Hybrid bridge arm and control method thereof, half-bridge circuit and current source type converter

Abstract

The invention relates to a hybrid bridge arm and a control method thereof, a half-bridge circuit and a current source type converter, the half-bridge circuit of the current source type converter comprises an upper bridge arm and a lower bridge arm which are connected in series, at least one of the upper bridge arm and the lower bridge arm is a hybrid bridge arm, the hybrid bridge arm comprises a conduction voltage drop optimization bridge arm and a turn-off current optimization bridge arm which are connected in parallel, the conduction voltage drop of the conduction voltage drop optimization bridge arm is smaller than the conduction voltage drop of the turn-off current optimization bridge arm, and the current turn-off capability of the turn-off current optimization bridge arm is higher than the current turn-off capability of the conduction voltage drop optimization bridge arm. A conduction voltage drop optimization bridge arm with low conduction voltage drop and a turn-off current optimization bridge arm with high current turn-off capacity are connected in parallel to form a mixed bridge arm, and the current source type converter is formed, so that the current turn-off capacity of the current source type converter can be improved while the conduction voltage drop is reduced; the operation efficiency and the operation range of the current source type converter are optimized at the same time, and the working performance constraint upper limit of the current source type converter is improved.

Description

Technical Field

[0001] The present application relates to the technical field of converters, and in particular to a hybrid bridge arm and a control method thereof, a half-bridge circuit and a current source converter. Background Art

[0002] The current source converter is a type of converter that has a high capacity per unit area and can effectively handle DC short-circuit faults without shutting down. It has significant technical advantages in applications such as wind power transmission and offshore wind power networking.

[0003] The topology of the traditional current source converter is a device direct series structure. Among them, the bridge arm is composed of power semiconductor devices directly connected in series. Two groups of bridge arms are connected in series to form a half bridge, and three groups of half bridges are connected in parallel to form the power electronics part of the current source converter. When the switching state of the bridge arm remains unchanged, the injected current generates conduction loss on the conduction voltage drop of the bridge arm; when the switch state of the bridge arm is switched, the device actively shuts down to complete the current transfer. The power semiconductor devices that make up the bridge arm cannot take into account both the shutdown capability and the conduction voltage drop. Therefore, there is a contradiction in the simultaneous optimization of the converter's operating efficiency and operating range, resulting in a constraint upper limit on the operating performance of the traditional current source converter. Summary of the invention

[0004] Based on this, it is necessary to provide a hybrid bridge arm and its control method, a half-bridge circuit and a current source converter that can improve the upper limit of the working performance constraint of the current source converter in order to address the technical problem that the working performance of the traditional current source converter has an upper limit constraint.

[0005] In a first aspect, the present application provides a hybrid bridge arm, which is applied to a current source converter;

[0006] The hybrid bridge arm includes a conduction voltage drop optimized bridge arm and a turn-off current optimized bridge arm in parallel, the conduction voltage drop of the conduction voltage drop optimized bridge arm is smaller than the conduction voltage drop of the turn-off current optimized bridge arm, and the current turn-off capability of the turn-off current optimized bridge arm is higher than the current turn-off capability of the conduction voltage drop optimized bridge arm.

[0007] In one embodiment, the structures of the on-state voltage drop optimization bridge arm and the off-state current optimization bridge arm are different.

[0008] In one of the embodiments, the on-state voltage drop optimization bridge arm and the off-state current optimization bridge arm are both turnable bridge arms.

[0009] In one embodiment, the on-state voltage drop optimized bridge arm includes a first type of reverse resistance fully-controlled power semiconductor device, and the first type of reverse resistance fully-controlled power semiconductor device is a reverse resistance fully-controlled power semiconductor device with a on-state voltage drop less than a preset on-state voltage drop threshold.

[0010] In one of the embodiments, one of the on-state voltage drop optimized bridge arms includes a plurality of the first-type reverse-resistance fully-controlled power semiconductor devices, and each of the first-type reverse-resistance fully-controlled power semiconductor devices is connected in series.

[0011] In one of the embodiments, the on-state voltage drop optimized bridge arm further includes a protection circuit, and the protection circuit is connected in series with the first type of reverse resistance fully controlled power semiconductor device.

[0012] In one embodiment, the shutdown current optimized bridge arm includes a second type of reverse resistance fully controlled power semiconductor device, which is a reverse resistance fully controlled power semiconductor device with a shutdown current greater than a preset shutdown current threshold, or a shutdown loss lower than a preset shutdown loss threshold.

[0013] In one of the embodiments, one of the turn-off current optimization bridge arms includes a plurality of the second-type reverse-resistance fully-controlled power semiconductor devices, and each of the second-type reverse-resistance fully-controlled power semiconductor devices is connected in series.

[0014] In one of the embodiments, the shutdown current optimization bridge arm further includes a protection circuit, and the protection circuit is connected in series with the second type of reverse resistance fully controlled power semiconductor device.

[0015] In one of the embodiments, the hybrid bridge arm further includes a protection circuit, which is connected in series with the parallel on-state voltage drop optimization bridge arm and the off-state current optimization bridge arm.

[0016] In one of the embodiments, the protection circuit is a reactor.

[0017] In one of the embodiments, the hybrid bridge arm further includes a controller, which is connected to the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm and is used to control the on-state of the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm.

[0018] In one of the embodiments, the hybrid bridge arm further includes a series voltage balancing circuit, and the series voltage balancing circuit is connected in parallel with the power semiconductor device in the hybrid bridge arm.

[0019] In one of the embodiments, the series voltage balancing circuit includes a dynamic voltage balancing circuit, a static voltage balancing circuit and a voltage clamping circuit, and the dynamic voltage balancing circuit, the static voltage balancing circuit and the voltage clamping circuit are all connected in parallel with the power semiconductor device.

[0020] In one of the embodiments, the dynamic voltage balancing circuit includes a dynamic voltage balancing resistor and a dynamic voltage balancing capacitor, and a structure formed by the dynamic voltage balancing resistor and the dynamic voltage balancing capacitor being connected in series is connected in parallel with the power semiconductor device.

[0021] In one of the embodiments, the dynamic voltage balancing circuit further includes a diode, and the diode is connected in parallel with the dynamic voltage balancing resistor.

[0022] In one of the embodiments, the hybrid bridge arm further includes a parallel current sharing circuit, which is connected in series with the power semiconductor device in the on-state voltage drop optimization bridge arm or the off-state current optimization bridge arm.

[0023] In one embodiment, the parallel current sharing circuit includes a first winding and a second winding, and the first winding and the second winding are respectively connected in series with power semiconductor devices on different branches in the on-state voltage drop optimization bridge arm; or, the first winding and the second winding are respectively connected in series with power semiconductor devices on different branches in the off-state current optimization bridge arm; the first winding and the second winding are reversely coupled.

[0024] In a second aspect, the present application provides a method for controlling a hybrid bridge arm, the method comprising:

[0025] When the hybrid bridge arm is turned on, the off current is controlled to optimize the bridge arm turning on;

[0026] After the off-current optimization bridge arm is turned on and enters the on state, controlling the on-voltage drop optimization bridge arm to turn on;

[0027] After the on-state voltage drop optimization bridge arm is turned on and enters the on state, controlling the off-state current optimization bridge arm to turn off;

[0028] as well as,

[0029] When the hybrid bridge arm is turned off, controlling the turn-off current to optimize the bridge arm opening;

[0030] Controlling the conduction voltage drop to optimize the bridge arm shutdown;

[0031] After the on-state voltage drop optimization bridge arm is turned off, the off-state current optimization bridge arm is controlled to be turned off.

[0032] In one embodiment, the method further comprises:

[0033] When the hybrid bridge arm is turned on, controlling the off current to optimize the bridge arm to turn on;

[0034] After the off-current optimized bridge arm is turned on and enters the on-state, the on-voltage drop optimized bridge arm is controlled to be turned on, and the off-current optimized bridge arm and the on-voltage drop optimized bridge arm are simultaneously conducting current;

[0035] as well as,

[0036] When the hybrid bridge arm is turned off, controlling the conduction voltage drop to optimize the bridge arm turn off;

[0037] After the on-state voltage drop optimization bridge arm is turned off, the off-state current optimization bridge arm is controlled to be turned off.

[0038] In one embodiment, the method further comprises:

[0039] When the hybrid bridge arm is turned on, controlling the conduction voltage drop optimization bridge arm to turn on;

[0040] as well as,

[0041] When the hybrid bridge arm is turned off, controlling the turn-off current to optimize the bridge arm opening;

[0042] After the off-current optimization bridge arm is turned on and enters the on state, controlling the on-voltage drop optimization bridge arm to turn off;

[0043] After the on-state voltage drop optimization bridge arm is turned off, the off-state current optimization bridge arm is controlled to be turned off.

[0044] In one embodiment, the method further comprises:

[0045] When the hybrid bridge arm is turned on, controlling the conduction voltage drop optimization bridge arm to turn on;

[0046] After the on-state voltage drop optimization bridge arm is turned on and enters the on state, the off-state current optimization bridge arm is controlled to be turned on, and the off-state current optimization bridge arm and the on-state voltage drop optimization bridge arm are simultaneously conducting current;

[0047] as well as,

[0048] When the hybrid bridge arm is turned off, controlling the conduction voltage drop to optimize the bridge arm turn off;

[0049] After the on-state voltage drop optimization bridge arm is turned off, the off-state current optimization bridge arm is controlled to be turned off.

[0050] In a third aspect, the present application provides a half-bridge circuit, comprising an upper bridge arm and a lower bridge arm connected in series, wherein at least one of the upper bridge arm and the lower bridge arm is a hybrid bridge arm as described above.

[0051] In a fourth aspect, the present application provides a current source converter, comprising the half-bridge circuit as described above.

