Hybrid bridge arm and method of controlling the same, half-bridge circuit and current source converter

Abstract

The application 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 a series connection of an upper bridge arm and a lower bridge arm. 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 an off current optimization bridge arm in parallel connection. The conduction voltage drop of the conduction voltage drop optimization bridge arm is smaller than the conduction voltage drop of the off current optimization bridge arm. The off current capability of the off current optimization bridge arm is higher than the off current capability of the conduction voltage drop optimization bridge arm. The hybrid bridge arm is formed by connecting the conduction voltage drop optimization bridge arm with low conduction voltage drop and the off current optimization bridge arm with high off current capability in parallel connection. The current source type converter is composed of the hybrid bridge arm. The current source type converter can improve the off current capability while reducing the conduction voltage drop, realizes the simultaneous optimization of the operation efficiency and the operation range of the current source type converter, and improves the upper limit of the working performance constraint of the current source type converter.

Description

Technical Field

[0001] This application relates to the field of converter technology, and in particular to a hybrid bridge arm and its control method, a half-bridge circuit, and a current source converter. Background Technology

[0002] Current source converters are a type of converter with high capacity per unit area and the ability to effectively handle DC short-circuit faults without shutting down. They have significant technical advantages in applications such as wind power transmission and offshore wind power grid connection.

[0003] Traditional current-source converters employ a direct-connect topology. The bridge arms are composed of power semiconductor devices connected in series; two sets of bridge arms in series form a half-bridge, and three sets of half-bridges in parallel form the power electronics section of the current-source converter. When the switching state of the bridge arms remains constant, the injected current generates conduction losses across the on-state voltage drop of the bridge arm; when the switching state of the bridge arm changes, the device actively turns off to complete the current transfer. The power semiconductor devices that make up the bridge arms cannot simultaneously achieve both turn-off capability and on-state voltage drop, thus creating a trade-off between optimizing converter operating efficiency and operating range, resulting in a performance constraint upper limit for traditional current-source converters. Summary of the Invention

[0004] Therefore, it is necessary to address the technical problem of the upper limit of the operating performance of traditional current source converters by providing a hybrid bridge arm and its control method, half-bridge circuit and current source converter that can improve the upper limit of the operating performance of current source converters.

[0005] Firstly, this application provides a hybrid bridge arm for use in a current source converter;

[0006] The hybrid bridge arm includes a parallel on-state voltage drop optimized bridge arm and a turn-off current optimized bridge arm. The on-state voltage drop of the on-state voltage drop optimized bridge arm is less than the on-state 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 that of the on-state voltage drop optimized bridge arm.

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

[0008] In one embodiment, both the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm are turn-off bridge arms.

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

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

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

[0012] In one embodiment, the turn-off current optimized bridge arm includes a second type of fully controllable reverse resistance power semiconductor device, which is a fully controllable reverse resistance 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.

[0013] In one embodiment, one of the shutdown current optimized bridge arms includes a plurality of second-type fully controllable reverse-resistance power semiconductor devices, each of which is connected in series.

[0014] In one embodiment, the turn-off current optimized bridge arm further includes a protection circuit connected in series with the second type of reverse-resistance fully controlled power semiconductor device.

[0015] In one embodiment, the hybrid arm further includes a protection circuit connected in series with the parallel on-state voltage drop optimized arm and the off-state current optimized arm.

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

[0017] In one embodiment, the hybrid bridge arm further includes a controller connected to the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm, for controlling the on-state of the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm.

[0018] In one embodiment, the hybrid arm further includes a series voltage equalization circuit connected in parallel with the power semiconductor devices in the hybrid arm.

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

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

[0021] In one embodiment, the dynamic voltage equalization circuit further includes a diode connected in parallel with the dynamic voltage equalization resistor.

[0022] In one embodiment, the hybrid arm further includes a parallel current sharing circuit connected in series with the power semiconductor device in the on-state voltage drop optimized arm or the off-state current optimized arm.

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

[0024] Secondly, this application provides a control method for a hybrid bridge arm, the method comprising:

[0025] When the hybrid bridge arm is turned on, the turn-off current is controlled to optimize the bridge arm turn-on.

[0026] After the turn-off current optimized bridge arm completes the turn-on and enters the conduction state, the conduction voltage drop optimized bridge arm is turned on.

[0027] After the optimized on-voltage drop bridge arm completes the on-state and enters the on-state, the optimized off-current bridge arm is controlled to turn off.

[0028] as well as,

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

[0030] Controlling the on-state voltage drop optimizes bridge arm turn-off;

[0031] After the optimized on-voltage drop bridge arm completes the turn-off, the optimized turn-off current bridge arm is controlled to turn off.

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

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

[0034] After the turn-off current optimized bridge arm completes the turn-on and enters the conduction state, the conduction voltage drop optimized bridge arm is controlled to turn on, and the turn-off current optimized bridge arm and the conduction voltage drop optimized bridge arm simultaneously carry current.

[0035] as well as,

[0036] When the hybrid bridge arm is turned off, the on-state voltage drop is controlled to optimize the bridge arm turn-off;

[0037] After the optimized on-voltage drop bridge arm completes the turn-off, the optimized turn-off current bridge arm is controlled to turn off.

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

[0039] When the hybrid bridge arm is turned on, the on-state voltage drop is controlled to optimize the bridge arm turn-on;

[0040] as well as,

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

[0042] After the turn-off current optimized bridge arm completes the turn-on and enters the conduction state, the conduction voltage drop optimized bridge arm is controlled to turn off.

[0043] After the optimized on-voltage drop bridge arm completes the turn-off, the optimized turn-off current bridge arm is controlled to turn off.

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

[0045] When the hybrid bridge arm is turned on, the on-state voltage drop is controlled to optimize the bridge arm turn-on;

[0046] 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 turned on, and the off-state current optimized bridge arm and the on-state voltage drop optimized bridge arm are simultaneously flowing.

[0047] as well as,

[0048] When the hybrid bridge arm is turned off, the on-state voltage drop is controlled to optimize the bridge arm turn-off;

[0049] After the optimized on-voltage drop bridge arm completes the turn-off, the optimized turn-off current bridge arm is controlled to turn off.

[0050] Thirdly, this application provides a half-bridge circuit, including 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] Fourthly, this application provides a current source converter, including the half-bridge circuit described above.

