxiliary module will switch the second capacitor C2 according to the AC voltage drop condition through the turn-on and turn-off of the fully controlled devices, thereby compensating the commutation voltage. Taking the commutation process from the A phase to the B phase as an example, the exit valve bridge arm Ka2 and Ka3 of the A phase are turned on, Ka1 is turned off, the entry valve bridge arm Kb2 of the B phase is turned on, Kb1 and Kb3 are turned off, at this time, the second capacitor C2 provides a forward commutation voltage for the exit valve bridge arm to compensate the voltage. After the forward voltage compensation of the exit valve bridge arm, the third fully controlled device Ka1 and the fourth fully controlled device Ka2 of the exit valve bridge arm are turned on, the fifth fully controlled device Ka3 is turned off, the third fully controlled device Kb1 and the fifth fully controlled device Kb3 of the target commutation bridge arm are turned on, and the fourth fully controlled device Kb2 is turned off, so as to provide a negative voltage for the target commutation bridge arm to accelerate the commutation, and the second capacitor C2 can also be discharged to reset before the exit valve bridge arm is turned on.

[0050] A control method of a current source converter operated in a mobile terminal, a computer terminal or similar computing device is provided in the embodiment. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0051] In some embodiments, temperature sensors and current sensors can also be built in the current source converter to monitor the working state of the power devices. After the AC power grid fails, the temperature and current of the power devices are detected. If the temperature of a certain power device reaches or exceeds a preset temperature threshold value, which represents the safe maximum temperature limit of the power device during operation, or the current reaches or exceeds a preset current threshold value, which represents the maximum current that the power device can withstand, the control switches the fault power device from the on state to the off state to cut off the current path through the device, removes the fault power device with temperature and / or current exceeding the normal range, and reduces the heat and additional loss of the device, while ensuring that the commutation can be maintained.

[0052] In some embodiments, the current source converter can further comprise an energy recovery unit, one end of the energy recovery unit being electrically connected to the target inductor in the target auxiliary module, and the other end being electrically connected to the second capacitor or the first capacitor, for recovering the excess energy in the auxiliary loop during commutation to reduce energy loss. The energy recovery unit can be composed of an energy converter and an energy storage element (such as a super capacitor), and after commutation is completed, the energy not consumed in the auxiliary module is recovered by the energy converter and stored in the energy storage element for subsequent commutation. In this way, energy waste can be reduced, the pre-charging process of the auxiliary module can be supported by recovering energy, and the dependence on grid energy is reduced.

[0053] Figure 7 is a flowchart of a control method of a current source converter according to an embodiment of the present application. As shown in Figure 7 the method comprises the following steps:

[0054] Step S1, controlling the current source converter to start and pre-charging the auxiliary module of the current source converter;

[0055] Specifically, before starting the current source converter, the capacitor in the auxiliary commutation module is first pre-charged to ensure that there is enough energy to support voltage compensation during commutation. The pre-charging process can improve the controllability and efficiency of commutation, ensure that the auxiliary module is ready at the beginning of commutation, can immediately respond to the commutation action to provide voltage compensation, avoid commutation failure, and improve the operation stability and reliability of the system.

[0056] Step S2, detecting the operation information of the alternating current grid of the current source converter, the operation information indicating whether a fault occurs in the alternating current grid;

[0057] Specifically, the grid operation state includes but is not limited to voltage drop, short circuit, frequency fluctuation, etc. Fault detection can provide early warning and trigger the auxiliary commutation to work, ensuring that the converter can still operate safely and stably when the grid is abnormal, and improving the anti-interference ability and fault self-recovery ability of the system.