[0052] The above-mentioned hybrid bridge arm and its control method, half-bridge circuit and current source converter, the hybrid bridge arm of the current source converter includes a parallel on-voltage drop optimized bridge arm and a turn-off current optimized bridge arm, the on-voltage drop of the on-voltage drop optimized bridge arm is less than the on-voltage drop of the turn-off current optimized bridge arm, and the current turn-off capability of the turn-off current optimized bridge arm is higher than the current turn-off capability of the on-voltage drop optimized bridge arm. There are differences in the advantageous performance parameters of the on-voltage drop optimized bridge arm and the turn-off current optimized bridge arm. A hybrid bridge arm is formed by connecting an on-voltage drop optimized bridge arm with a low on-voltage drop and a turn-off current optimized bridge arm with a high current turn-off capability in parallel. The hybrid bridge arm, as a component of the current source converter, enables the current source converter to improve its current turn-off capability while reducing the on-voltage drop, thereby achieving simultaneous optimization of the operating efficiency and operating range of the current source converter, and improving the upper limit of the operating performance constraint of the current source converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0054] Figure 1 is a schematic structural diagram of a current source converter in one embodiment;

[0055] Figure 2 is a schematic structural diagram of a half-bridge circuit of a current source converter in one embodiment;

[0056] Figure 3 A schematic diagram of the structure of a bridge arm with optimized on-state voltage drop in one embodiment;

[0057] Figure 4 A schematic diagram of the structure of a shutdown current optimization bridge arm in one embodiment;

[0058] Figure 5 is a schematic structural diagram of a half-bridge circuit of a current source converter in another embodiment;

[0059] Figure 6 It is a structural schematic diagram of a bridge arm with optimized on-state voltage drop in another embodiment;

[0060] Figure 7 A schematic diagram of the structure of a shutdown current optimization bridge arm in another embodiment;

[0061] Figure 8 is a schematic diagram of the structure of a protection circuit in one embodiment;

[0062] Fig. 9A schematic diagram of a partial structure of a hybrid bridge arm in one embodiment;

[0063] Fig.10 A schematic diagram of a partial structure of a hybrid bridge arm in another embodiment;

[0064] Fig.11 FIG. 4 is a schematic diagram of a partial structure of a hybrid bridge arm in yet another embodiment. DETAILED DESCRIPTION

[0065] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0067] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0068] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0069] It can be understood that “at least one” means one or more, “plurality” means two or more, and “at least a portion of an element” means a part or all of an element.

[0070] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0071] The hybrid bridge arm 1 provided in the embodiment of the present application is a component of a current source converter. For example, two hybrid bridge arms connected in series can form a half-bridge circuit. Alternatively, the hybrid bridge arm and the diode bridge arm can also form a half-bridge circuit. The half-bridge circuit is a component of a current source converter. For example, Figure 1 As shown, there are three half-bridge circuits 2, which are connected in parallel to form the power electronic part of the current source converter. The two ends of each half-bridge circuit 2 are connected to the DC port 4 through a smoothing reactor 3, and the midpoint of each half-bridge circuit 2 is connected to the AC port 6 through an LC filter 5.

[0072] Specifically, in one embodiment, the half-bridge circuit 2 of the current source converter includes an upper bridge arm and a lower bridge arm connected in series, and at least one of the upper bridge arm and the lower bridge arm is a hybrid bridge arm 1. That is, Figure 2 As shown, both the upper bridge arm and the lower bridge arm are hybrid bridge arm 1; or, the upper bridge arm is hybrid bridge arm 1 and the lower bridge arm is non-hybrid bridge arm; or, the upper bridge arm is non-hybrid bridge arm and the lower bridge arm is hybrid bridge arm 1. The common end of the upper bridge arm and the lower bridge arm is used as the midpoint of the half-bridge circuit 2 and is connected to the AC port 6 through the LC filter 5.

[0073] When the current source converter is operating in a steady state, the current amplitude of the smoothing reactor 3 is approximately constant. When the upper bridge arm of the half-bridge circuit 2 is turned on and the lower bridge arm is blocked, a positive current is injected into the corresponding phase AC port 6, and the current amplitude is the same as that of the smoothing reactor 3; when the lower bridge arm of the half-bridge circuit 2 is turned on and the upper bridge arm is blocked, a negative current is injected into the corresponding phase AC port 6, and the current amplitude is the same as that of the smoothing reactor 3; when the upper and lower bridge arms of the half-bridge circuit 2 are turned on at the same time, the smoothing reactor 3 continues the current through the short-circuited half-bridge circuit 2, and the current amplitude injected into the corresponding phase AC port 6 is zero.

[0074] When the switch states of the upper and lower arms remain unchanged, the injected current generates conduction loss on the conduction voltage drop of the upper and lower arms; when the switch states of the upper and lower arms are switched, the device actively shuts down to complete the current transfer. Therefore, the conduction voltage drop and shutdown capability of the upper and lower arms are key parameters. A lower conduction voltage drop can improve the efficiency of the current source converter, reduce the heat dissipation power requirement and operating cost; a higher shutdown capability can expand the operating range of the current source converter, improve fault resistance and operating reliability. The upper and lower arms have four states, namely, on, off, conduction and blocking, among which on and off are transient processes, and on and blocking are stable states. Switching from conduction to blocking is off, and switching from blocking to conduction is on.

[0075] like Figure 2As shown, the hybrid bridge arm 1 includes a conduction voltage drop optimized bridge arm 11 and a turn-off current optimized bridge arm 12 in parallel, the conduction voltage drop of the conduction voltage drop optimized bridge arm 11 is less than the conduction voltage drop of the turn-off current optimized bridge arm 12, and the current turn-off capability of the turn-off current optimized bridge arm 12 is higher than the current turn-off capability of the conduction voltage drop optimized bridge arm 11. Specifically, the advantageous performance parameters of the conduction voltage drop optimized bridge arm 11 and the turn-off current optimized bridge arm 12 can be different by setting different structures for the conduction voltage drop optimized bridge arm 11 and the turn-off current optimized bridge arm 12. The advantageous performance parameter of the conduction voltage drop optimized bridge arm 11 is the conduction voltage drop, and the advantageous performance parameter of the turn-off current optimized bridge arm 12 is the current turn-off capability. The current turn-off capability can be reflected by different parameters, such as the turn-off current, turn-off loss or turn-off speed, and a high current turn-off capability can be reflected by a large turn-off current, a low turn-off loss or a fast turn-off speed.

[0076] Exemplarily, one working mode of the hybrid bridge arm 1 is as follows: when the hybrid bridge arm 1 is turned on, the off-current optimized bridge arm 12 is first triggered to turn on, and the current rise slope is controlled, thereby reducing the converter's requirements for the current rise rate protection circuit. After the off-current optimized bridge arm 12 is turned on and enters the on-state, the voltage across the hybrid bridge arm 1 is clamped close to zero, and at this time the on-voltage drop optimized bridge arm 11 is triggered to turn on, and the on-voltage drop optimized bridge arm 11 achieves zero-voltage soft turn-on, reduces turn-on loss, and begins to shunt with the off-current optimized bridge arm 12. Since the on-impedance of the on-voltage drop optimized bridge arm 11 is lower, the current flowing through the on-voltage drop optimized bridge arm 11 is greater than that of the off-current optimized bridge arm 12; after the on-voltage drop optimized bridge arm 11 is turned on and enters the on-state, the off-current optimized bridge arm 12 is triggered to turn off, and the off-current optimized bridge arm 12 achieves zero-voltage soft turn-off, reduces turn-off loss, and transfers all current to the on-state The voltage drop optimizes the bridge arm 11, reduces the bridge arm conduction loss and improves the converter operation efficiency; when the hybrid bridge arm 1 is turned off, the off-current optimized bridge arm 12 is first triggered to turn on, and the off-current optimized bridge arm 12 completes the zero-voltage soft turn-on and begins to shunt with the on-voltage drop optimized bridge arm 11; then the on-voltage drop optimized bridge arm 11 is triggered to turn off, and after the on-voltage drop optimized bridge arm 11 completes the zero-voltage soft turn-off, the current of all the hybrid bridge arms 1 is transferred to the off-current optimized bridge arm 12; finally, the off-current optimized bridge arm 12 is triggered to turn off, and its large current shut-off capability is used to improve the converter operation range, and the off-current optimized bridge arm 12 has a short current conduction time, which reduces the current level requirements for the component devices.

[0077] This method utilizes the controllable rise rate of the on-current of the off-current optimization bridge arm 12 to simplify the protection circuit or even completely remove it. This method can also reduce the flow time of the off-current optimization bridge arm 12 and the current level requirements of the component devices.

[0078] In this embodiment, the hybrid bridge arm 1 includes a parallel on-voltage drop optimized bridge arm 11 and a turn-off current optimized bridge arm 12, the on-voltage drop of the on-voltage drop optimized bridge arm 11 is less than the on-voltage drop of the turn-off current optimized bridge arm 12, and the current turn-off capability of the turn-off current optimized bridge arm 12 is higher than the current turn-off capability of the on-voltage drop optimized bridge arm 11. There are differences in the advantageous performance parameters of the on-voltage drop optimized bridge arm 11 and the turn-off current optimized bridge arm 12. The hybrid bridge arm 1 is formed by connecting the on-voltage drop optimized bridge arm 11 with low on-voltage drop and the turn-off current optimized bridge arm 12 with high current turn-off capability in parallel, and the hybrid bridge arm 1 forms a half-bridge circuit 2, and the half-bridge circuit 2 constitutes a current source converter, so that the current source converter can improve its current turn-off capability while reducing the on-voltage drop, thereby achieving simultaneous optimization of the operating efficiency and operating range of the current source converter, and improving the upper limit of the working performance constraint of the current source converter.

[0079] In one embodiment, the structures of the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 are different. Specifically, the different structures of the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 may be that the number of devices included in the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 is different, or the types of devices included in the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 are different. The different structures of the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 may make the performance parameters of the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 different, satisfying the requirements that the on-state voltage drop of the on-state voltage drop optimized bridge arm 11 is less than the on-state voltage drop of the off-state current optimized bridge arm 12, and the current shutoff capability of the off-state current optimized bridge arm 12 is higher than the current shutoff capability of the on-state voltage drop optimized bridge arm 11.

[0080] In this embodiment, the structures of the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 are different, so that the performance parameters of the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 can be different, meeting the requirements that the on-state voltage drop of the on-state voltage drop optimized bridge arm 11 is smaller than the on-state voltage drop of the off-state current optimized bridge arm 12, and the current shutoff capability of the off-state current optimized bridge arm 12 is higher than the current shutoff capability of the on-state voltage drop optimized bridge arm 11.

[0081] In one embodiment, both the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 are turnable bridge arms. The on-state voltage drop optimized bridge arm 11 is a turnable bridge arm, which means that the device included in the on-state voltage drop optimized bridge arm 11 is a turnable device, for example, a turnable power semiconductor device. The off-state current optimized bridge arm 12 is a turnable bridge arm, which means that the device included in the off-state current optimized bridge arm 12 is a turnable device, for example, a turnable power semiconductor device.

[0082] In this embodiment, both the on-voltage drop optimization bridge arm 11 and the off-current optimization bridge arm 12 are turnable bridge arms, which can enrich the working mode of the hybrid bridge arm 1, thereby optimizing the working performance of the current source converter.