[0052] The aforementioned hybrid bridge arm and its control method, half-bridge circuit, and current-source converter, wherein the hybrid bridge arm of the current-source converter includes a parallel on-state voltage drop optimized bridge arm and a turn-off current optimized bridge arm. The on-state voltage drop of the on-state voltage drop optimized bridge arm is smaller than that 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 that of the on-state voltage drop optimized bridge arm. The advantageous performance parameters of the on-state voltage drop optimized bridge arm and the turn-off current optimized bridge arm differ. By paralleling the low on-state voltage drop optimized bridge arm and the high current turn-off capability turn-off current optimized bridge arm to form a hybrid bridge arm, which, as a component of the current-source converter, allows the current-source converter to improve its current turn-off capability while reducing the on-state voltage drop, achieving simultaneous optimization of the operating efficiency and operating range of the current-source converter, and raising the upper limit of the operating performance constraints of the current-source converter. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

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

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

[0057] Figure 4 This is a schematic diagram of the structure of the bridge arm with optimized turn-off current in one embodiment;

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

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

[0060] Figure 7 This is a schematic diagram of the structure of the bridge arm with optimized turn-off current in another embodiment;

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

[0062] Figure 9This is a partial structural diagram of the hybrid bridge arm in one embodiment;

[0063] Figure 10 This is a partial structural diagram of the hybrid bridge arm in another embodiment;

[0064] Figure 11 This is a partial structural diagram of the hybrid bridge arm in another embodiment. Detailed Implementation

[0065] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0067] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. 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 is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0069] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0070] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0071] The hybrid bridge arm 1 provided in this application embodiment is a component of a current source converter. Exemplarily, two hybrid bridge arms connected in series can form a half-bridge circuit. Alternatively, a hybrid bridge arm and a diode bridge arm can also form a half-bridge circuit. The half-bridge circuit is a component of a current source converter. Exemplarily, such as... Figure 1 As shown, there are three half-bridge circuits 2. The three half-bridge circuits 2 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 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.

[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, wherein at least one of the upper and lower bridge arms is a hybrid bridge arm 1. That is, as shown in the figure... Figure 2 As shown, both the upper and lower bridge arms 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 terminal of the upper and lower bridge arms serves 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 steady state, the current amplitude of the smoothing reactor 3 is approximately constant. When the upper arm of the half-bridge circuit 2 is turned on and the lower 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 arm of the half-bridge circuit 2 is turned on and the upper 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 both the upper and lower arms of the half-bridge circuit 2 are turned on, the smoothing reactor 3 continues to flow 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 switching states of the upper and lower bridge arms remain unchanged, the injected current generates conduction losses across the on-state voltage drops of the upper and lower bridge arms. When the switching states of the upper and lower bridge arms switch, the devices actively turn off to complete the current transfer. Therefore, the on-state voltage drop and turn-off capability of the upper and lower bridge arms are key parameters. A lower on-state voltage drop can improve the efficiency of the current source converter, reduce heat dissipation power requirements and operating costs; a higher turn-off capability can extend the operating range of the current source converter, improve fault tolerance and operational reliability. The upper and lower bridge arms have four states: on, off, conduction, and blocking. On and off are transient processes, while conduction and blocking are steady 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 parallel-connected on-state voltage drop optimized bridge arm 11 and a turn-off current optimized bridge arm 12. The on-state voltage drop of the on-state voltage drop optimized bridge arm 11 is smaller than that of the turn-off current optimized bridge arm 12, while the current turn-off capability of the turn-off current optimized bridge arm 12 is higher than that of the on-state voltage drop optimized bridge arm 11. Specifically, the advantageous performance parameters of the on-state voltage drop optimized bridge arm 11 and the turn-off current optimized bridge arm 12 can be made different by setting different structures. The advantageous performance parameter of the on-state voltage drop optimized bridge arm 11 is the on-state voltage drop, while 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 turn-off current, turn-off loss, or turn-off speed. A high current turn-off capability can be reflected by a large turn-off current, low turn-off loss, or fast turn-off speed.

[0076] For example, one operating mode of hybrid bridge arm 1 is as follows: When hybrid bridge arm 1 is turned on, the turn-off current optimization bridge arm 12 is first triggered to turn on, and the current rise rate is controlled, reducing the requirements of the converter on the current rise rate protection circuit. After the turn-off current optimization bridge arm 12 completes its turn-on and enters the conduction state, the voltage across hybrid bridge arm 1 is clamped close to zero. At this time, the on-state voltage drop optimization bridge arm 11 is triggered to turn on. The on-state voltage drop optimization bridge arm 11 achieves zero-voltage soft turn-on, reducing turn-on losses and starting to shunt current with the turn-off current optimization bridge arm 12. Since the on-state voltage drop optimization bridge arm 11 has a lower conduction impedance, the current flowing through the on-state voltage drop optimization bridge arm 11 is more than that through the turn-off current optimization bridge arm 12. After the on-state voltage drop optimization bridge arm 11 completes its turn-on and enters the conduction state, the turn-off current optimization bridge arm 12 is triggered to turn off. The turn-off current optimization bridge arm 12 achieves zero-voltage soft turn-off, reducing turn-off losses and transferring all current to conduction. The voltage drop optimized bridge arm 11 reduces bridge arm conduction losses and improves converter operating efficiency. When hybrid bridge arm 1 is turned off, the turn-off current optimized bridge arm 12 is triggered to turn on first. The turn-off current optimized bridge arm 12 completes zero-voltage soft turn-on and begins to shunt current with the conduction voltage drop optimized bridge arm 11. Then, the conduction voltage drop optimized bridge arm 11 is triggered to turn off. After the conduction voltage drop optimized bridge arm 11 completes zero-voltage soft turn-off, all current of hybrid bridge arm 1 is transferred to the turn-off current optimized bridge arm 12. Finally, the turn-off current optimized bridge arm 12 is triggered to turn off. Its high current turn-off capability improves the converter's operating range. The turn-off current optimized bridge arm 12 has a short conduction time, reducing the current rating requirements of the components.

[0077] This method utilizes the controllable rate of rise of the turn-on current of the turn-off current optimized bridge arm 12 to simplify or even completely eliminate the protection circuit. This method can also reduce the current-carrying time of the turn-off current optimized bridge arm 12 and the current rating requirements of the components.

[0078] In this embodiment, the hybrid bridge arm 1 includes a parallel-connected on-state voltage drop optimized bridge arm 11 and a turn-off current optimized bridge arm 12. The on-state voltage drop of the on-state voltage drop optimized bridge arm 11 is less than that of the turn-off current optimized bridge arm 12, while the current turn-off capability of the turn-off current optimized bridge arm 12 is higher than that of the on-state voltage drop optimized bridge arm 11. The advantageous performance parameters of the on-state voltage drop optimized bridge arm 11 and the turn-off current optimized bridge arm 12 differ. By connecting the low on-state voltage drop optimized bridge arm 11 and the high current turn-off capability turn-off current optimized bridge arm 12 in parallel, a hybrid bridge arm 1 is formed. The hybrid bridge arm 1 forms a half-bridge circuit 2, which constitutes a current source converter. This allows the current source converter to improve its current turn-off capability while reducing the on-state voltage drop, achieving simultaneous optimization of the operating efficiency and operating range of the current source converter, and improving the upper limit of the operating performance constraints of the current source converter.

[0079] In one embodiment, the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 have different structures. Specifically, the different structures of the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 can be due to different numbers of devices included in the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12, or different types of devices included in the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12. The different structures of the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 can also result in different performance parameters, satisfying the requirement 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 that the current turn-off capability of the off-state current optimized bridge arm 12 is higher than that 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, which can 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 requirement 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 turn-off capability of the off-state current optimized bridge arm 12 is higher than the current turn-off 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 turn-off arms. The on-state voltage drop optimized bridge arm 11 being a turn-off arm means that the device included in the on-state voltage drop optimized bridge arm 11 is a turn-off device, such as a turn-off power semiconductor device. Similarly, the off-state current optimized bridge arm 12 being a turn-off arm means that the device included in the off-state current optimized bridge arm 12 is a turn-off device, such as a turn-off power semiconductor device.