[0058] Step S3, in the case where the alternating current grid fails, controlling the target auxiliary module in the current source converter to apply a compensation voltage to the fault bridge arm, wherein the target auxiliary module is the first auxiliary module or the second auxiliary module corresponding to the fault bridge arm;

[0059] Specifically, when the fault detection confirms that the AC power grid is faulty, the target auxiliary module which is in operation and corresponds to the fault bridge arm is controlled to enter an operating state. The auxiliary module entering the operating state can be divided into two cases. In the first case, for the fault bridge arm, the auxiliary module operates in a forward voltage mode, and for the non-fault bridge arm, the auxiliary module operates in a reverse voltage mode. In the second case, only for the fault bridge arm, the auxiliary module operates in a forward voltage mode to perform forward voltage compensation for the fault bridge arm. This control strategy can actively adjust the bridge arm voltage according to the specific situation of the power grid fault, avoid commutation failure, and protect the power device.

[0060] Through the above control method, the current source converter is controlled to apply compensation voltage to the fault bridge arm to successfully complete commutation. When the AC power grid is faulty, the target auxiliary module can actively adjust the bridge arm voltage to prevent overvoltage and overcurrent from damaging the power device, and can perform normal commutation. The target auxiliary module can provide voltage compensation for the fault bridge arm, provide voltage support to avoid bridge arm voltage collapse, help the fault bridge arm to smoothly turn off, make the current smoothly transfer to the target commutation bridge arm to complete commutation, improve the commutation efficiency, and improve the operation stability and safety of the converter under fault conditions.

[0061] In the auxiliary module of the current source converter, the auxiliary module includes a plurality of first auxiliary modules and a plurality of second auxiliary modules, each of the first auxiliary module and the second auxiliary module includes a positive voltage applying unit and a negative voltage applying unit, the positive voltage applying unit includes a first switch unit and a first capacitor connected in series, and the negative voltage applying unit includes a second switch unit and the first capacitor connected in series; in the first auxiliary module, one end of the positive voltage applying unit close to a positive electrode of the first capacitor is electrically connected with a target inductor, one end of the positive voltage applying unit close to a negative electrode of the first capacitor is electrically connected with a first power device, one end of the negative voltage applying unit close to the negative electrode of the first capacitor is electrically connected with the target inductor, and one end of the negative voltage applying unit close to the positive electrode of the first capacitor is electrically connected with the first power device; in the second auxiliary module, one end of the positive voltage applying unit close to the positive electrode of the first capacitor is electrically connected with a second power device, one end of the positive voltage applying unit close to the negative electrode of the first capacitor is electrically connected with the target inductor, one end of the negative voltage applying unit close to the negative electrode of the first capacitor is electrically connected with the second power device, and one end of the negative voltage applying unit close to the positive electrode of the first capacitor is electrically connected with the target inductor; and step S3, in the case that the AC power grid is faulty, controlling the target auxiliary module in the current source converter to apply compensation voltage to the fault bridge arm, comprising:

[0062] The first switch unit of the target auxiliary module of the fault bridge arm is turned on and the second switch unit is turned off to turn on the positive voltage application unit, the first capacitor applies a positive compensation voltage to the fault bridge arm, the first switch unit of the target auxiliary module of the target commutation bridge arm is turned off and the second switch unit is turned on to turn on the negative voltage application unit, and the first capacitor applies a negative compensation voltage to the target commutation bridge arm; the first diode and the second diode of the target auxiliary module of the fault bridge arm are turned on, the first full-controlled device and the second full-controlled device are turned off, the main current passes through the first diode, the first capacitor and the second diode (the positive voltage application unit) into the bridge arm, and the auxiliary module operates in the positive voltage mode, at this time, the auxiliary module applies a positive voltage along the main current direction of the fault bridge arm to provide positive voltage compensation for the fault bridge arm. The first full-controlled device and the second full-controlled device of the target auxiliary module of the target commutation bridge arm are turned on, the first diode and the second diode are turned off, the main current flows through the first full-controlled device, the first capacitor and the second full-controlled device (the negative voltage application unit) into the target commutation bridge arm, and operates in the reverse voltage mode, the auxiliary module applies a reverse voltage to the target commutation bridge arm, and when the target commutation bridge arm participates in commutation, the reverse voltage and the positive voltage are superimposed to reduce the commutation difficulty. Zero voltage turn-off can make the converter avoid overcurrent and overvoltage impact, and safely complete commutation. The steps of providing positive voltage for the fault bridge arm and negative voltage for the target commutation bridge arm can be simultaneous, which can complete commutation faster.