[0083] The structure of the on-state voltage drop optimized bridge arm 11 is not unique. In one embodiment, the on-state voltage drop optimized bridge arm 11 includes a first type of reverse resistance fully-controlled power semiconductor device, which is a reverse resistance fully-controlled power semiconductor device with a on-state voltage drop less than a preset on-state voltage drop threshold.

[0084] Specifically, the specific value of the preset on-state voltage drop threshold is not limited, as long as the technicians in this field believe that it can meet the relevant requirements. When the on-state voltage drop is less than the preset on-state voltage drop threshold, it means that the on-state voltage is reduced. The on-state voltage drop optimization bridge arm 11 includes a first type of reverse resistance fully controlled power semiconductor device with reduced on-state voltage, so that the on-state voltage of the on-state voltage drop optimization bridge arm 11 is reduced. Among them, the type of the first type of reverse resistance fully controlled power semiconductor device is not unique, including but not limited to reverse resistance IGCT (Integrated Gate-Commutated Thyristor, integrated gate commutated thyristor), reverse conduction or asymmetric IGCT series diode, etc.

[0085] In this embodiment, the on-state voltage drop optimized bridge arm 11 includes a first type of reverse resistance fully-controlled power semiconductor device, which is a reverse resistance fully-controlled power semiconductor device with a on-state voltage drop less than a preset on-state voltage drop threshold, and can reduce the on-state voltage drop of the on-state voltage drop optimized bridge arm 11.

[0086] Furthermore, in one embodiment, a conduction voltage drop optimized bridge arm 11 includes a plurality of first-class reverse resistance fully-controlled power semiconductor devices, and each first-class reverse resistance fully-controlled power semiconductor device is connected in series. Among them, the plurality can be two, three or more, which can be determined according to actual needs. The series connection of a plurality of first-class reverse resistance fully-controlled power semiconductor devices can improve the operating voltage and power capacity of the current source converter. It can be understood that in other embodiments, a conduction voltage drop optimized bridge arm 11 may also include only one first-class reverse resistance fully-controlled power semiconductor device. This structure can avoid the problem of difficulty in implementing the current source converter caused by the direct series connection of devices.

[0087] In this embodiment, a conduction voltage drop optimized bridge arm 11 includes multiple first-type reverse resistance fully-controlled power semiconductor devices. Each first-type reverse resistance fully-controlled power semiconductor device is connected in series, which can increase the operating voltage and power capacity of the current source converter and improve the operating performance of the current source converter.

[0088] In one embodiment, Figure 3As shown, the on-state voltage drop optimized bridge arm 11 further includes a protection circuit 112 , and the protection circuit 112 is connected in series with the first type reverse resistance fully controlled power semiconductor device 111 .

[0089] Specifically, the protection circuit can play a protective role. Exemplarily, the protection circuit can be a current rise rate protection circuit, which is connected in series with the first type of reverse resistance fully controlled power semiconductor device, and can limit the current rise slope of the conduction voltage drop optimization bridge arm 11, thereby protecting the conduction voltage drop optimization bridge arm 11. The type of protection circuit is not unique, for example, it can include inductive devices, such as reactors, controllable saturated reactors, etc.

[0090] In this embodiment, the on-state voltage drop optimized bridge arm 11 also includes a protection circuit, which is connected in series with the first type of reverse resistance fully controlled power semiconductor device, and can limit the current rising slope of the on-state voltage drop optimized bridge arm 11, thereby protecting the on-state voltage drop optimized bridge arm 11.

[0091] The structure of the turn-off current optimization bridge arm 12 is not unique. Exemplarily, in one embodiment, the turn-off current optimization bridge arm 12 includes a second type of reverse resistance fully controlled power semiconductor device, which is a reverse resistance fully controlled power semiconductor device with a turn-off current greater than a preset turn-off current threshold, or a turn-off loss lower than a preset turn-off loss threshold.

[0092] Specifically, the specific values ​​of the preset turn-off current threshold and the preset turn-off loss threshold are not limited, as long as the technicians in this field believe that they can meet the relevant requirements. When the turn-off current is greater than the preset turn-off current threshold, it means that the turn-off current is large. The turn-off loss is lower than the preset turn-off loss threshold, which means that the turn-off loss is low. When the turn-off current is large or the turn-off loss is low, it means that the turn-off capability is strong. The turn-off current optimization bridge arm 12 includes a second type of reverse resistance fully controlled power semiconductor device with high turn-off capability, so that the turn-off capability of the turn-off current optimization bridge arm 12 is strong. Among them, the type of the second type of reverse resistance fully controlled power semiconductor device is not unique, including but not limited to reverse resistance IGBT (Insulated Gate Bipolar Transistor, insulated gate bipolar transistor), asymmetric IGBT series diode, MOSFET series diode, emitter turn-off thyristor series diode and diode assisted turn-off thyristor, etc.

[0093] In this embodiment, the shutdown current optimized bridge arm 12 includes a second type of reverse resistance fully controlled power semiconductor device, which is a reverse resistance fully controlled power semiconductor device with a shutdown current greater than a preset shutdown current threshold, or a shutdown loss lower than a preset shutdown loss threshold, which can make the shutdown capability of the shutdown current optimized bridge arm 12 strong.

[0094] Furthermore, in one embodiment, a turn-off current optimization bridge arm 12 includes a plurality of second-type reverse-resistance fully-controlled power semiconductor devices, and each of the second-type reverse-resistance fully-controlled power semiconductor devices is connected in series.

[0095] Among them, the plurality of may be two, three or more, which can be determined according to actual needs. A plurality of second-type reverse resistance fully controlled power semiconductor devices are connected in series to improve the operating voltage and power capacity of the current source converter. It can be understood that in other embodiments, a turn-off current optimization bridge arm 12 may also include only one turn-off current optimization bridge arm 12 reverse resistance fully controlled power semiconductor device, and this structure can avoid the problem of difficulty in implementing the current source converter caused by the direct series connection of devices.

[0096] In this embodiment, a turn-off current optimization bridge arm 12 includes multiple second-type reverse resistance fully-controlled power semiconductor devices, and each second-type reverse resistance fully-controlled power semiconductor device is connected in series, which can increase the operating voltage and power capacity of the current source converter and improve the operating performance of the current source converter.

[0097] In one embodiment, Figure 4 As shown, the turn-off current optimization bridge arm 12 further includes a protection circuit 122 , and the protection circuit 122 is connected in series with the second type reverse resistance fully controlled power semiconductor device 121 .

[0098] Specifically, the protection circuit can play a protective role. Exemplarily, the protection circuit can be a current rise rate protection circuit, which is connected in series with the second type of reverse resistance fully controlled power semiconductor device, and can limit the current rise slope of the turn-off current optimization bridge arm 12, thereby protecting the turn-off current optimization bridge arm 12. The type of protection circuit is not unique, for example, it can include inductive devices such as reactors, controllable saturated reactors, etc. It can be understood that when the turn-off current optimization bridge arm 12 includes a protection circuit, the on-state voltage drop optimization bridge arm 11 may include a protection circuit, or may not include a protection circuit.

[0099] In this embodiment, the shutdown current optimization bridge arm 12 also includes a protection circuit, which is connected in series with the second type of reverse resistance fully controlled power semiconductor device, and can limit the current rising slope of the shutdown current optimization bridge arm 12, thereby protecting the shutdown current optimization bridge arm 12.

[0100] In one embodiment, the half-bridge circuit 2 of the current source converter further includes a protection circuit, which is connected in series with the parallel on-voltage drop optimized bridge arm 11 and the off-current optimized bridge arm 12. Specifically, after the on-voltage drop optimized bridge arm 11 and the off-current optimized bridge arm 12 are connected in parallel, the parallel structure formed is connected in series with the protection circuit. The current rising slope of the on-voltage drop optimized bridge arm 11 and the off-current optimized bridge arm 12 can be limited to protect the on-voltage drop optimized bridge arm 11 and the off-current optimized bridge arm 12. The type of protection circuit is not unique, for example, it can include inductive devices such as reactors, controllable saturated reactors, etc. It can be understood that when the parallel structure formed by the on-voltage drop optimized bridge arm 11 and the off-current optimized bridge arm 12 in parallel is connected to the protection circuit, the off-current optimized bridge arm 12 may include a protection circuit or not, and the on-voltage drop optimized bridge arm 11 may also include a protection circuit or not, which can be determined according to actual needs.

[0101] In this embodiment, Figure 5 As shown, the half-bridge circuit 2 of the current source converter also includes a protection circuit 13, which is connected in series with the parallel on-voltage drop optimized bridge arm 11 and the off-current optimized bridge arm 12, and can limit the current rising slope of the on-voltage drop optimized bridge arm 11 and the off-current optimized bridge arm 12, thereby protecting the on-voltage drop optimized bridge arm 11 and the off-current optimized bridge arm 12, which is beneficial to improving the working performance of the half-bridge circuit 2.

[0102] Furthermore, the type of the protection circuit is not limited. In one embodiment, the protection circuit is a reactor. The reactor can limit the speed of the current rise when the current in the circuit rises, thereby limiting the current rise slope. It is understood that in other embodiments, the structure and type of the protection circuit can also be other, as long as those skilled in the art believe that it can be implemented.

[0103] In one embodiment, the half-bridge circuit 2 of the current source converter further includes a series voltage balancing circuit, which is connected in parallel with the power semiconductor device in the hybrid bridge arm 1 .

[0104] Specifically, the series voltage balancing circuit is connected in parallel with the power semiconductor device in the hybrid bridge arm 1, which means that the series voltage balancing circuit can be connected in parallel with the power semiconductor device in the on-state voltage drop optimized bridge arm 11, and / or the series voltage balancing circuit can be connected in parallel with the power semiconductor device in the off-state current optimized bridge arm 12. Further, when the on-state voltage drop optimized bridge arm 11 includes a first type of reverse resistance fully controlled power semiconductor device, and the off-state current optimized bridge arm 12 includes a second type of reverse resistance fully controlled power semiconductor device, the series voltage balancing circuit can be connected in parallel with the first type of reverse resistance fully controlled power semiconductor device in the on-state voltage drop optimized bridge arm 11, and / or the series voltage balancing circuit can be connected in parallel with the second type of reverse resistance fully controlled power semiconductor device in the off-state current optimized bridge arm 12.

[0105] Depending on the structure of the series voltage balancing circuit, the function of the series voltage balancing circuit is different. For example, when the series voltage balancing circuit includes a dynamic voltage balancing circuit, the dynamic voltage balancing circuit can slow down the rate of change of the voltage across the power semiconductor device when the power semiconductor device in the connected on-state voltage drop optimization bridge arm 11 and the power semiconductor device in the off-state current optimization bridge arm 12 are in the on and off transient state, thereby reducing the dynamic voltage difference between the devices. It can be understood that in other embodiments, the series voltage balancing circuit can also include other structures, as long as those skilled in the art believe that it can be implemented.