[0082] In this embodiment, both the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 are turn-off bridge arms, which can enrich the working modes 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 fully controllable reverse resistance power semiconductor device, which is a fully controllable reverse resistance power semiconductor device with an 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 it is deemed by those skilled in the art to meet the relevant requirements. When the on-state voltage drop is less than the preset on-state voltage drop threshold, it indicates a lower on-state voltage drop. The on-state voltage drop optimization bridge arm 11 includes a first-type fully controllable reverse-resistance power semiconductor device with lower on-state voltage drop, thereby reducing the on-state voltage of the optimized bridge arm 11. The type of the first-type fully controllable reverse-resistance power semiconductor device is not unique, and includes, but is not limited to, reverse-resistance IGCTs (Integrated Gate-Commutated Thyristors), reverse-conducting or asymmetric IGCT series diodes, etc.

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

[0086] Furthermore, in one embodiment, a voltage drop optimization bridge arm 11 includes multiple first-type fully controllable reverse-resistance power semiconductor devices, each connected in series. The number of devices can be two, three, or more, depending on actual requirements. Connecting multiple first-type fully controllable reverse-resistance power semiconductor devices in series can improve the operating voltage and power capacity of the current source converter. It is understood that in other embodiments, a voltage drop optimization bridge arm 11 may also include only one first-type fully controllable reverse-resistance power semiconductor device. This structure avoids the difficulties in implementing a current source converter caused by direct series connection of devices.

[0087] In this embodiment, an optimized on-state voltage drop bridge arm 11 includes multiple first-type fully controlled reverse resistance power semiconductor devices. Each first-type fully controlled reverse resistance power semiconductor device is connected in series, which can improve 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, such as Figure 3As shown, the optimized on-state voltage drop bridge arm 11 also includes a protection circuit 112, which is connected in series with the first type of reverse resistance fully controlled power semiconductor device 111.

[0089] Specifically, the protection circuit serves a protective function. For example, the protection circuit can be a current rise rate protection circuit, connected in series with a first-type reverse-resistance fully controlled power semiconductor device. This circuit limits the current rise rate of the optimized on-state voltage drop bridge arm 11, thus protecting it. The type of protection circuit is not unique; for example, it can include inductive devices such as reactors or controllable saturated reactors.

[0090] In this embodiment, the on-state voltage drop optimized bridge arm 11 also includes a protection circuit. The protection circuit is connected in series with the first type of reverse resistance fully controlled power semiconductor device, which can limit the current rise slope of the on-state voltage drop optimized bridge arm 11 and play the role of 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 fully controllable reverse resistance power semiconductor device, which is a fully controllable reverse resistance 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 values ​​of the preset turn-off current threshold and the preset turn-off loss threshold are not limited, as long as those skilled in the art believe they meet the relevant requirements. A turn-off current greater than the preset turn-off current threshold indicates a large turn-off current. A turn-off loss lower than the preset turn-off loss threshold indicates a low turn-off loss. A large turn-off current or a low turn-off loss indicates strong turn-off capability. The turn-off current optimization bridge arm 12 includes a second type of fully controllable reverse-resistance power semiconductor device with high turn-off capability, to ensure strong turn-off capability of the turn-off current optimization bridge arm 12. The type of the second type of fully controllable reverse-resistance power semiconductor device is not unique, and includes, but is not limited to, reverse-resistance IGBTs (Insulated Gate Bipolar Transistors), asymmetric IGBT series diodes, MOSFET series diodes, emitter-turn-off thyristor series diodes, and diode-assisted turn-off thyristors.

[0093] In this embodiment, the turn-off current optimization bridge arm 12 includes a second type of reverse resistance fully controlled power semiconductor device. The second type of reverse resistance fully controlled power semiconductor device 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, which can make the turn-off capability of the turn-off current optimization bridge arm 12 strong.

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

[0095] The number of devices can be two, three, or more, depending on the actual requirements. Connecting multiple Type II fully controlled reverse-resistance power semiconductor devices in series can improve the operating voltage and power capacity of the current source converter. It is understood that in other embodiments, a turn-off current optimized bridge arm 12 may also include only one turn-off current optimized bridge arm 12 with fully controlled reverse-resistance power semiconductor device. This structure avoids the difficulties in implementing a current source converter caused by direct series connection of devices.

[0096] In this embodiment, a turn-off current optimization bridge arm 12 includes multiple second-type fully controlled reverse resistance power semiconductor devices. Each second-type fully controlled reverse resistance power semiconductor device is connected in series, which can improve 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, such as Figure 4 As shown, the turn-off current optimized bridge arm 12 also includes a protection circuit 122, which is connected in series with the second type of reverse resistance fully controlled power semiconductor device 121.

[0098] Specifically, the protection circuit serves a protective function. For example, the protection circuit can be a current rise rate protection circuit, connected in series with a type II reverse-resistance fully controlled power semiconductor device. This circuit limits the current rise rate of the turn-off current optimization bridge arm 12, thus protecting it. The type of protection circuit is not unique; for example, it can include inductive devices such as reactors or controllable saturated reactors. It is 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 or may not include a protection circuit.

[0099] In this embodiment, the turn-off current optimization bridge arm 12 also includes a protection circuit. The protection circuit is connected in series with the second type of reverse resistance fully controlled power semiconductor device, which can limit the current rise slope of the turn-off current optimization bridge arm 12 and play the role of protecting the turn-off 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-connected on-state voltage drop optimized bridge arm 11 and off-state current optimized bridge arm 12. Specifically, the parallel structure formed by the on-state voltage drop optimized bridge arm 11 and off-state current optimized bridge arm 12 is connected in series with the protection circuit. This can limit the current rise slope of the on-state voltage drop optimized bridge arm 11 and off-state current optimized bridge arm 12, thereby protecting them. The type of protection circuit is not unique; for example, it can include inductive devices such as reactors or controllable saturated reactors. It is understood that when the parallel structure formed by the on-state voltage drop optimized bridge arm 11 and off-state current optimized bridge arm 12 is connected to the protection circuit, the off-state current optimized bridge arm 12 may or may not include the protection circuit, and the on-state voltage drop optimized bridge arm 11 may or may not include the protection circuit, depending on the actual requirements.

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

[0102] Furthermore, the type of protection circuit is not limited. In one embodiment, the protection circuit is a reactor. A reactor can limit the rate of current increase when the current in the circuit rises, thereby limiting the slope of the current rise. 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 it is feasible.

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

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

[0105] Depending on the specific structure of the series voltage equalization circuit, its function varies. For example, when the series voltage equalization circuit includes a dynamic voltage equalization circuit, the dynamic voltage equalization circuit can slow down the rate of voltage change across the power semiconductor devices in the connected on-state voltage drop optimization bridge arm 11 and the off-state current optimization bridge arm 12 during their turn-on and turn-off transients, thereby reducing the dynamic voltage difference between the devices. It is understood that in other embodiments, the series voltage equalization circuit may also include other structures, as long as those skilled in the art believe it is feasible.