[0063] Specifically, in the current source type converter, a first auxiliary module and a second auxiliary module are included, the first auxiliary module is connected between a plurality of first power devices of a plurality of first bridge arms and a positive bus, the second auxiliary module is connected between a plurality of second power devices of a plurality of second bridge arms and a negative bus, the first auxiliary module and the second auxiliary module each include a first sub auxiliary unit, a second sub auxiliary unit, a third sub auxiliary unit and a second capacitor, the first sub auxiliary unit, the second sub auxiliary unit and the third sub auxiliary unit and the second capacitor are connected in parallel, each of the first sub auxiliary unit, the second sub auxiliary unit and the third sub auxiliary unit includes a third unidirectional device, a fourth unidirectional device and a fifth unidirectional device, the second pole of the third unidirectional device of the first auxiliary module is electrically connected with the first power device, the first pole of the third unidirectional device is electrically connected with the positive bus and the first pole of the fourth unidirectional device respectively, the second pole of the third unidirectional device of the second auxiliary module is electrically connected with the negative bus, the first pole of the third unidirectional device is electrically connected with the second power device and the first pole of the fourth unidirectional device respectively, the second pole of the fourth unidirectional device of the first auxiliary module and the second auxiliary module is electrically connected with the first end of the second capacitor, the first pole of the fifth unidirectional device is electrically connected with the second end of the second capacitor, and the second pole of the fifth unidirectional device is electrically connected with the second pole of the third unidirectional device, first, pre-charge the auxiliary module of the converter, control the first unidirectional device T1 and the second unidirectional device T2 to be closed, charge the first capacitor through the first diode, and stop when the voltage of the first capacitor reaches the threshold value. Figure 8 As shown, when an AC fault occurs, the first unidirectional device T1 and the second unidirectional device T2 of the auxiliary module are controlled to be closed, the first diode D1 and the second diode D2 are turned on, the fault bridge arm is actively turned off, the auxiliary module applies a positive voltage (capacitor positive voltage input) to the fault bridge arm through the first capacitor to compensate the voltage of the fault bridge arm to actively turn off and build the commutation voltage to complete commutation, thereby resisting commutation failure; while applying a positive voltage to the fault bridge arm, the first unidirectional device T1 and the second unidirectional device T2 of the auxiliary module of the target commutation bridge arm are turned on, and the first diode D1 and the second diode D2 are turned off, so that the auxiliary module first capacitor applies a negative voltage to the target commutation bridge arm, accelerates the commutation speed of the fault bridge arm to the target commutation bridge arm, and resists commutation failure.

[0064] In the case that the first auxiliary module and the second auxiliary module both include the second capacitor, the control method further includes: controlling the third controllable device of the target auxiliary module in the fault bridge arm to be turned off, and the fourth controllable device and the fifth controllable device to be turned on, so as to provide a compensation voltage for the fault bridge arm by the second capacitor; when the bridge arm needs to be turned off, assuming that the A-phase bridge arm is actively turned off, the third controllable device Ka1 is controlled to be latched; the fourth controllable device Ka2 and the fifth controllable device Ka3 are controlled to be turned on, the current flows into the second capacitor C2 through Ka2, charges the second capacitor C2, and then flows into the bridge arm through Ka3. At the same time, the third controllable devices in the B-phase and the C-phase are controlled to be turned on, the current flows into the bridge arm through the third controllable devices, and the fourth controllable devices and the fifth controllable devices are controlled to be turned off. The forward voltage of the second capacitor C2 is applied to the A-phase bridge arm, a commutation voltage is constructed to complete commutation, and commutation failure is resisted.