[0106] In this embodiment, the half-bridge circuit 2 of the current source converter further includes a series voltage balancing circuit, which is connected in parallel with the power semiconductor device in the hybrid bridge arm 1 to achieve voltage balancing and improve circuit stability.

[0107] The structure of the series voltage balancing circuit is not unique. For example, in one embodiment, the series voltage balancing circuit includes a dynamic voltage balancing circuit, a static voltage balancing circuit and a voltage clamping circuit, and the dynamic voltage balancing circuit, the static voltage balancing circuit and the voltage clamping circuit are all connected in parallel with the power semiconductor device.

[0108] Specifically, the dynamic voltage balancing circuit is connected in parallel with the power semiconductor device, which means that the dynamic voltage balancing circuit can be connected in parallel with the power semiconductor device in the on-state voltage drop optimized bridge arm 11, and / or the dynamic voltage balancing circuit can be connected in parallel with the power semiconductor device in the off-state current optimized bridge arm 12. Further, when the on-state voltage drop optimized bridge arm 11 includes a first type of reverse resistance fully controlled power semiconductor device, and the off-state current optimized bridge arm 12 includes a second type of reverse resistance fully controlled power semiconductor device, the dynamic voltage balancing circuit can be connected in parallel with the first type of reverse resistance fully controlled power semiconductor device in the on-state voltage drop optimized bridge arm 11, and / or the dynamic voltage balancing circuit can be connected in parallel with the second type of reverse resistance fully controlled power semiconductor device in the off-state current optimized bridge arm 12. The dynamic voltage balancing circuit can slow down the rate of change of the voltage across the power semiconductor device when the power semiconductor device in the connected on-state voltage drop optimized bridge arm 11 and the power semiconductor device in the off-state current optimized bridge arm 12 are in the turn-on and turn-off transient states, thereby reducing the dynamic voltage difference between the devices.

[0109] The static voltage balancing circuit is connected in parallel with the power semiconductor device, which means that the static voltage balancing circuit can be connected in parallel with the power semiconductor device in the on-state voltage drop optimized bridge arm 11, and / or the static voltage balancing circuit can be connected in parallel with the power semiconductor device in the off-state current optimized bridge arm 12. Furthermore, when the on-state voltage drop optimized bridge arm 11 includes a first type of reverse resistance fully controlled power semiconductor device, and the off-state current optimized bridge arm 12 includes a second type of reverse resistance fully controlled power semiconductor device, the static voltage balancing circuit can be connected in parallel with the first type of reverse resistance fully controlled power semiconductor device in the on-state voltage drop optimized bridge arm 11, and / or the static voltage balancing circuit can be connected in parallel with the second type of reverse resistance fully controlled power semiconductor device in the off-state current optimized bridge arm 12. The static voltage balancing circuit can balance the leakage current of the power semiconductor device when the connected power semiconductor device is in a blocking state, thereby reducing the static voltage difference between the devices, which is beneficial to improving the working performance of the power semiconductor device.

[0110] The voltage clamping circuit is connected in parallel with the power semiconductor device, which means that the voltage clamping circuit can be connected in parallel with the power semiconductor device in the on-state voltage drop optimized bridge arm 11, and / or the voltage clamping circuit can be connected in parallel with the power semiconductor device in the off-state current optimized bridge arm 12. Further, when the on-state voltage drop optimized bridge arm 11 includes a first type of reverse resistance fully controlled power semiconductor device, and the off-state current optimized bridge arm 12 includes a second type of reverse resistance fully controlled power semiconductor device, the voltage clamping circuit can be connected in parallel with the first type of reverse resistance fully controlled power semiconductor device in the on-state voltage drop optimized bridge arm 11, and / or the voltage clamping circuit can be connected in parallel with the second type of reverse resistance fully controlled power semiconductor device in the off-state current optimized bridge arm 12. The voltage clamping circuit can limit the voltage of the parallel branch to near the action threshold, and realize dynamic voltage equalization under extreme working conditions.

[0111] In this embodiment, the series voltage balancing circuit includes a dynamic voltage balancing circuit, a static voltage balancing circuit and a voltage clamping circuit, and the dynamic voltage balancing circuit, the static voltage balancing circuit and the voltage clamping circuit are all connected in parallel with the power semiconductor device. The dynamic voltage balancing circuit can slow down the rate of change of the voltage across the power semiconductor device when the power semiconductor device in the connected on-voltage drop optimization bridge arm 11 and the power semiconductor device in the off-current optimization bridge arm 12 are in the turn-on and turn-off transient states, thereby reducing the dynamic voltage difference between the devices. The static voltage balancing circuit can balance the leakage current of the power semiconductor device when the connected power semiconductor device is in a blocked state, thereby reducing the static voltage difference between the devices, which is beneficial to improving the working performance of the power semiconductor device. The voltage clamping circuit can limit the voltage of the parallel branch to near the action threshold to achieve dynamic voltage balancing under extreme working conditions.

[0112] There are also multiple options for the structure of the dynamic voltage balancing circuit. For example, in one embodiment, the dynamic voltage balancing circuit includes a dynamic voltage balancing resistor and a dynamic voltage balancing capacitor. The structure formed by the dynamic voltage balancing resistor and the dynamic voltage balancing capacitor connected in series is connected in parallel with the power semiconductor device.

[0113] Specifically, when the power semiconductor device connected to the dynamic voltage balancing circuit is in a shutdown transient state, the voltage at both ends rises and charges the dynamic voltage balancing capacitor through the dynamic voltage balancing resistor. The dynamic voltage balancing circuit provides an additional current path to reduce the equivalent input impedance at both ends of the power semiconductor device and the rate of rise of the voltage at both ends. When the power semiconductor device connected to the dynamic voltage balancing circuit is in a turn-on transient state, the voltage at both ends drops and discharges the dynamic voltage balancing capacitor through the dynamic voltage balancing resistor. The dynamic voltage balancing circuit provides an additional current source to reduce the equivalent output impedance at both ends of the power semiconductor device and the rate of drop of the voltage at both ends.

[0114] In this embodiment, the dynamic voltage equalizing circuit includes a dynamic voltage equalizing resistor and a dynamic voltage equalizing capacitor. The structure formed by the dynamic voltage equalizing resistor and the dynamic voltage equalizing capacitor in series is connected in parallel with the power semiconductor device. When the connected power semiconductor device is in a shutdown or turn-on transient state, the dynamic voltage equalizing resistor and the dynamic voltage equalizing capacitor charge or discharge the dynamic voltage equalizing capacitor through the dynamic voltage equalizing resistor. The dynamic voltage equalizing circuit provides an additional current source to reduce the equivalent output impedance at both ends of the power semiconductor device and the rate of change of the voltage at both ends.

[0115] In one embodiment, the dynamic voltage balancing circuit further includes a diode, which is connected in parallel with the dynamic voltage balancing resistor.

[0116] Specifically, when the anode port voltage of the power semiconductor device connected to the dynamic voltage equalization circuit rises positively relative to the cathode port, the electromotive force charges the dynamic voltage equalization capacitor through the diode, and the dynamic voltage equalization resistor is bypassed and no voltage drop is generated, thereby giving full play to the fast voltage equalization effect of the dynamic voltage equalization capacitor on voltages with high rise rates.

[0117] When the voltage at the anode port of the power semiconductor device connected to the dynamic voltage balancing circuit drops from a high potential relative to the cathode port, the electromotive force is discharged to the dynamic voltage balancing capacitor through the dynamic voltage balancing resistor, thereby achieving dynamic voltage balancing by slowing down the voltage drop rate.

[0118] In this embodiment, the dynamic voltage balancing circuit further includes a diode, which is connected in parallel with the dynamic voltage balancing resistor, thereby improving the voltage balancing and limiting effects under high-rise-rate voltage change conditions.

[0119] In one embodiment, the half-bridge circuit 2 of the current source converter also includes a parallel current balancing circuit, and the parallel current balancing circuit is connected in series with the power semiconductor device in the on-state voltage drop optimized bridge arm or the off-state current optimized bridge arm. The parallel current balancing circuit can be connected in series with the power semiconductor device in the on-state voltage drop optimized bridge arm to expand the upper current limit of the on-state voltage drop optimized bridge arm. Alternatively, the parallel current balancing circuit can be connected in series with the power semiconductor device in the off-state current optimized bridge arm to expand the upper current limit of the off-state current optimized bridge arm. That is, in a hybrid bridge arm, one of the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm can be connected in series with a parallel current balancing circuit, or both the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm can be connected in series with a parallel current balancing circuit, which is determined according to specific needs.

[0120] In this embodiment, the half-bridge circuit 2 of the current source converter also includes a parallel current balancing circuit, which is connected in series with the power semiconductor device in the on-state voltage drop optimization bridge arm or the off-state current optimization bridge arm. The parallel current balancing circuit can expand the current upper limit of the connected on-state voltage drop optimization bridge arm or the off-state current optimization bridge arm, and realize the current dynamic balance of the power semiconductor device in the connected on-state voltage drop optimization bridge arm or the off-state current optimization bridge arm during the turn-on process and the on-state.

[0121] The structure of the parallel current balancing circuit is not limited. For example, in one embodiment, the parallel current balancing circuit includes a first winding and a second winding, and the first winding and the second winding are respectively connected in series with power semiconductor devices on different branches in the on-state voltage drop optimization bridge arm. Alternatively, the first winding and the second winding are respectively connected in series with power semiconductor devices on different branches in the off-state current optimization bridge arm; the first winding and the second winding are reversely coupled.

[0122] Specifically, the first winding and the second winding are respectively connected in series with power semiconductor devices on different branches in the conduction voltage drop optimization bridge arm. The conduction voltage drop optimization bridge arm may include multiple parallel sub-bridge arms, each of which has a power semiconductor device. The first winding and the second winding are respectively connected in series with power semiconductor devices on different branches in the conduction voltage drop optimization bridge arm. Taking the conduction voltage drop optimization bridge arm as an example, the sub-bridge arms included in the bridge arm are the first sub-bridge arm and the second sub-bridge arm. The first sub-bridge arm and the second sub-bridge arm are connected in parallel, and the first sub-bridge arm and the second sub-bridge arm both include power semiconductor devices. Then, the first winding is connected in series with the power semiconductor device in the first sub-bridge arm, and the second winding is connected in series with the power semiconductor device in the second sub-bridge arm. When the power semiconductor device connected in series with the first winding is turned on faster, a reverse electromotive force will be generated on the second winding. The electromotive force strengthens the positive effect of the voltage at both ends of the bridge arm sub-unit composed of the parallel current sharing circuit and the conduction voltage drop optimized bridge arm on the current rise rate of the power semiconductor device connected in series with the second winding, and vice versa, ultimately achieving a dynamic balance of current in the turn-on process and conduction state of the two groups of power semiconductor devices in the two sub-bridge arms in the conduction voltage drop optimized bridge arm.