[0106] In this embodiment, the half-bridge circuit 2 of the current source converter also includes a series voltage equalization circuit. The series voltage equalization circuit is connected in parallel with the power semiconductor devices in the hybrid bridge arm 1, which can play a role in voltage equalization and improve circuit stability.

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

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

[0109] The static voltage equalization circuit being connected in parallel with power semiconductor devices means that the static voltage equalization circuit can be connected in parallel with the power semiconductor devices in the on-state voltage drop optimization bridge arm 11, and / or, the static voltage equalization circuit can be connected in parallel with the power semiconductor devices in the off-state current optimization bridge arm 12. Further, when the on-state voltage drop optimization bridge arm 11 includes a first type of fully controllable reverse resistance power semiconductor device, and the off-state current optimization bridge arm 12 includes a second type of fully controllable reverse resistance power semiconductor device, the static voltage equalization circuit can be connected in parallel with the first type of fully controllable reverse resistance power semiconductor device in the on-state voltage drop optimization bridge arm 11, and / or, the static voltage equalization circuit can be connected in parallel with the second type of fully controllable reverse resistance power semiconductor device in the off-state current optimization bridge arm 12. The static voltage equalization circuit can balance the leakage current of the power semiconductor devices when the connected power semiconductor devices are in a blocking state, thereby reducing the static voltage difference between the devices and improving the operating performance of the power semiconductor devices.

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

[0111] In this embodiment, the series voltage equalization circuit includes a dynamic voltage equalization circuit, a static voltage equalization circuit, and a voltage clamping circuit, all of which are connected in parallel with the power semiconductor devices. The dynamic voltage equalization circuit can slow down the rate of voltage change across the power semiconductor devices when they are in the turn-on and turn-off transient states, thereby reducing the dynamic voltage difference between the devices. The static voltage equalization circuit can balance the leakage current of the power semiconductor devices when they are in the blocking state, thereby reducing the static voltage difference between the devices and improving their performance. The voltage clamping circuit can limit the voltage of the parallel branches to near the operating threshold, achieving dynamic voltage equalization under extreme operating conditions.

[0112] The structure of the dynamic voltage equalization circuit can also be selected in various ways. For example, in one embodiment, the dynamic voltage equalization circuit includes a dynamic voltage equalization resistor and a dynamic voltage equalization capacitor, and the structure formed by the dynamic voltage equalization resistor and the dynamic voltage equalization capacitor in series is connected in parallel with the power semiconductor device.

[0113] Specifically, when the power semiconductor device connected to the dynamic voltage equalization circuit is in a turn-off transient, the voltage across its terminals rises and charges the dynamic voltage equalization capacitor through the dynamic voltage equalization resistor. The dynamic voltage equalization circuit provides an additional current path, reducing the equivalent input impedance across the power semiconductor device and the rate of voltage rise. When the power semiconductor device connected to the dynamic voltage equalization circuit is in a turn-on transient, the voltage across its terminals drops and discharges the dynamic voltage equalization capacitor through the dynamic voltage equalization resistor. The dynamic voltage equalization circuit provides an additional current source, reducing the equivalent output impedance across the power semiconductor device and the rate of voltage drop.

[0114] In this embodiment, the dynamic voltage equalization circuit includes a dynamic voltage equalization resistor and a dynamic voltage equalization capacitor. The structure formed by the dynamic voltage equalization resistor and the dynamic voltage equalization capacitor connected in series is connected in parallel with the power semiconductor device. When the connected power semiconductor device is in a transient state of being off or on, the dynamic voltage equalization resistor charges or discharges the dynamic voltage equalization capacitor. The dynamic voltage equalization circuit provides an additional current source, reducing the rate of change of the equivalent output impedance and the voltage across the power semiconductor device.

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

[0116] Specifically, when the voltage at the anode port 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 longer generates a voltage drop, thus giving full play to the rapid voltage equalization effect of the dynamic voltage equalization capacitor on high rise rate voltages.

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

[0118] In this embodiment, the dynamic voltage equalization circuit also includes a diode, which is connected in parallel with the dynamic voltage equalization resistor to improve the voltage equalization and limiting effect under high rise rate voltage change conditions.

[0119] In one embodiment, the half-bridge circuit 2 of the current source converter further includes a parallel current sharing circuit, which 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 sharing circuit can be connected in series with the power semiconductor device in the on-state voltage drop optimized bridge arm to increase the upper current limit of the on-state voltage drop optimized bridge arm. Alternatively, the parallel current sharing circuit can be connected in series with the power semiconductor device in the off-state current optimized bridge arm to increase 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 may have a parallel current sharing circuit connected in series, or both the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm may have a parallel current sharing circuit connected in series, depending on the specific requirements.

[0120] In this embodiment, the half-bridge circuit 2 of the current source converter further includes a parallel current sharing circuit, which is connected in series with the power semiconductor devices in the on-state voltage drop optimized bridge arm or the off-state current optimized bridge arm. The parallel current sharing circuit can expand the upper limit of the current in the connected on-state voltage drop optimized bridge arm or the off-state current optimized bridge arm, thereby achieving dynamic current balance between the turn-on process and the on-state state of the power semiconductor devices in the connected on-state voltage drop optimized bridge arm or the off-state current optimized bridge arm.

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

[0122] Specifically, the first winding and the second winding are connected in series with power semiconductor devices on different branches of the on-state voltage drop optimized bridge arm. The on-state voltage drop optimized bridge arm may include multiple parallel sub-bridge arms, each containing a power semiconductor device. Taking the first sub-bridge arm and the second sub-bridge arm as examples, the first sub-bridge arm and the second sub-bridge arm are connected in parallel, and both the first sub-bridge arm and the second sub-bridge arm contain power semiconductor devices. Therefore, the first winding is connected in series with the power semiconductor devices in the first sub-bridge arm, and the second winding is connected in series with the power semiconductor devices in the second sub-bridge arm. When the power semiconductor device connected in series with the first winding turns on faster, a reverse electromotive force will be generated on the second winding. This electromotive force strengthens the positive effect of the voltage across the bridge arm sub-unit, which is composed of the parallel current sharing circuit and the on-state voltage drop optimized bridge arm, on the current rise rate of the power semiconductor device connected in series with the second winding. Conversely, the same applies. Ultimately, this achieves dynamic current balance between the two sets of power semiconductor devices in the two sub-bridge arms of the on-state voltage drop optimized bridge arm during the turn-on process and the on-state.

[0123] Alternatively, the first and second windings can be connected in series with power semiconductor devices on different branches of the turn-off current optimization bridge arm. The turn-off current optimization bridge arm may include multiple parallel sub-bridge arms, each containing a power semiconductor device. Taking the first and second sub-bridge arms as an example, where the first and second sub-bridge arms are connected in parallel and each contains a power semiconductor device, 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 turns on faster, a reverse electromotive force will be generated on the second winding. This electromotive force strengthens the positive effect of the voltage across the bridge arm sub-unit, which is composed of the parallel current sharing circuit and the turn-off 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, this achieves dynamic current balance between the two sets of power semiconductor devices in the turn-on process and conduction state in the two sub-bridge arms of the turn-off current optimization bridge arm.