[0065] Before the fault bridge arm is restored to be turned on, the third controllable device and the fourth controllable device are controlled to be turned on, and the fifth controllable device of the adjacent parallel bridge arm is controlled to be turned on, so as to discharge the second capacitor. For example, the A-phase bridge arm is the fault bridge arm, before the A-phase bridge arm is restored to be turned on, the third controllable device Ka1 and the fourth controllable device Ka2 of the auxiliary module of the A-phase bridge arm are controlled to be turned on, and the fifth controllable device Ka3 is controlled to be turned off, the third controllable device Kb1 and the fifth controllable device Kb3 of the auxiliary module of the B-phase bridge arm parallel to the A-phase bridge arm are controlled to be turned on, and the fourth controllable device Kb2 is controlled to be turned off, so as to discharge the second capacitor and reset, and prepare for the next commutation.

[0066] Specifically, first, the auxiliary module of the converter is pre-charged, the third controllable device Ka1 is controlled to be turned off, the fourth controllable device Ka2 and the fifth controllable device Ka3 are controlled to be turned on, the second capacitor is charged, and the charging is stopped until the voltage of the second capacitor reaches a threshold value. For example, Figure 9As shown, in the AC fault stage, active turn-off is required for the fault bridge arm, taking the first target bridge arm fault of phase A and commutation to the second target bridge arm of phase B as an example, first, the third fully controllable device Ka1 of the auxiliary module of the first target bridge arm is controlled to be closed, the fourth fully controllable device Ka2 and the fifth fully controllable device Ka3 are controlled to be turned on, Kb2 of the second target bridge arm is controlled to be turned on, and Kb1 and Kb3 are controlled to be turned off, so that the second capacitor of the auxiliary module applies a positive voltage to the first target bridge arm, to perform voltage compensation for the first target bridge arm to actively turn off and build a commutation voltage. Then, the third fully controllable device Ka1 and the fourth fully controllable device Ka2 of the first target bridge arm are controlled to be turned on, the fifth fully controllable device Ka3 is controlled to be turned off, the third fully controllable device Kb1 and the fifth fully controllable device Kb3 of the auxiliary module of the second target bridge arm are controlled to be turned on, and the fourth fully controllable device Kb2 is controlled to be turned off, so that the second capacitor applies a negative voltage to the second target bridge arm, to accelerate the speed of the first target bridge arm (the fault bridge arm) to the second target bridge arm (the target commutation bridge arm), resist commutation failure, and reset the voltage of the second capacitor of the auxiliary module after commutation is completed, so that the auxiliary module can continue to work when the current source converter generates a fault next time.

[0067] According to another embodiment of the present application, a current source converter system is provided, comprising a controller and the current source converter described above, and the controller is used to execute the control method of the current source converter described above.

[0068] By using the controller in the system to control the current source converter, when the current source converter fails, the first diode and the second diode of the target auxiliary module of the fault bridge arm are controlled to be turned on, the first fully controllable device and the second fully controllable device are controlled to be turned off, the main current enters the bridge arm through the first diode, the first capacitor and the second diode, and the auxiliary module operates in the positive voltage mode, at this time, the auxiliary module applies a positive voltage along the main current direction of the fault bridge arm, to provide positive voltage compensation for the fault bridge arm. The first fully controllable device and the second fully controllable device of the target auxiliary module of the target commutation bridge arm are controlled to be turned on, the first diode and the second diode are controlled to be turned off, the main current flows through the first fully controllable device, the first capacitor and the second fully controllable device to enter the target commutation bridge arm, and the auxiliary module operates in the reverse voltage mode, to apply a reverse voltage to the target commutation bridge arm. When the target commutation bridge arm participates in commutation, the reverse voltage and the positive voltage are superimposed to cooperate with each other to reduce the commutation difficulty, so that the current source converter can normally commutate when it fails, and thus the technical problem of low commutation efficiency of the current source converter is solved.

[0069] The technical features of the above embodiments can be combined arbitrarily, and to make the description concise, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present disclosure.

[0070] It should also be noted that the terms "comprising", "comprising" or any other variant thereof are intended to cover non-exclusive inclusions, so that a process, method, article or device that includes a list of elements not only includes those elements, but also includes other elements not explicitly listed, or inherent to such a process, method, article or device. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article or device that includes the element.