[0123] Alternatively, the first winding and the second winding are respectively connected in series with power semiconductor devices on different branches in the off-current optimization bridge arm. The off-current optimization bridge arm may include multiple parallel sub-bridge arms, each of which has a power semiconductor device. The first winding and the second winding are respectively connected in series with power semiconductor devices on different branches in the off-current optimization bridge arm. Taking the off-current optimization bridge arm as an example, the sub-bridge arms included in the bridge arm are the first sub-bridge arm and the second sub-bridge arm. The first sub-bridge arm and the second sub-bridge arm are connected in parallel, and the first sub-bridge arm and the second sub-bridge arm both include power semiconductor devices. Then, the first winding is connected in series with the power semiconductor device in the first sub-bridge arm, and the second winding is connected in series with the power semiconductor device in the second sub-bridge arm. When the power semiconductor device connected in series with the first winding is turned on faster, a reverse electromotive force will be generated on the second winding. The electromotive force strengthens the positive effect of the voltage at both ends of the bridge arm sub-unit composed of the parallel current sharing circuit and the shutdown current optimization bridge arm on the current rise rate of the power semiconductor device connected in series with the second winding, and vice versa, ultimately achieving a dynamic balance of current in the turn-on process and conduction state of the two groups of power semiconductor devices in the two sub-bridge arms in the shutdown current optimization bridge arm.

[0124] In this embodiment, the parallel current sharing circuit includes a first winding and a second winding, and the first winding and the second winding are respectively connected in series with power semiconductor devices on different branches in the on-state voltage drop optimization bridge arm. Alternatively, the first winding and the second winding are respectively connected in series with power semiconductor devices on different branches in the off-state current optimization bridge arm; the first winding and the second winding are reversely coupled. The first winding and the second winding can make the current shared by different branches in the on-state voltage drop optimization bridge arm basically the same, or make the current shared by different branches in the off-state current optimization bridge arm basically the same, so as to realize parallel current sharing between homogeneous sub-bridge arms. Among them, homogeneous sub-bridge arms are different sub-bridge arms in the same on-state voltage drop optimization bridge arm, or different sub-bridge arms in the same off-state current optimization bridge arm.

[0125] In one embodiment, the hybrid bridge arm further includes a controller, which is connected to the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm and is used to control the on-state of the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm.

[0126] The conduction state includes four states: on, off, conduction and blocking. Further, on and off are transient processes, and on and blocking are stable states. Switching from on to blocking is off, and switching from blocking to on is on.

[0127] Specifically, the controller can be connected to the first type of reverse resistance fully controlled power semiconductor device in the on-state voltage drop optimized bridge arm to control the on-state of the first type of reverse resistance fully controlled power semiconductor device. The controller can also be connected to the second type of reverse resistance fully controlled power semiconductor device in the off-state current optimized bridge arm to control the on-state of the second type of reverse resistance fully controlled power semiconductor device.

[0128] In this embodiment, the hybrid bridge arm also includes a controller, which is connected to the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm, and is used to control the on-state of the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm. Under the control of the controller, the hybrid bridge arm can be in different working states.

[0129] In one embodiment, a control method for a hybrid bridge arm is provided, which is used to control the hybrid bridge arm of any of the above embodiments. Specifically, when the hybrid bridge arm includes a controller, the control method for the hybrid bridge arm can be executed by the controller. The control method for the hybrid bridge arm includes the following steps:

[0130] When the hybrid bridge arm is turned on, the off current is controlled to optimize the bridge arm turning on;

[0131] After the shutdown current optimization bridge arm is completed and enters the on state, the on-voltage drop optimization bridge arm is controlled to be turned on;

[0132] After the on-state voltage drop optimization bridge arm is turned on and enters the on state, the off-state current optimization bridge arm is turned off;

[0133] as well as,

[0134] When the hybrid bridge arm is turned off, the turn-off current is controlled to optimize the bridge arm opening;

[0135] Control the on-state voltage drop to optimize the bridge arm shutdown;

[0136] After the on-state voltage drop optimized bridge arm is turned off, the turn-off current is controlled to optimize the bridge arm turn-off.

[0137] Specifically, when the hybrid bridge arm is turned on, the off-current optimization bridge arm is triggered to turn on first, and the current rising slope is controlled, thereby reducing the converter's requirements on the current rising rate protection circuit.

[0138] After the off-current optimized bridge arm is turned on and enters the on-state, the on-voltage drop optimized bridge arm is controlled to turn on. After the off-current optimized bridge arm is turned on and enters the on-state, the voltage at both ends of the hybrid bridge arm is clamped close to zero, triggering the on-voltage drop optimized bridge arm to turn on. The on-voltage drop optimized bridge arm achieves zero-voltage soft turn-on, reduces turn-on loss, and begins to shunt with the off-current optimized bridge arm. Since the on-resistance of the on-voltage drop optimized bridge arm is lower, the current flowing through the on-voltage drop optimized bridge arm is greater than that of the off-current optimized bridge arm.

[0139] After the on-state voltage drop optimization bridge arm is turned on and enters the on-state, the off-state current optimization bridge arm is controlled to be turned off. After the on-state voltage drop optimization bridge arm is turned on and enters the on-state, the off-state current optimization bridge arm is triggered to turn off. The off-state current optimization bridge arm achieves zero voltage soft shutdown, reduces the shutdown loss, and transfers all the current to the on-state voltage drop optimization bridge arm, reduces the bridge arm conduction loss and improves the converter operation efficiency.

[0140] When the hybrid bridge arm is turned off, the off current optimization bridge arm is controlled to be turned on. When the hybrid bridge arm is turned off, the off current optimization bridge arm is first triggered to be turned on, and the off current optimization bridge arm completes the zero voltage soft turn-on and starts to shunt with the on-voltage drop optimization bridge arm.

[0141] After that, the on-state voltage drop optimization bridge arm is controlled to be turned off. The on-state voltage drop optimization bridge arm is triggered to be turned off. After the on-state voltage drop optimization bridge arm completes the zero voltage soft shutdown, the current of all the hybrid bridge arms is transferred to the off current optimization bridge arm.

[0142] Finally, after the on-state voltage drop optimization bridge arm is turned off, the off-state current optimization bridge arm is controlled to turn off. The off-state current optimization bridge arm is triggered to turn off, and its large current shutdown capability is used to improve the operating range of the converter. The off-state current optimization bridge arm has a short on-state current time, which reduces the current level requirements for the component devices.

[0143] This method utilizes the controllable rise rate of the turn-on current of the turn-off current optimization bridge arm to simplify the protection circuit or even completely remove it. This method can also reduce the flow time of the turn-off current optimization bridge arm and the current level requirements of the component devices.

[0144] In one embodiment, the control method of the hybrid bridge arm further includes the following steps:

[0145] When the hybrid bridge arm is turned on, the off current is controlled to optimize the bridge arm turning on;

[0146] After the off-current optimization bridge arm is turned on and enters the on-state, the on-voltage drop optimization bridge arm is controlled to be turned on, and the off-current optimization bridge arm and the on-voltage drop optimization bridge arm are simultaneously conducting current;

[0147] as well as,

[0148] When the hybrid bridge arm is turned off, the on-state voltage drop is controlled to optimize the bridge arm turn-off;

[0149] After the on-state voltage drop optimized bridge arm is turned off, the turn-off current is controlled to optimize the bridge arm turn-off.

[0150] Specifically, when the hybrid bridge arm is turned on, the off current optimization bridge arm is controlled to be turned on. When the hybrid bridge arm is turned on, the off current optimization bridge arm is first triggered to be turned on, and the current rising slope is controlled, thereby reducing the converter's requirements on the current rising rate protection circuit.

[0151] After the off-current optimized bridge arm is turned on and enters the on-state, the on-voltage drop optimized bridge arm is controlled to be turned on, and the off-current optimized bridge arm and the on-voltage drop optimized bridge arm are simultaneously turned on. After the off-current optimized bridge arm is turned on and enters the on-state, the voltage at both ends of the hybrid bridge arm is clamped close to zero, and the on-voltage drop optimized bridge arm is triggered to turn on. The on-voltage drop optimized bridge arm achieves zero voltage soft turn-on, reduces turn-on loss, and begins to shunt with the off-current optimized bridge arm. Since the on-resistance of the on-voltage drop optimized bridge arm is lower, the current flowing through the on-voltage drop optimized bridge arm is more than that of the off-current optimized bridge arm, and the hybrid bridge arm is turned on at the same time, further reducing the bridge arm conduction loss and improving the converter operation efficiency.

[0152] When the hybrid bridge arm is turned off, the on-state voltage drop optimization bridge arm is controlled to be turned off. When the hybrid bridge arm is turned off, the on-state voltage drop optimization bridge arm is first triggered to be turned off. After the on-state voltage drop optimization bridge arm completes the zero voltage soft shutdown, the current of all the hybrid bridge arms is transferred to the off current optimization bridge arm.

[0153] Finally, after the on-state voltage drop optimization bridge arm is turned off, the off-state current optimization bridge arm is controlled to turn off. The off-state current optimization bridge arm is triggered to turn off, and its large current shutdown capability is used to improve the operating range of the converter. The amplitude of the on-state current of the off-state current optimization bridge arm is small, which partially reduces the current level requirements for the component devices.

[0154] This method utilizes the controllable rise rate of the turn-on current of the turn-off current optimization bridge arm to simplify the protection circuit and partially reduce the on-state current of the turn-off current optimization bridge arm and the current level requirements of the component devices.

[0155] In one embodiment, the control method of the hybrid bridge arm further includes the following steps:

[0156] When the hybrid bridge arm is turned on, the conduction voltage drop is controlled to optimize the bridge arm opening;

[0157] as well as,

[0158] When the hybrid bridge arm is turned off, the turn-off current is controlled to optimize the bridge arm opening;

[0159] After the shutdown current optimization bridge arm is turned on and enters the on state, the on-voltage drop optimization bridge arm is turned off;

[0160] After the on-state voltage drop optimized bridge arm is turned off, the turn-off current is controlled to optimize the bridge arm turn-off.