[0124] In this embodiment, the parallel current sharing circuit includes a first winding and a second winding, which are connected in series with power semiconductor devices on different branches of the on-state voltage drop optimized bridge arm, respectively. Alternatively, the first winding and the second winding are connected in series with power semiconductor devices on different branches of the off-state current optimized bridge arm, respectively; the first winding and the second winding are reverse-coupled. The first winding and the second winding can make the current shared on different branches of the on-state voltage drop optimized bridge arm substantially the same, or make the current shared on different branches of the off-state current optimized bridge arm substantially the same, thereby achieving parallel current sharing between proton-equivalent bridge arms. Here, a proton-equivalent bridge arm refers to different sub-bridge arms within the same on-state voltage drop optimized bridge arm, or different sub-bridge arms within the same off-state current optimized bridge arm.

[0125] In one embodiment, the hybrid bridge arm further includes a controller connected to the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm, for controlling 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. Furthermore, on and off are transient processes, while conduction and blocking are stable states. Switching from conduction to blocking is off, and switching from blocking to conduction is on.

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

[0128] In this 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. Under the control of the controller, the hybrid bridge arm can be in different operating states.

[0129] In one embodiment, a control method for a hybrid bridge arm is provided for controlling 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 turn-off current is controlled to optimize the bridge arm turn-on.

[0131] After the turn-off current optimization bridge arm completes the turn-on and enters the conduction state, the turn-on voltage drop is controlled to optimize the turn-on of the bridge arm;

[0132] After the bridge arm with optimized on-state voltage drop is turned on and enters the on-state, the bridge arm is turned off by optimizing the off-state current.

[0133] as well as,

[0134] When the hybrid arm is turned off, the turn-off current is controlled to optimize the arm turn-on.

[0135] Optimize bridge arm turn-off by controlling conduction voltage drop;

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

[0137] Specifically, when the hybrid bridge arm is turned on, the turn-off current is first triggered to optimize the bridge arm turn-on, the current rise slope is controlled, and the requirements of the converter on the current rise rate protection circuit are reduced.

[0138] After the turn-off current optimized bridge arm completes its turn-on and enters the conduction state, the on-state voltage drop optimized bridge arm is turned on. After the turn-off current optimized bridge arm completes its turn-on and enters the conduction state, the voltage across the hybrid bridge arm is clamped close to zero. At this time, the on-state voltage drop optimized bridge arm is triggered to turn on. The on-state voltage drop optimized bridge arm achieves zero-voltage soft turn-on, reducing turn-on losses and starting to shunt current from the turn-off current optimized bridge arm. Because the on-state voltage drop optimized bridge arm has a lower conduction impedance, the current flowing through the on-state voltage drop optimized bridge arm is greater than that through the turn-off current optimized bridge arm.

[0139] After the on-state voltage drop optimized bridge arm completes its turn-on and enters the conduction state, the turn-off current optimized bridge arm is controlled to turn off. Once the on-state voltage drop optimized bridge arm completes its turn-on and enters the conduction state, the turn-off current optimized bridge arm is triggered to turn off. This achieves zero-voltage soft turn-off, reducing turn-off losses, and transferring all current to the on-state voltage drop optimized bridge arm, thereby reducing bridge arm conduction losses and improving converter operating efficiency.

[0140] When the hybrid bridge arm is turned off, the turn-off current optimized bridge arm is turned on first. The turn-off current optimized bridge arm completes zero-voltage soft turn-on and begins to shunt current with the conduction voltage drop optimized bridge arm.

[0141] Next, the on-state voltage drop optimized bridge arm is turned off. Triggering the on-state voltage drop optimized bridge arm to turn off, after the on-state voltage drop optimized bridge arm completes zero-voltage soft turn-off, all current from the mixed bridge arms is transferred to the turn-off current optimized bridge arm.

[0142] Finally, after the turn-off voltage drop optimized bridge arm completes its turn-off, the turn-off current optimized bridge arm is controlled to turn off. Triggering the turn-off current optimized bridge arm utilizes its high current turn-off capability to improve the converter's operating range. The turn-off current optimized bridge arm has a short turn-on time, reducing the current rating requirements for its components.

[0143] This method utilizes the controllable rise rate of the turn-on current of the turn-off current optimized bridge arm to simplify or even completely eliminate the protection circuit. This method can also reduce the current-carrying time of the turn-off current optimized bridge arm and the current rating requirements of the components.

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

[0145] When the hybrid bridge arm is turned on, the turn-off current is controlled to optimize the bridge arm turn-on.

[0146] After the turn-off current optimization bridge arm completes the turn-on and enters the conduction state, the conduction voltage drop optimization bridge arm is turned on, and the turn-off current optimization bridge arm and the conduction voltage drop optimization bridge arm are simultaneously energized.

[0147] as well as,

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

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

[0150] Specifically, when the hybrid bridge arm is turned on, the turn-off current is controlled to optimize the bridge arm turn-on. When the hybrid bridge arm is turned on, the turn-off current-optimized bridge arm turn-on is triggered first, and the current rise rate is controlled, reducing the requirements of the converter on the current rise rate protection circuit.

[0151] After the turn-off current optimized bridge arm completes its turn-on and enters the conduction state, the conduction voltage drop optimized bridge arm is turned on, and both the turn-off current optimized bridge arm and the conduction voltage drop optimized bridge arm conduct current simultaneously. After the turn-off current optimized bridge arm completes its turn-on and enters the conduction state, the voltage across the hybrid bridge arm is clamped close to zero. At this time, the conduction voltage drop optimized bridge arm is triggered to turn on, achieving zero-voltage soft turn-on, reducing turn-on losses, and starting to shunt current from the turn-off current optimized bridge arm. Because the conduction impedance of the conduction voltage drop optimized bridge arm is lower, the current flowing through the conduction voltage drop optimized bridge arm is greater than that through the turn-off current optimized bridge arm. The simultaneous conduction of current through the hybrid bridge arms further reduces bridge arm conduction losses and improves converter operating efficiency.

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

[0153] Finally, after the on-state voltage drop optimized bridge arm completes turn-off, the turn-off current optimized bridge arm is controlled to turn off. Triggering the turn-off of the turn-off current optimized bridge arm utilizes its high current turn-off capability to improve the converter's operating range. The amplitude of the on-state current of the turn-off current optimized bridge arm is small, partially reducing the current rating requirements of the constituent components.

[0154] This method simplifies the protection circuit by utilizing the controllable rate of rise of the turn-on current of the turn-off current optimized bridge arm, and partially reduces the on-state current of the turn-off current optimized bridge arm and the current rating requirements of the constituent devices.

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

[0156] When the hybrid arm is turned on, the on-state voltage drop is controlled to optimize the arm turn-on.

[0157] as well as,

[0158] When the hybrid arm is turned off, the turn-off current is controlled to optimize the arm turn-on.

[0159] After the turn-off current optimization bridge arm completes the turn-on and enters the conduction state, the turn-off voltage drop is controlled to optimize the turn-off of the bridge arm.

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

[0161] Specifically, when the hybrid bridge arm is turned on, the on-state voltage drop is controlled to optimize the bridge arm turn-on. When the hybrid bridge arm is turned on, the on-state voltage drop optimized bridge arm is triggered first. The protection circuit limits the current rise slope. After the on-state voltage drop optimized bridge arm enters the conduction state, it bears the full current. The low on-state voltage drop characteristic can reduce conduction losses and improve the converter operating efficiency.