[0071] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects:

[0072] 1) The current source converter of the present application can actively regulate the bridge arm voltage by introducing the first auxiliary module and the second auxiliary module at a specific position in the first bridge arm module and the second bridge arm module of the current source converter, prevent overvoltage and overcurrent from causing damage to power devices, and can perform normal commutation. Among them, the first auxiliary module and the second auxiliary module can provide commutation compensation voltage for the fault bridge arm in abnormal conditions such as AC voltage drop and short circuit, provide voltage support to avoid bridge arm voltage collapse, help the fault bridge arm to shut down smoothly, make the current smoothly transfer to the target commutation bridge arm to complete commutation, improve the commutation efficiency, and solve the problem of low commutation efficiency of the current source converter in the prior art.

[0073] 2) In the case of the current source converter of the present application including a plurality of first auxiliary modules and a plurality of second auxiliary modules, the first auxiliary module and the second auxiliary module each include a positive voltage applying unit and a negative voltage applying unit. The positive voltage applying unit applies a forward voltage to the fault bridge arm during commutation, and the negative voltage applying unit applies a reverse voltage to the target commutation bridge arm. In this way, the auxiliary module can actively regulate the voltage between the bridge arms to achieve smooth transfer of current. The connection of the positive and negative voltage units with the target inductor (three-phase inductor) enables rapid response during commutation and provides timely voltage compensation to avoid current system failure caused by commutation failure.

[0074] 3) In the case of the current source converter of the present application including one first auxiliary module and one second auxiliary module, the first auxiliary module and the second auxiliary module each include a first sub-auxiliary unit, a second sub-auxiliary unit, a third sub-auxiliary unit and a second capacitor. The above four parts are connected in parallel with each other. Through the synergistic effect between the first sub-auxiliary unit, the second sub-auxiliary unit and the third sub-auxiliary unit, the voltage compensation of the fault bridge arm is completed, and the commutation is completed.

[0075] The above merely provides preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A current source converter, characterized in that, include: First bridge arm module and second bridge arm module, the first bridge arm module includes multiple first bridge arms, the second bridge arm module includes multiple second bridge arms, wherein each output terminal of the three-phase power supply is connected to one of the first bridge arms of the first bridge arm module and one of the second bridge arms of the second bridge arm module respectively, each first bridge arm includes multiple first power devices, and each second bridge arm includes multiple second power devices. At least one first auxiliary module, at least partially connected to the first bridge arm and electrically connected to the first pole of the first power device, is used to provide commutation voltage compensation for the faulty first bridge arm; At least one second auxiliary module, at least partially connected to the second bridge arm and electrically connected to the second pole of the second power device, is used to provide commutation voltage compensation for the faulty second bridge arm.

2. The current source converter according to claim 1, characterized in that, The current source converter also includes multiple target inductors. The first end of one of the target inductors is connected to one output terminal of the three-phase power supply, and the second end of one of the target inductors is connected to one of the first bridge arms and one of the second bridge arms. The current source converter includes multiple first auxiliary modules and multiple second auxiliary modules. One of the first auxiliary modules is connected in series between the first pole of the first power device and one of the target inductors, and the second pole of the first power device is electrically connected to the negative bus. One of the second auxiliary modules is connected in series between the second pole of the second power device in the second bridge arm and one of the target inductors, and the first pole of the second power device is electrically connected to the positive bus.

3. The current source converter according to claim 2, characterized in that, Each of the first auxiliary module and the second auxiliary module includes a positive voltage application unit and a negative voltage application unit. The positive voltage application unit includes a first switching unit and a first capacitor connected in series, and the negative voltage application unit includes a second switching unit and the first capacitor connected in series. In the first auxiliary module, the end of the positive voltage application unit near the positive terminal of the first capacitor is electrically connected to a target inductor, and the end of the positive voltage application unit near the negative terminal of the first capacitor is electrically connected to the first power device. The end of the negative voltage application unit near the negative terminal of the first capacitor is electrically connected to a target inductor. One end of the positive terminal is electrically connected to the first power device; in the second auxiliary module, the end of the positive voltage application unit near the positive terminal of the first capacitor is electrically connected to the second power device, the end of the positive voltage application unit near the negative terminal of the first capacitor is electrically connected to a target inductor, the end of the negative voltage application unit near the negative terminal of the first capacitor is electrically connected to the second power device, and the end of the negative voltage application unit near the positive terminal of the first capacitor is electrically connected to a target inductor. When a fault occurs, the positive voltage application unit is used to apply a positive voltage to the faulty bridge arm, and the negative voltage application unit is used to apply a reverse voltage to the target commutation bridge arm.