[0161] Specifically, when the hybrid bridge arm is turned on, the conduction voltage drop optimization bridge arm is controlled to be turned on. When the hybrid bridge arm is turned on, the conduction voltage drop optimization bridge arm is first triggered to be turned on, and the protection circuit limits the current rising slope. After the conduction voltage drop optimization bridge arm enters the conduction state, it bears the full current. The characteristics of low conduction voltage drop can reduce conduction loss and improve converter operation efficiency.

[0162] When the hybrid bridge arm is turned off, the off current optimization bridge arm is controlled to be turned on. When the hybrid bridge arm is turned off, the off current optimization bridge arm is first triggered to be turned on, and after the off current optimization bridge arm enters the on state, it is short-timely shunted with the on voltage drop optimization bridge arm.

[0163] After that, after the off-current optimized bridge arm is turned on and enters the on-state, the on-voltage drop optimized bridge arm is controlled to be turned off. The on-voltage drop optimized bridge arm is triggered to be turned off, and after the on-voltage drop optimized bridge arm completes the zero-voltage soft shutdown, the current of all the hybrid bridge arms is transferred to the off-current optimized bridge arm.

[0164] Finally, after the on-state voltage drop optimization bridge arm is turned off, the off-state current optimization bridge arm is controlled to turn off. The off-state current optimization bridge arm is triggered to turn off, and its large current shutdown capability is used to improve the operating range of the converter. The off-state current optimization bridge arm has the shortest on-state current time, which minimizes the current level requirements for the components.

[0165] This method can minimize the current conduction time of the off-current optimization bridge arm and the current level requirements of the constituent devices, while no longer requiring the on-current rising slope of the off-current optimization bridge arm to be controllable.

[0166] In one embodiment, the control method of the hybrid bridge arm further includes the following steps:

[0167] When the hybrid bridge arm is turned on, the conduction voltage drop is controlled to optimize the bridge arm opening;

[0168] After the on-state voltage drop optimization bridge arm is turned on and enters the on state, the off-state current optimization bridge arm is controlled to be turned on, and the off-state current optimization bridge arm and the on-state voltage drop optimization bridge arm are simultaneously passed through;

[0169] as well as,

[0170] When the hybrid bridge arm is turned off, the on-state voltage drop is controlled to optimize the bridge arm turn-off;

[0171] After the on-state voltage drop optimized bridge arm is turned off, the turn-off current is controlled to optimize the bridge arm turn-off.

[0172] Specifically, when the hybrid bridge arm is turned on, the conduction voltage drop optimization bridge arm is controlled to be turned on. When the hybrid bridge arm is turned on, the conduction voltage drop optimization bridge arm is first triggered to be turned on, and the protection circuit limits the current rising slope. After the conduction voltage drop optimization bridge arm enters the conduction state, the hybrid bridge arm has the characteristic of low conduction loss.

[0173] After that, after the on-state voltage drop optimized bridge arm is turned on and enters the on-state, the off-state current optimized bridge arm is controlled to be turned on, and the off-state current optimized bridge arm and the on-state voltage drop optimized bridge arm are simultaneously conducting current. The off-state current optimized bridge arm is triggered to complete the zero voltage soft turn-on, and begins to shunt current with the off-state current optimized bridge arm. Since the on-state voltage drop optimized bridge arm has a lower on-resistance, the current flowing through the on-state voltage drop optimized bridge arm is more than that through the off-state current optimized bridge arm, and the mixed bridge arm is conducting current at the same time, further reducing the bridge arm conduction loss and improving the converter operation efficiency.

[0174] When the hybrid bridge arm is turned off, the on-state voltage drop optimization bridge arm is controlled to be turned off. When the hybrid bridge arm is turned off, the on-state voltage drop optimization bridge arm is first triggered to be turned off. After the on-state voltage drop optimization bridge arm completes the zero voltage soft shutdown, the current of all the hybrid bridge arms is transferred to the off current optimization bridge arm.

[0175] Finally, after the on-state voltage drop optimization bridge arm is turned off, the off-current optimization bridge arm is controlled to turn off. The off-current optimization bridge arm is triggered to turn off, and its large current shutdown capability is used to improve the operating range of the converter.

[0176] This method can minimize the conduction voltage drop of the hybrid bridge arm and maximize the converter operation efficiency. Similarly, this method no longer requires the turn-off current optimization bridge arm to have a controllable turn-on current rising slope.

[0177] In one embodiment, a half-bridge circuit is provided, comprising an upper bridge arm and a lower bridge arm connected in series, wherein at least one of the upper bridge arm and the lower bridge arm is a hybrid bridge arm as described above. Figure 2 As shown, both the upper bridge arm and the lower bridge arm are hybrid bridge arm 1; or, the upper bridge arm is hybrid bridge arm 1 and the lower bridge arm is non-hybrid bridge arm; or, the upper bridge arm is non-hybrid bridge arm and the lower bridge arm is hybrid bridge arm 1. The common end of the upper bridge arm and the lower bridge arm is used as the midpoint of the half-bridge circuit 2 and is connected to the AC port 6 through the LC filter 5.

[0178] In one embodiment, a current source converter is provided, comprising a half-bridge circuit 2 as in any of the above embodiments. The half-bridge circuit 2 of the current source converter is a component of the current source converter.

[0179] In one embodiment, the number of the half-bridge circuits 2 is three, and each half-bridge circuit 2 is connected in parallel. The three half-bridge circuits 2 are connected in parallel to form the power electronic part of the current source converter, and the two ends of each half-bridge circuit 2 are connected to the DC port 4 through the smoothing reactor 3, and the midpoint of each half-bridge circuit 2 is connected to the AC port 6 through the LC filter 5.

[0180] The half-bridge circuit 2 of the current source converter includes an upper bridge arm and a lower bridge arm connected in series, and at least one of the upper bridge arm and the lower bridge arm is a hybrid bridge arm 1. That is, both the upper bridge arm and the lower bridge arm are hybrid bridge arms 1; or, the upper bridge arm is a hybrid bridge arm 1, and the lower bridge arm is a non-hybrid bridge arm; or, the upper bridge arm is a non-hybrid bridge arm, and the lower bridge arm is a hybrid bridge arm 1. The common end of the upper bridge arm and the lower bridge arm is used as the midpoint of the half-bridge circuit 2, and is connected to the AC port 6 through the LC filter 5.

[0181] When the current source converter is operating in a steady state, the current amplitude of the smoothing reactor 3 is approximately constant. When the upper bridge arm of the half-bridge circuit 2 is turned on and the lower bridge arm is blocked, a positive current is injected into the corresponding phase AC port 6, and the current amplitude is the same as that of the smoothing reactor 3; when the lower bridge arm of the half-bridge circuit 2 is turned on and the upper bridge arm is blocked, a negative current is injected into the corresponding phase AC port 6, and the current amplitude is the same as that of the smoothing reactor 3; when the upper and lower bridge arms of the half-bridge circuit 2 are turned on at the same time, the smoothing reactor 3 continues the current through the short-circuited half-bridge circuit 2, and the current amplitude injected into the corresponding phase AC port 6 is zero.

[0182] When the switch states of the upper and lower arms remain unchanged, the injected current generates conduction loss on the conduction voltage drop of the upper and lower arms; when the switch states of the upper and lower arms are switched, the device actively shuts down to complete the current transfer. Therefore, the conduction voltage drop and shutdown capability of the upper and lower arms are key parameters. A lower conduction voltage drop can improve the efficiency of the current source converter, reduce the heat dissipation power requirement and operating cost; a higher shutdown capability can expand the operating range of the current source converter, improve fault resistance and operating reliability. The upper and lower arms have four states, namely, on, off, conduction and blocking, among which on and off are transient processes, and on and blocking are stable states. Switching from conduction to blocking is off, and switching from blocking to conduction is on.

[0183] In order to better understand the above embodiment, a detailed explanation is given below in conjunction with a specific embodiment. In one embodiment, the present application is based on the technical idea of ​​reducing the on-state voltage drop of the bridge arm of the current source converter while improving its current shutdown capability, and proposes a hybrid bridge arm and its control method, a half-bridge circuit and a current source converter. The specific technical solution is to connect a bridge arm with a low on-state voltage drop and a bridge arm with a high current shutdown capability in parallel to form a hybrid bridge arm, and the hybrid bridge arm constitutes a current source converter. The bridge arm with a low on-state voltage drop and the bridge arm with a high current shutdown capability use power semiconductor devices with different superior performance parameters.

[0184] An embodiment of a current source converter composed of a hybrid bridge arm of the present application is shown in FIG2 , where the hybrid bridge arm 1 is connected in series to form a half-bridge circuit, and three half-bridge circuits are connected in parallel to form a current source converter. The hybrid bridge arm 1 is composed of a group of on-state voltage drop optimized bridge arms 11 and a group of off-state current optimized bridge arms 12 connected in parallel.

[0185] The topological structure of the on-state voltage drop optimized bridge arm 11 is shown in FIG3 , which is composed of a reverse resistance fully controlled power semiconductor device 111 with a low on-state voltage drop and a protection circuit 112 in series, and the number of series stages is ≥ 1, including but not limited to a reverse resistance IGCT and a reverse conducting or asymmetric IGCT in series with a diode.

[0186] The topological structure of the turn-off current optimized bridge arm 12 is shown in FIG4 , which is composed of a reverse-resistance fully-controlled power semiconductor device 121 with a large turn-off current or a low turn-off loss and a protection circuit 122 in series, and the number of series stages is ≥ 1, including but not limited to reverse-resistance IGBT, asymmetric IGBT series diode, MOSFET series diode, emitter-turn-off thyristor series diode and diode-assisted turn-off thyristor, etc.

[0187] The on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 include unspecified series voltage equalization and / or parallel current equalization circuits, and their power semiconductor devices 111 and 112 can be connected in parallel to expand the maximum allowable current of the bridge arm, and the parallel number is ≥1.