[0162] When the hybrid bridge arm is turned off, the turn-off current optimized bridge arm is turned on first. After the turn-off current optimized bridge arm enters the conducting state, it is briefly shunt with the conducting voltage drop optimized bridge arm.

[0163] Subsequently, after the turn-off current optimized bridge arm completes its turn-on and enters the conduction state, the turn-off voltage drop optimized bridge arm is controlled to turn off. This triggers the turn-off of the turn-off voltage drop optimized bridge arm. After the turn-off voltage drop optimized bridge arm completes zero-voltage soft turn-off, all current from the mixed bridge arms is transferred to the turn-off current optimized bridge arm.

[0164] Finally, after the turn-off voltage drop optimized bridge arm completes its turn-off, the turn-off current optimized bridge arm is controlled to turn off. Triggering the turn-off of the turn-off current optimized bridge arm utilizes its high-current turn-off capability to improve the converter's operating range. The turn-off current optimized bridge arm has the shortest turn-on time, minimizing the current rating requirements on the constituent components.

[0165] This approach minimizes the current conduction time of the turn-off current-optimized bridge arm and the current rating requirements of the constituent devices, while eliminating the requirement for a controllable turn-on current rise slope for the turn-off current-optimized bridge arm.

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

[0167] When the hybrid arm is turned on, the on-state voltage drop is controlled to optimize the arm turn-on.

[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 turned on, and the off-state current optimization bridge arm and the on-state voltage drop optimization bridge arm are simultaneously flowing.

[0169] as well as,

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

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

[0172] Specifically, when the hybrid bridge arm is turned on, the on-state voltage drop is controlled to optimize the bridge arm's turn-on. When the hybrid bridge arm is turned on, the on-state voltage drop optimized bridge arm is triggered first, and the protection circuit limits the current rise rate. After the on-state voltage drop optimized bridge arm enters the conduction state, the hybrid bridge arm has the characteristic of low conduction loss.

[0173] Subsequently, after the on-state voltage drop optimized bridge arm completes its turn-on and enters the conduction state, the turn-off current optimized bridge arm is turned on, and both the turn-off current optimized bridge arm and the on-state voltage drop optimized bridge arm conduct current simultaneously. This triggers the turn-off current optimized bridge arm to complete zero-voltage soft-start and begins to shunt current from the turn-off current optimized bridge arm. Because the on-state voltage drop optimized bridge arm has a lower on-resistance, the current flowing through it is greater than that through the turn-off current optimized bridge arm. The simultaneous conduction of current through both bridge arms further reduces bridge arm conduction losses and improves converter operating efficiency.

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

[0175] Finally, after the on-state voltage drop optimized bridge arm completes turn-off, the turn-off current optimized bridge arm is turned off. Triggering the turn-off current optimized bridge arm utilizes its high-current turn-off capability to extend the converter's operating range.

[0176] This approach minimizes the on-state voltage drop of the hybrid bridge arm, maximizing converter operating efficiency. Similarly, this approach eliminates the requirement for a controllable on-state current rise rate for the turn-off current-optimized bridge arm.

[0177] In one embodiment, a half-bridge circuit is provided, including an upper bridge arm and a lower bridge arm connected in series, wherein at least one of the upper and lower bridge arms is a hybrid bridge arm as described above. That is, as... Figure 2 As shown, both the upper and lower bridge arms 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 terminal of the upper and lower bridge arms serves 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, including a half-bridge circuit 2 as described 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, there are three half-bridge circuits 2 connected in parallel. The three half-bridge circuits 2 connected in parallel 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.

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

[0181] When the current source converter is operating in steady state, the current amplitude of the smoothing reactor 3 is approximately constant. When the upper arm of the half-bridge circuit 2 is turned on and the lower 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 arm of the half-bridge circuit 2 is turned on and the upper 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 both the upper and lower arms of the half-bridge circuit 2 are turned on, the smoothing reactor 3 continues to flow 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 switching states of the upper and lower bridge arms remain unchanged, the injected current generates conduction losses across the on-state voltage drops of the upper and lower bridge arms. When the switching states of the upper and lower bridge arms switch, the devices actively turn off to complete the current transfer. Therefore, the on-state voltage drop and turn-off capability of the upper and lower bridge arms are key parameters. A lower on-state voltage drop can improve the efficiency of the current source converter, reduce heat dissipation power requirements and operating costs; a higher turn-off capability can extend the operating range of the current source converter, improve fault tolerance and operational reliability. The upper and lower bridge arms have four states: on, off, conduction, and blocking. On and off are transient processes, while conduction and blocking are steady states. Switching from conduction to blocking is off, and switching from blocking to conduction is on.

[0183] To better understand the above embodiments, a detailed explanation is provided below with reference to a specific embodiment. In one embodiment, based on the technical idea of ​​reducing the on-state voltage drop of a current-source converter bridge arm while improving its current-turn-off capability, this application proposes a hybrid bridge arm and its control method, a half-bridge circuit, and a current-source converter. Specifically, a bridge arm with low on-state voltage drop and a bridge arm with high current-turn-off capability are connected in parallel to form a hybrid bridge arm, which constitutes a current-source converter. The bridge arm with low on-state voltage drop and the bridge arm with high current-turn-off capability use power semiconductor devices with different advantageous performance parameters.

[0184] An embodiment of a current source converter composed of hybrid bridge arms according to this application is shown in Figure 2. The hybrid bridge arms 1 are connected in series to form a half-bridge circuit, and the three half-bridge circuits are connected in parallel to form a current source converter. The hybrid bridge arms 1 are composed of a set of on-state voltage drop optimized bridge arms 11 and a set of off-state current optimized bridge arms 12 connected in parallel.

[0185] The topology of the optimized on-state voltage drop bridge arm 11 is shown in Figure 3. It consists of a fully controllable reverse-resistance power semiconductor device 111 with low on-state voltage drop and a protection circuit 112 connected in series. The number of series stages is ≥1, including but not limited to reverse-resistance IGCT and reverse-conducting or asymmetric IGCT series diodes.

[0186] The topology of the turn-off current optimized bridge arm 12 is shown in Figure 4. It consists of a reverse-resistance fully controlled power semiconductor device 121 with large turn-off current or low turn-off loss and a protection circuit 122 connected in series. 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 contain series voltage equalization and / or parallel current equalization circuits of unspecified form. Their power semiconductor devices 111 and 112 can be connected in parallel to increase the maximum allowable current of the bridge arm, with a parallel number ≥ 1.

[0188] The protection circuit is generally a current rise rate protection circuit, which can be shown in Figures 3 and 4 as protection circuits 111 and 112, respectively, connected in series in the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12. Alternatively, as shown in Figure 5, it can be centralized as protection circuit 13 directly connected in series with the hybrid bridge arm. When protection circuit 13 is directly connected in series with the hybrid bridge arm, the protection circuits in the on-state voltage drop optimized bridge arm 11 and the off-state current optimized bridge arm 12 can be retained as shown in Figures 3 and 4, or removed as shown in Figures 6 and 7. The following explanation is based on several detailed embodiments:

[0189] Example 1:

[0190] One operating mode of the current source converter composed of hybrid bridge arms in this application is as follows:

[0191] a) When hybrid bridge arm 1 is turned on, the turn-off current optimization bridge arm 12 is triggered first, the current rise slope is controlled, and the converter's requirements for the current rise rate protection circuit are reduced.