4. The current source converter according to claim 3, characterized in that, The first switching unit includes a first diode and a second diode, wherein the cathode of the first diode is electrically connected to the positive terminal of the first capacitor, and the negative terminal of the first capacitor is electrically connected to the anode of the second diode. In the first auxiliary module, the anode of the first diode is electrically connected to a target inductor, and the cathode of the second diode is electrically connected to the first power device. In the second auxiliary module, the anode of the first diode is electrically connected to the second power device, and the cathode of the second diode is electrically connected to a target inductor.

5. The current source converter according to claim 3, characterized in that, The second switching unit includes: a first fully controllable device and a second fully controllable device, wherein the second terminal of the first fully controllable device is electrically connected to the negative terminal of the first capacitor, and the positive terminal of the first capacitor is electrically connected to the first terminal of the second fully controllable device. In the first auxiliary module, the first terminal of the first fully controllable device is electrically connected to a target inductor, and the second terminal of the second fully controllable device is electrically connected to the first power device. In the second auxiliary module, the first terminal of the first fully controllable device is electrically connected to the second power device, and the second terminal of the second fully controllable device is electrically connected to a target inductor.

6. The current source converter according to claim 1, characterized in that, The current source converter includes a first auxiliary module and a second auxiliary module. The first auxiliary module is connected between a plurality of first power devices and a positive bus of a plurality of first bridge arms, and the second auxiliary module is connected between a plurality of second power devices and a negative bus of a plurality of second bridge arms.

7. The current source converter according to claim 6, characterized in that, Both the first auxiliary module and the second auxiliary module include: a first sub-auxiliary unit, a second sub-auxiliary unit, a third sub-auxiliary unit, and a second capacitor. The first sub-auxiliary unit, the second sub-auxiliary unit, the third sub-auxiliary unit, and the second capacitor are connected in parallel. In the event of a fault, the first sub-auxiliary unit, the second sub-auxiliary unit, and the third sub-auxiliary unit are used to enable the second capacitor to provide positive voltage compensation for the faulty bridge arm.

8. The current source converter according to claim 7, characterized in that, Each of the first sub-auxiliary units, each of the second sub-auxiliary units, and each of the third sub-auxiliary units includes: a third fully controllable device, a fourth fully controllable device, and a fifth fully controllable device. The second pole of the third fully controllable device in the first auxiliary module is electrically connected to the first power device, and the first pole of the third fully controllable device is electrically connected to the positive bus and the first pole of the fourth fully controllable device, respectively. The second pole of the third fully controllable device in the second auxiliary module is electrically connected to the negative bus, and the first pole of the third fully controllable device is electrically connected to the second power device and the first pole of the fourth fully controllable device, respectively. The second pole of the fourth fully controllable device in the first auxiliary module and the second auxiliary module is electrically connected to the first terminal of the second capacitor. The first pole of the fifth fully controllable device is electrically connected to the second terminal of the second capacitor, and the second pole of the fifth fully controllable device is electrically connected to the second pole of the third fully controllable device.

9. A control method for a current source converter, characterized in that, The control method for controlling the current source converter according to any one of claims 1 to 8 includes: The current source converter is started and its auxiliary modules are pre-charged. The operation information of the AC grid for the current source converter is detected, and the operation information indicates whether a fault has occurred in the AC grid; In the event of a fault in the AC power grid, the target auxiliary module in the current source converter is controlled to apply a compensation voltage to the faulty bridge arm, wherein the target auxiliary module is either the first auxiliary module or the second auxiliary module corresponding to the faulty bridge arm.