[0188] The protection circuit is generally a current rise rate protection circuit, which can be respectively protection circuits 111 and 112 as shown in FIG3 and FIG4 and connected in series in the on-state voltage drop optimization bridge arm 11 and the off-state current optimization bridge arm 12, or can be concentrated as a protection circuit 13 directly connected in series with the hybrid bridge arm as shown in FIG5. When the protection circuit 13 is directly connected in series with the hybrid bridge arm, the protection circuits in the on-state voltage drop optimization bridge arm 11 and the off-state current optimization bridge arm 12 can be retained as shown in FIG3 and FIG4, or can be removed as shown in FIG6 and FIG7. The following is an explanation in conjunction with several detailed embodiments:

[0189] Embodiment 1:

[0190] One working mode of the current source converter composed of the hybrid bridge arm of the present application is as follows:

[0191] a) When the hybrid bridge arm 1 is turned on, the off-current optimization bridge arm 12 is triggered to turn on first, and the current rising slope is controlled, thereby reducing the requirements of the converter on the current rising rate protection circuit;

[0192] b) After the off-current optimized bridge arm 12 is turned on and enters the on state, the voltage across the hybrid bridge arm 1 is clamped close to zero, triggering the on-voltage drop optimized bridge arm 11 to turn on. The on-voltage drop optimized bridge arm 11 achieves zero-voltage soft turn-on, reduces turn-on loss, and begins to shunt current with the off-current optimized bridge arm 12. Since the on-resistance of the on-voltage drop optimized bridge arm 11 is lower, the current flowing through the on-voltage drop optimized bridge arm 11 is greater than that of the off-current optimized bridge arm 12;

[0193] c) After the on-state voltage drop optimized bridge arm 11 is turned on and enters the on state, the off-state current optimized bridge arm 12 is triggered to turn off, and the off-state current optimized bridge arm 12 realizes zero voltage soft shutdown, reduces the shutdown loss and transfers all the current to the on-state voltage drop optimized bridge arm 11, reduces the bridge arm conduction loss and improves the converter operation efficiency;

[0194] d) When the hybrid bridge arm 1 is turned off, the off-current optimization bridge arm 12 is first triggered to turn on, and the off-current optimization bridge arm 12 completes the zero-voltage soft turn-on and starts to shunt with the on-voltage drop optimization bridge arm 11;

[0195] e) then triggering the on-state voltage drop optimized bridge arm 11 to turn off, and after the on-state voltage drop optimized bridge arm 11 completes the zero voltage soft shutdown, the current of the entire hybrid bridge arm 1 is transferred to the off-state current optimized bridge arm 12;

[0196] f) Finally, the shutdown current optimization bridge arm 12 is triggered to shut down, and its large current shutdown capability is used to improve the operating range of the converter. The shutdown current optimization bridge arm 12 has a short current conduction time, which reduces the current level requirements for the component devices.

[0197] At this time, the preferred type of device constituting the off-current optimized bridge arm 12 is a reverse-resistance fully-controlled power semiconductor device with controllable current rise slope, including but not limited to reverse-resistance IGBT, asymmetric IGBT series diode, and MOSFET series diode. This method uses the controllable on-current rise rate of the off-current optimized bridge arm 12 to simplify the protection circuit or even completely remove it. The topological structures of the hybrid bridge arm 1, the on-voltage drop optimized bridge arm 11, and the off-current optimized bridge arm 12 are shown in Figure 2, Figure 6 As shown in Figure 7. In addition, this method can also reduce the current flow time of the turn-off current optimization bridge arm 12 and the current level requirements of the component devices.

[0198] Embodiment 2:

[0199] One working mode of the current source converter composed of the hybrid bridge arm of the present application is as follows:

[0200] a) When the hybrid bridge arm 1 is turned on, the off-current optimization bridge arm 12 is triggered to turn on first, and the current rising slope is controlled, thereby reducing the requirements of the converter on the current rising rate protection circuit;

[0201] b) After the off-current optimized bridge arm 12 is turned on and enters the on-state, the voltage at both ends of the hybrid bridge arm 1 is clamped close to zero, and the on-voltage drop optimized bridge arm 11 is triggered to turn on. The on-voltage drop optimized bridge arm 11 achieves zero voltage soft turn-on, reduces the turn-on loss, and begins to shunt with the off-current optimized bridge arm 12. Since the on-resistance of the on-voltage drop optimized bridge arm 11 is lower, the current flowing through the on-voltage drop optimized bridge arm 11 is greater than that of the off-current optimized bridge arm 12, and the hybrid bridge arms are simultaneously conducting, further reducing the bridge arm conduction loss and improving the converter operation efficiency;

[0202] c) When the hybrid bridge arm 1 is turned off, the on-state voltage drop optimized bridge arm 11 is first triggered to turn off. After the on-state voltage drop optimized bridge arm 11 completes the zero voltage soft shutdown, the current of the entire hybrid bridge arm 1 is transferred to the off current optimized bridge arm 12;

[0203] d) Finally, the off-current optimization bridge arm 12 is triggered to shut down, and its large current shutdown capability is used to improve the operating range of the converter. The amplitude of the on-current of the off-current optimization bridge arm 12 is small, which partially reduces the current level requirements for the component devices.

[0204] This method uses the controllable increase rate of the on-current of the off-current optimized bridge arm 12 to simplify the protection circuit and partially reduce the on-state current of the off-current optimized bridge arm 12 and the current level requirements of the components. Similarly, this method uses the controllable increase rate of the on-current of the off-current optimized bridge arm 12 to simplify the protection circuit or even completely remove it. The topological structures of the hybrid bridge arm 1, the on-voltage drop optimized bridge arm 11 and the off-current optimized bridge arm 12 are shown in Figures 2, 6 and 7 respectively. In addition, this method can also reduce the on-current time of the off-current optimized bridge arm 12 and the current level requirements of the components.

[0205] Embodiment three:

[0206] One working mode of the current source converter composed of the hybrid bridge arm of the present application is as follows:

[0207] a) When the hybrid bridge arm 1 is turned on, the on-state voltage drop optimization bridge arm 11 is first triggered to turn on, and the protection circuit limits the current rising slope. After the on-state voltage drop optimization bridge arm 11 enters the on-state, it bears the full current. The on-state voltage drop characteristic can reduce the conduction loss and improve the converter operation efficiency;

[0208] b) When the hybrid bridge arm 1 is turned off, the off-current optimized bridge arm 12 is first triggered to turn on. After the off-current optimized bridge arm 12 enters the on-state, it is short-timely shunted with the on-voltage drop optimized bridge arm 11;

[0209] c) then triggering the on-state voltage drop optimized bridge arm 11 to turn off, and after the on-state voltage drop optimized bridge arm 11 completes the zero voltage soft shutdown, the current of the entire hybrid bridge arm 1 is transferred to the off-state current optimized bridge arm 12;

[0210] d) Finally, the current-optimizing bridge arm 12 is triggered to shut down, and its large current shut-off capability is used to improve the operating range of the converter. The current-optimizing bridge arm 12 conducts the shortest current for the shortest time, thereby minimizing the current level requirements for the component devices.

[0211] This method can minimize the current conduction time of the turn-off current optimization bridge arm 12 and the current level requirements of the components, and at the same time, it is no longer required that the turn-on current rising slope of the turn-off current optimization bridge arm 12 be controllable. The optional device types are not limited to reverse resistance IGBT, asymmetric IGBT series diode, MOSFET series diode, and can also be extended to emitter turn-off thyristor series diode and diode assisted turn-off thyristor. A specific implementation scheme of the protection circuit is shown in Figure 8, which is a saturated reactor, which can be arranged in a centralized or decentralized manner.

[0212] Embodiment 4:

[0213] One working mode of the current source converter composed of the hybrid bridge arm of the present application is as follows:

[0214] a) When the hybrid bridge arm 1 is turned on, the conduction voltage drop optimization bridge arm 11 is first triggered to turn on, and the protection circuit limits the current rising slope. After the conduction voltage drop optimization bridge arm 11 enters the conduction state, the hybrid bridge arm 1 has the characteristic of low conduction loss;

[0215] b) After that, the off-current optimized bridge arm 12 is triggered to complete the zero-voltage soft-turn-on, and starts to shunt current with the off-current optimized bridge arm 12. Since the on-resistance of the on-voltage drop optimized bridge arm 11 is lower, the current flowing through the on-voltage drop optimized bridge arm 11 is greater than that of the off-current optimized bridge arm 12, and the mixed bridge arm is simultaneously conducting, further reducing the bridge arm conduction loss and improving the converter operation efficiency;

[0216] c) When the hybrid bridge arm 1 is turned off, the on-state voltage drop optimized bridge arm 11 is first triggered to turn off. After the on-state voltage drop optimized bridge arm 11 completes the zero voltage soft shutdown, the current of the entire hybrid bridge arm 1 is transferred to the off current optimized bridge arm 12;

[0217] d) Finally, the current-optimizing bridge arm 12 is triggered to turn off, and its large current shutoff capability is utilized to improve the operating range of the converter.

[0218] This method can maximize the low on-state voltage drop current flow time and maximize the converter operation efficiency. Similarly, this method no longer requires that the turn-on current rising slope of the turn-on current optimization bridge arm 12 is controllable, and the optional device types are not limited to reverse resistance IGBT, asymmetric IGBT series diode, MOSFET series diode, and can also be extended to emitter turn-off thyristor series diode and diode assisted turn-off thyristor. A specific implementation scheme of the protection circuit is shown in Figure 8, which is a saturated reactor, which can be arranged in a centralized or decentralized manner.

[0219] Embodiment five:

[0220] A method for implementing the on-state voltage drop optimization bridge arm 11 and the off-state current optimization bridge arm 12 of the current source converter of the present application is shown in Figure 9. The power semiconductor device is connected in parallel with the series voltage equalization circuit to form bridge arm sub-units 111 and 112. The series voltage equalization circuit includes a dynamic voltage equalization circuit formed by a dynamic voltage equalization resistor 1111 and a dynamic voltage equalization capacitor 11112 connected in series, a static voltage equalization circuit composed of a static voltage equalization resistor 1113, and a voltage clamping circuit implemented by a lightning arrester 1114.

[0221] The dynamic voltage balancing circuit is used to slow down the rate of change of the voltage across the power semiconductor device during the turn-on and turn-off transients, thereby reducing the dynamic voltage difference between the devices. When the power semiconductor device is in the turn-off transient state, the voltage across the two ends rises and charges the dynamic voltage balancing capacitor 11112 through the dynamic voltage balancing resistor 1111. The dynamic voltage balancing circuit provides an additional current path to reduce the equivalent input impedance and the rate of rise of the voltage across the two ends of the power semiconductor device. When the power semiconductor device is in the turn-on transient state, the voltage across the two ends drops and discharges the dynamic voltage balancing capacitor 11112 through the resistor 1111. The dynamic voltage balancing circuit provides an additional current source to reduce the equivalent output impedance and the rate of drop of the voltage across the two ends of the power semiconductor device.

[0222] The resistance value of the static voltage balancing resistor 1113 in the static voltage balancing circuit is much smaller than the equivalent impedance when the power semiconductor device is blocked, and can balance the leakage current of the power semiconductor device when it is blocked, thereby reducing the static voltage difference between the devices.

[0223] The equivalent impedance of the lightning arrester 1114 in the voltage clamping circuit decreases as the voltage across the two ends increases, which is used to limit the further increase of the voltage across the two ends of the overvoltage power semiconductor device during the shutdown transient, forcing other devices in the series branch to withstand the voltage, thereby making the voltage across the two ends of each device approach.