[0192] b) After the turn-off current optimized bridge arm 12 is turned on and enters the conduction state, the voltage across the hybrid bridge arm 1 is clamped to near zero. At this time, the conduction voltage drop optimized bridge arm 11 is triggered to turn on. The conduction voltage drop optimized bridge arm 11 achieves zero-voltage soft turn-on, reduces turn-on losses and begins to shunt current with the turn-off current optimized bridge arm 12. Since the conduction impedance of the conduction voltage drop optimized bridge arm 11 is lower, the current flowing through the conduction voltage drop optimized bridge arm 11 is greater than that through the turn-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. The off-state current optimized bridge arm 12 achieves zero-voltage soft turn-off, reduces turn-off loss and transfers all current to the on-state voltage drop optimized bridge arm 11, thereby reducing bridge arm conduction loss and improving converter operating efficiency.

[0194] d) When hybrid bridge arm 1 is turned off, the turn-off current optimized bridge arm 12 is turned on first. The turn-off current optimized bridge arm 12 completes zero-voltage soft turn-on and begins to shunt with the on-state voltage drop optimized bridge arm 11.

[0195] e) After that, the on-state voltage drop optimized bridge arm 11 is turned off. After the on-state voltage drop optimized bridge arm 11 completes the zero-voltage soft turn-off, all the current of the mixed bridge arm 1 is transferred to the turn-off current optimized bridge arm 12.

[0196] f) Finally, the turn-off current optimization bridge arm 12 is turned off, which utilizes its high current turn-off capability to improve the operating range of the converter. The turn-off current optimization bridge arm 12 has a short conduction time, which reduces the current level requirements of the components.

[0197] At this point, the preferred type of device constituting the turn-off current optimization bridge arm 12 is a fully controllable reverse-resistance power semiconductor device with a controllable current rise rate, including but not limited to reverse-resistance IGBTs, asymmetric IGBT series diodes, and MOSFET series diodes. This method utilizes the controllable turn-on current rise rate of the turn-off current optimization bridge arm 12 to simplify or even completely eliminate the protection circuit. The topologies of hybrid bridge arm 1, on-state voltage drop optimization bridge arm 11, and turn-off current optimization bridge arm 12 are shown in Figure 2, respectively. Figure 6 As shown in Figure 7. Furthermore, this method can reduce the turn-off current, optimize the current-carrying time of bridge arm 12, and lower the current rating requirements of the constituent devices.

[0198] Example 2:

[0199] One operating mode of the current source converter composed of hybrid bridge arms in this application is as follows:

[0200] a) When hybrid bridge arm 1 is turned on, the turn-off current optimization bridge arm 12 is triggered first, the current rise slope is controlled, and the converter's requirements for the current rise rate protection circuit are reduced.

[0201] b) After the turn-off current optimized bridge arm 12 is turned on and enters the conduction state, the voltage across the hybrid bridge arm 1 is clamped close to zero. At this time, the conduction voltage drop optimized bridge arm 11 is triggered to turn on. The conduction voltage drop optimized bridge arm 11 achieves zero-voltage soft turn-on, reduces turn-on losses, and begins to shunt current with the turn-off current optimized bridge arm 12. Since the conduction impedance of the conduction voltage drop optimized bridge arm 11 is lower, the current flowing through the conduction voltage drop optimized bridge arm 11 is more than that through the turn-off current optimized bridge arm 12. The hybrid bridge arms carry current at the same time, further reducing bridge arm conduction losses and improving converter operating efficiency.

[0202] c) When 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 zero-voltage soft turn-off, all the current of hybrid bridge arm 1 is transferred to the turn-off current optimized bridge arm 12.

[0203] d) Finally, the turn-off current optimization bridge arm 12 is turned off, which utilizes its high current turn-off capability to improve the operating range of the converter. The turn-off current optimization bridge arm 12 has a small conduction current amplitude, which partially reduces the current rating requirements of the components.

[0204] This method simplifies the protection circuit by utilizing the controllable rate of rise of the turn-on current of the turn-off current-optimized bridge arm 12, and partially reduces the on-state current of the turn-off current-optimized bridge arm 12 and the current rating requirements of its constituent devices. Similarly, this method simplifies or even completely eliminates the protection circuit by utilizing the controllable rate of rise of the turn-on current of the turn-off current-optimized bridge arm 12. The topologies of the hybrid bridge arm 1, the on-state voltage drop optimized bridge arm 11, and the turn-off current-optimized bridge arm 12 are shown in Figures 2, 6, and 7, respectively. Furthermore, this method can also reduce the current-carrying time of the turn-off current-optimized bridge arm 12 and the current rating requirements of its constituent devices.

[0205] Example 3:

[0206] One operating mode of the current source converter composed of hybrid bridge arms in this application is as follows:

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

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

[0209] c) Then the on-state voltage drop optimized bridge arm 11 is turned off. After the on-state voltage drop optimized bridge arm 11 completes zero-voltage soft turn-off, all the current of the mixed bridge arm 1 is transferred to the turn-off current optimized bridge arm 12.

[0210] d) Finally, the turn-off current optimization bridge arm 12 is turned off, which utilizes its high current turn-off capability to improve the operating range of the converter. The turn-off current optimization bridge arm 12 has the shortest conduction time, which minimizes the current level requirements of the components.

[0211] This approach minimizes the current-on time of the turn-off current optimization bridge arm 12 and the current rating requirements of its components, while eliminating the need for a controllable turn-on current rise slope for the turn-off current optimization bridge arm 12. Optional device types are not limited to reverse-resistance IGBTs, asymmetric IGBTs in series with diodes, and MOSFETs in series with diodes; they can also be extended to emitter-turn-off thyristors in series with diodes and diode-assisted turn-off thyristors. A specific implementation of the protection circuit is shown in Figure 8, which uses a saturated reactor that can be centrally or distributed.

[0212] Example 4:

[0213] One operating mode of the current source converter composed of hybrid bridge arms in this application is as follows:

[0214] a) When hybrid bridge arm 1 is turned on, it first triggers the turn-on of bridge arm 11 with optimized on-state voltage drop. The protection circuit limits the current rise slope. After bridge arm 11 with optimized on-state voltage drop enters the conduction state, hybrid bridge arm 1 has the characteristic of low conduction loss.

[0215] b) After that, the turn-off current optimization bridge arm 12 is triggered to complete zero-voltage soft turn-on and begins to shunt current with the turn-off current optimization bridge arm 12. Since the conduction impedance of the conduction voltage drop optimization bridge arm 11 is lower, the current flowing through the conduction voltage drop optimization bridge arm 11 is more than that of the turn-off current optimization bridge arm 12. The mixed bridge arms carry current at the same time, further reducing the bridge arm conduction loss and improving the converter operating efficiency.