10. The control method according to claim 9, characterized in that, The auxiliary module of the current source converter includes multiple first auxiliary modules and multiple second auxiliary modules. Each first auxiliary module and each second auxiliary module includes a positive voltage application unit and a negative voltage application unit. The positive voltage application unit includes a first switching unit and a first capacitor connected in series, and the negative voltage application unit includes a second switching unit and the first capacitor connected in series. In the first auxiliary module, the end of the positive voltage application unit near the positive terminal of the first capacitor is electrically connected to a target inductor, the end of the positive voltage application unit near the negative terminal of the first capacitor is electrically connected to the first power device, and the end of the negative voltage application unit near the negative terminal of the first capacitor is electrically connected to the target inductor. One end of the negative voltage application unit near the positive terminal of the first capacitor is electrically connected to the first power device; in the second auxiliary module, one end of the positive voltage application unit near the positive terminal of the first capacitor is electrically connected to the second power device, one end of the positive voltage application unit near the negative terminal of the first capacitor is electrically connected to a target inductor, one end of the negative voltage application unit near the negative terminal of the first capacitor is electrically connected to the second power device, and one end of the negative voltage application unit near the positive terminal of the first capacitor is electrically connected to a target inductor. In the event of a fault in the AC power grid, controlling the target auxiliary module in the current source converter to apply a compensation voltage to the faulty bridge arm includes: The first switching unit of the target auxiliary module of the faulty bridge arm is turned on and the second switching unit is turned off to enable the positive voltage application unit. The first capacitor applies a positive compensation voltage to the faulty bridge arm. The first switching unit of the target auxiliary module of the target commutation bridge arm is turned off and the second switching unit is turned on to enable the negative voltage application unit. The first capacitor applies a negative compensation voltage to the target commutation bridge arm. The positive compensation voltage and the negative compensation voltage form a zero voltage cutoff between the faulty bridge arm and the target commutation bridge arm, thus completing the commutation.

11. The control method according to claim 9, characterized in that, The current source converter includes a first auxiliary module and a second auxiliary module. The first auxiliary module is connected between multiple first power devices and the positive bus of multiple first bridge arms. The second auxiliary module is connected between multiple second power devices and the negative bus of multiple second bridge arms. Both the first and second auxiliary modules include a first sub-auxiliary unit, a second sub-auxiliary unit, a third sub-auxiliary unit, and a second capacitor. The first, second, and third sub-auxiliary units and the second capacitor are connected in parallel. Each first, second, and third sub-auxiliary unit includes a third fully controlled device, a fourth fully controlled device, and a fifth fully controlled device. The second pole of the third fully controllable device in an auxiliary module is electrically connected to the first power device. The first pole of the third fully controllable device is electrically connected to the positive bus and the first pole of the fourth fully controllable device, respectively. The second pole of the third fully controllable device in the second auxiliary module is electrically connected to the negative bus. The first pole of the third fully controllable device is electrically connected to the second power device and the first pole of the fourth fully controllable device, respectively. The second pole of the fourth fully controllable device in both the first and second auxiliary modules is electrically connected to the first terminal of the second capacitor. The first pole of the fifth fully controllable device is electrically connected to the second terminal of the second capacitor. The second pole of the fifth fully controllable device is electrically connected to the second pole of the third fully controllable device. The control method further includes: The third fully controlled device of the target auxiliary module located in the faulty bridge arm is disconnected, and the fourth and fifth fully controlled devices are turned on, so that the second capacitor provides compensation voltage to the faulty bridge arm; Before the faulty bridge arm is restored to conduction, the third fully controlled device and the fourth fully controlled device are controlled to conduct, and the fifth fully controlled device of the adjacent parallel bridge arm is controlled to conduct, so as to discharge the second capacitor.

12. A current source converter system, characterized in that, The device includes a controller and a current source converter as described in any one of claims 1 to 8, wherein the controller is used to execute the control method of the current source converter as described in any one of claims 9 to 11.

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