[0224] Embodiment six:

[0225] A method for implementing the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 of the current source converter of the present application is shown in Figure 10. The power semiconductor device is connected in parallel with the series voltage equalization circuit to form bridge arm sub-units 111 and 112. The series voltage equalization circuit includes a dynamic voltage equalization circuit formed by connecting a dynamic voltage equalization resistor 1111 and a diode 1115 in parallel and then in series with a dynamic voltage equalization capacitor 11112, a static voltage equalization circuit composed of a static voltage equalization resistor 1113, and a voltage clamping circuit implemented by a lightning arrester 1114.

[0226] The dynamic voltage balancing circuit is used to slow down the rate of change of the voltage across the power semiconductor device during the turn-on and turn-off transients, thereby reducing the dynamic voltage difference between the devices. When the power semiconductor device is in the turn-off transient state, the voltage across the two ends rises and charges the dynamic voltage balancing capacitor 11112 through the diode 1115. The dynamic voltage balancing circuit provides an additional current path to reduce the equivalent input impedance and the rate of rise of the voltage across the two ends of the power semiconductor device. When the power semiconductor device is in the turn-on transient state, the voltage across the two ends drops and discharges the dynamic voltage balancing capacitor 11112 through the resistor 1111. The dynamic voltage balancing circuit provides an additional current source to reduce the equivalent output impedance and the rate of drop of the voltage across the two ends of the power semiconductor device.

[0227] The resistance value of the static voltage balancing resistor 1113 in the static voltage balancing circuit is much smaller than the equivalent impedance when the power semiconductor device is blocked, and can balance the leakage current of the power semiconductor device when it is blocked, thereby reducing the static voltage difference between the devices.

[0228] The equivalent impedance of the lightning arrester 1114 in the voltage clamping circuit decreases as the voltage across the two ends increases, which is used to limit the further increase of the voltage across the two ends of the overvoltage power semiconductor device during the shutdown transient, forcing other devices in the series branch to withstand the voltage, thereby making the voltage across the two ends of each device approach.

[0229] Embodiment seven:

[0230] An implementation method of the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 of the current source converter of the present application is shown in Figure 11. Two groups of power semiconductor devices in the same on-state voltage drop optimized bridge arm or two groups of power semiconductor devices in the same off-state current optimized bridge arm are respectively connected in series with windings 1116 and 1117 and then connected in parallel to form bridge arm sub-units 111 and 112. Winding 1116 and winding 1117 are reverse coupled.

[0231] When the power semiconductor device connected in series with winding 1116 is turned on faster, a reverse electromotive force will be generated on winding 1117. This electromotive force strengthens the positive effect of the voltage at both ends of the bridge arm sub-unit on the current rise rate of the power semiconductor device connected in series with winding 1117, and vice versa, ultimately achieving a dynamic balance of current in the turn-on process and conduction state of the two groups of power semiconductor devices.

[0232] The half-bridge circuit and current source converter provided in the present application can increase the off-current while reducing the on-voltage drop of the bridge arm, and at the same time optimize the operating efficiency and operating range of the current source converter.

[0233] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0234] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0235] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A hybrid bridge arm, characterized in that: Applied to current source converter; The hybrid bridge arm includes a conduction voltage drop optimized bridge arm and a turn-off current optimized bridge arm in parallel, the conduction voltage drop of the conduction voltage drop optimized bridge arm is smaller than the conduction voltage drop of the turn-off current optimized bridge arm, and the current turn-off capability of the turn-off current optimized bridge arm is higher than the current turn-off capability of the conduction voltage drop optimized bridge arm.

2. The hybrid bridge arm according to claim 1, characterized in that: The on-state voltage drop optimization bridge arm and the off-state current optimization bridge arm have different structures.

3. The hybrid bridge arm according to claim 1, characterized in that: The on-state voltage drop optimization bridge arm and the off-state current optimization bridge arm are both turnable bridge arms.

4. The hybrid bridge arm according to claim 1, characterized in that: The on-state voltage drop optimized bridge arm includes a first type of reverse resistance fully-controlled power semiconductor device, which is a reverse resistance fully-controlled power semiconductor device with an on-state voltage drop less than a preset on-state voltage drop threshold.

5. The hybrid bridge arm according to claim 4, characterized in that: One of the on-state voltage drop optimized bridge arms includes a plurality of the first-type reverse resistance fully-controlled power semiconductor devices, and each of the first-type reverse resistance fully-controlled power semiconductor devices is connected in series.

6. The hybrid bridge arm according to claim 4, characterized in that: The on-state voltage drop optimized bridge arm also includes a protection circuit, and the protection circuit is connected in series with the first type of reverse resistance fully controlled power semiconductor device.

7. The hybrid bridge arm according to claim 1, characterized in that: The shutdown current optimized bridge arm includes a second type of reverse resistance fully controlled power semiconductor device, which is a reverse resistance fully controlled power semiconductor device with a shutdown current greater than a preset shutdown current threshold, or a shutdown loss lower than a preset shutdown loss threshold.

8. The hybrid bridge arm according to claim 7, characterized in that: One of the turn-off current optimization bridge arms includes a plurality of the second-type reverse-resistance fully-controlled power semiconductor devices, and each of the second-type reverse-resistance fully-controlled power semiconductor devices is connected in series.

9. The hybrid bridge arm according to claim 7, characterized in that: The off-current optimized bridge arm also includes a protection circuit, which is connected in series with the second-type reverse resistance fully controlled power semiconductor device.

10. The hybrid bridge arm according to claim 1, characterized in that: It also includes a protection circuit, which is connected in series with the parallel on-voltage drop optimization bridge arm and the off-current optimization bridge arm.

11. The hybrid bridge arm according to claim 10, characterized in that: The protection circuit is a reactor.

12. The hybrid bridge arm according to claim 1, characterized in that: It also includes a controller, which is connected to the on-state voltage drop optimization bridge arm and the off-state current optimization bridge arm and is used to control the on-state of the on-state voltage drop optimization bridge arm and the off-state current optimization bridge arm.

13. The hybrid bridge arm according to claim 1, characterized in that: It also includes a series voltage balancing circuit, which is connected in parallel with the power semiconductor device in the hybrid bridge arm.

14. The hybrid bridge arm according to claim 13, characterized in that: The series voltage balancing circuit includes a dynamic voltage balancing circuit, a static voltage balancing circuit and a voltage clamping circuit. The dynamic voltage balancing circuit, the static voltage balancing circuit and the voltage clamping circuit are all connected in parallel with the power semiconductor device.

15. The hybrid bridge arm according to claim 14, characterized in that: The dynamic voltage balancing circuit includes a dynamic voltage balancing resistor and a dynamic voltage balancing capacitor. The structure formed by the dynamic voltage balancing resistor and the dynamic voltage balancing capacitor being connected in series is connected in parallel with the power semiconductor device.

16. The hybrid bridge arm according to claim 15, characterized in that: The dynamic voltage balancing circuit also includes a diode, which is connected in parallel with the dynamic voltage balancing resistor.

17. The hybrid bridge arm according to claim 1, characterized in that: It also includes a parallel current sharing circuit, which is connected in series with the power semiconductor device in the on-state voltage drop optimization bridge arm or the off-state current optimization bridge arm.

18. The hybrid bridge arm according to claim 17, characterized in that: The parallel current balancing circuit includes a first winding and a second winding, and the first winding and the second winding are respectively connected in series with power semiconductor devices on different branches in the on-state voltage drop optimization bridge arm; or, the first winding and the second winding are respectively connected in series with power semiconductor devices on different branches in the off-state current optimization bridge arm; the first winding and the second winding are reversely coupled.

19. A control method for a hybrid bridge arm, characterized in that: The method comprises: When the hybrid bridge arm is turned on, the off current is controlled to optimize the bridge arm turning on; After the off-current optimization bridge arm is turned on and enters the on state, controlling the on-voltage drop optimization bridge arm to turn on; After the on-state voltage drop optimization bridge arm is turned on and enters the on state, controlling the off-state current optimization bridge arm to turn off; as well as, When the hybrid bridge arm is turned off, controlling the turn-off current to optimize the bridge arm opening; Controlling the conduction voltage drop to optimize the bridge arm shutdown; After the on-state voltage drop optimization bridge arm is turned off, the off-state current optimization bridge arm is controlled to be turned off.

20. The method according to claim 19, characterized in that The method further comprises: When the hybrid bridge arm is turned on, controlling the off current to optimize the bridge arm to turn on; After the off-current optimized bridge arm is turned on and enters the on-state, the on-voltage drop optimized bridge arm is controlled to be turned on, and the off-current optimized bridge arm and the on-voltage drop optimized bridge arm are simultaneously conducting current; as well as, When the hybrid bridge arm is turned off, controlling the conduction voltage drop to optimize the bridge arm turn off; After the on-state voltage drop optimization bridge arm is turned off, the off-state current optimization bridge arm is controlled to be turned off.

21. The method according to claim 19, characterized in that The method further comprises: When the hybrid bridge arm is turned on, controlling the conduction voltage drop optimization bridge arm to turn on; as well as, When the hybrid bridge arm is turned off, controlling the turn-off current to optimize the bridge arm opening; After the off-current optimization bridge arm is turned on and enters the on state, controlling the on-voltage drop optimization bridge arm to turn off; After the on-state voltage drop optimization bridge arm is turned off, the off-state current optimization bridge arm is controlled to be turned off.

22. The method according to claim 19, characterized in that The method further comprises: When the hybrid bridge arm is turned on, controlling the conduction voltage drop optimization bridge arm to turn on; After the on-state voltage drop optimization bridge arm is turned on and enters the on state, the off-state current optimization bridge arm is controlled to be turned on, and the off-state current optimization bridge arm and the on-state voltage drop optimization bridge arm are simultaneously conducting current; as well as, When the hybrid bridge arm is turned off, controlling the conduction voltage drop to optimize the bridge arm turn off; After the on-state voltage drop optimization bridge arm is turned off, the off-state current optimization bridge arm is controlled to be turned off.

23. A half-bridge circuit, characterized in that: It comprises an upper bridge arm and a lower bridge arm connected in series, wherein at least one of the upper bridge arm and the lower bridge arm is a hybrid bridge arm as claimed in any one of claims 1 to 17.

24. A current source converter, characterized in that: Comprising a half-bridge circuit as claimed in claim 23.

25. The current source converter according to claim 24, characterized in that: The number of the half-bridge circuits is three, and the half-bridge circuits are connected in parallel.

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