[0216] c) When 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 zero-voltage soft turn-off, all the current of hybrid bridge arm 1 is transferred to the turn-off current optimized bridge arm 12.

[0217] d) Finally, the turn-off current is optimized to turn off bridge arm 12, thereby improving the converter's operating range by utilizing its high-current turn-off capability.

[0218] This approach maximizes the low on-state voltage drop current-carrying time and thus maximizes converter operating efficiency. Similarly, this approach eliminates the requirement for controllable turn-off current rise slope in the optimized bridge arm 12. The types of devices that can be selected are not limited to reverse-resistance IGBTs, asymmetric IGBTs in series with diodes, or MOSFETs in series with diodes; it can also be extended to emitter-turn-off thyristors in series with diodes and diode-assisted turn-off thyristors. A specific implementation of the protection circuit is shown in Figure 8, which uses a saturated reactor that can be centrally or distributed.

[0219] Example 5:

[0220] As shown in Figure 9, one implementation method of the current source converter of this application for optimizing the on-state voltage drop of bridge arm 11 and optimizing the off-state current of bridge arm 12 is formed by power semiconductor devices and series voltage equalization circuits in parallel to form bridge arm sub-units 111 and 112. The series voltage equalization circuit consists of a dynamic voltage equalization circuit formed by dynamic voltage equalization resistor 1111 and dynamic voltage equalization capacitor 11112 in series, a static voltage equalization circuit composed of static voltage equalization resistor 1113, and a voltage clamping circuit implemented by surge arrester 1114.

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

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

[0223] In the voltage clamping circuit, the equivalent impedance of the surge arrester 1114 decreases as the voltage across it increases. This is used to limit the further rise of the voltage across the overvoltage power semiconductor device during the turn-off transient, forcing other devices in the series branch to withstand the voltage, thereby making the voltages across each device approach each other.

[0224] Example 6:

[0225] As shown in Figure 10, one implementation method of the current source converter of this application for optimizing the on-state voltage drop of bridge arm 11 and optimizing the off-state current of bridge arm 12 is formed by power semiconductor devices and series voltage equalization circuits in parallel to form bridge arm sub-units 111 and 112. The series voltage equalization circuit consists of a dynamic voltage equalization circuit formed by a dynamic voltage equalization resistor 1111 and a diode 1115 connected in parallel and then connected 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 surge arrester 1114.

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

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

[0228] In the voltage clamping circuit, the equivalent impedance of the surge arrester 1114 decreases as the voltage across it increases. This is used to limit the further rise of the voltage across the overvoltage power semiconductor device during the turn-off transient, forcing other devices in the series branch to withstand the voltage, thereby making the voltages across each device approach each other.

[0229] Example 7:

[0230] As shown in Figure 11, one implementation method of the current source converter of this application is as follows: two sets of power semiconductor devices in the same on-state voltage drop optimization bridge arm or two sets of power semiconductor devices in the same off-state current optimization bridge arm are connected in series with windings 1116 and 1117 and then connected in parallel to form bridge arm sub-units 111 and 112, respectively. Windings 1116 and 1117 are reverse coupled.

[0231] When the power semiconductor device connected in series with winding 1116 turns on faster, a reverse electromotive force will be generated in winding 1117. This electromotive force strengthens the positive effect of the voltage across 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 dynamic current balance between the two sets of power semiconductor devices during the turn-on process and the conduction state.

[0232] The half-bridge circuit and current source converter provided in this application can increase the turn-off current while reducing the on-state 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, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0234] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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 embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A hybrid bridge arm, characterized in that, Applied to current source converters; The hybrid bridge arm includes a parallel on-state voltage drop optimized bridge arm and a turn-off current optimized bridge arm. The on-state voltage drop of the on-state voltage drop optimized bridge arm is less than the on-state 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 that of the on-state voltage drop optimized bridge arm.

2. The hybrid bridge arm according to claim 1, characterized in that, The structures of the bridge arm with optimized on-state voltage drop and the bridge arm with optimized off-state current are different.

3. The hybrid bridge arm according to claim 1, characterized in that, Both the on-state voltage drop optimized bridge arm and the off-state current optimized bridge arm are turn-off bridge arms.

4. The hybrid bridge arm according to claim 1, characterized in that, The optimized on-state voltage drop bridge arm includes a first type of fully controllable reverse resistance power semiconductor device, which is a fully controllable reverse resistance 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 aforementioned optimized on-state voltage drop bridge arms includes multiple first-type fully controllable reverse resistance power semiconductor devices, with each first-type fully controllable reverse resistance power semiconductor device connected in series.

6. The hybrid bridge arm according to claim 4, characterized in that, The optimized on-state voltage drop bridge arm also includes a protection circuit, which 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 turn-off current optimization bridge arm includes a second type of fully controllable reverse resistance power semiconductor device, which is a fully controllable reverse resistance 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.

8. The hybrid bridge arm according to claim 7, characterized in that, One of the aforementioned turn-off current optimized bridge arms includes multiple second-type fully controllable reverse-resistance power semiconductor devices, each of which is connected in series.

9. The hybrid bridge arm according to claim 7, characterized in that, The turn-off current optimized bridge arm also includes a protection circuit, which is connected in series with the second type of 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-state voltage drop optimized bridge arm and the off-state current optimized 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 equalization circuit, which is connected in parallel with the power semiconductor devices in the hybrid bridge arm.

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

15. The hybrid bridge arm according to claim 14, characterized in that, The dynamic voltage equalization circuit includes a dynamic voltage equalization resistor and a dynamic voltage equalization capacitor, and the structure formed by the dynamic voltage equalization resistor and the dynamic voltage equalization capacitor 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 equalization circuit also includes a diode, which is connected in parallel with the dynamic voltage equalization 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 optimized bridge arm or the off-state current optimized bridge arm.

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

19. A control method for a hybrid bridge arm, characterized in that, The method includes: When the hybrid bridge arm is turned on, the turn-off current is controlled to optimize the bridge arm turn-on. After the turn-off current optimized bridge arm completes the turn-on and enters the conduction state, the conduction voltage drop optimized bridge arm is turned on. After the optimized on-voltage drop bridge arm completes the on-state and enters the on-state, the optimized off-current bridge arm is controlled to turn off. as well as, When the hybrid bridge arm is turned off, the turn-off current is controlled to optimize the bridge arm turn-on; Controlling the on-state voltage drop optimizes bridge arm turn-off; After the optimized on-voltage drop bridge arm completes the turn-off, the optimized turn-off current bridge arm is controlled to turn off.

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

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

22. The method according to claim 19, characterized in that, The method further includes: When the hybrid bridge arm is turned on, the on-state voltage drop is controlled to optimize the bridge arm turn-on; 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 turned on, and the off-state current optimized bridge arm and the on-state voltage drop optimized bridge arm are simultaneously flowing. as well as, When the hybrid bridge arm is turned off, the on-state voltage drop is controlled to optimize the bridge arm turn-off; After the optimized on-voltage drop bridge arm completes the turn-off, the optimized turn-off current bridge arm is controlled to turn off.

23. A half-bridge circuit, characterized in that, It includes 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 in any one of claims 1-17.

24. A current source converter, characterized in that, Includes the half-bridge circuit as described in claim 23.

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

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