Lightweight high-voltage high-capacity ac-dc converter based on thyristors and cascaded module chains

Abstract

The application provides a light high-voltage large-capacity AC-DC converter based on thyristors and cascaded module chains, and belongs to the technical field of large-capacity AC-DC converter topologies.The application comprises three phase units with the same structure, which are connected to a common DC bus after being cascaded at the DC side and are connected to an AC power grid through open-winding transformers at the AC side;each phase unit comprises a commutating valve and a cascaded module chain, and the commutating valve is connected in parallel with the cascaded module chain;each commutating valve adopts an H-bridge topology structure and comprises two parallel-connected bridge arms, and each bridge arm is composed of two thyristor valve units and a commutation inductor in series;each cascaded module chain is composed of a plurality of half-bridge sub-modules and full-bridge sub-modules in series, and the number of the half-bridge sub-modules is greater than that of the full-bridge sub-modules.When the application is in normal operation, high-voltage DC voltage is obtained through the cascading of the three-phase module chains, the number of sub-modules can be greatly reduced, the energy fluctuation of the sub-modules is reduced, and thus the capacitance value is reduced.

Description

Technical Field

[0001] This invention relates to a lightweight, high-voltage, high-capacity AC / DC converter based on thyristors and cascaded module chains, belonging to the field of high-capacity AC / DC converter topology technology. Background Technology

[0002] With the development of high-voltage direct current (HVDC) transmission, renewable energy grid integration, large-capacity long-distance power transmission, and multi-terminal DC grids, HVDC transmission systems based on voltage source converters are increasingly widely used in power systems. Modular multilevel converters, with their excellent output waveform, high-voltage easy expansion, and modular design, have become an important development direction for high-voltage, high-capacity voltage source converters.

[0003] However, commonly used modular multilevel converter topologies suffer from problems such as large number of modules, high capacitor values, and numerous power devices, resulting in large size, heavy weight, and high losses, which hinders the lightweight design of equipment. Furthermore, the large size and weight increase the difficulty of installation, transportation, maintenance, and engineering applications, making it unsuitable for scenarios such as offshore wind power and flexible DC transmission. Lightweight, high-voltage, high-capacity AC / DC converters based on thyristors and cascaded module chains show promising application prospects in addressing these issues. Summary of the Invention

[0004] The purpose of this invention is to solve the commutation problem caused by the non-self-turn-off capability of thyristors in the prior art, and to provide a lightweight, high-voltage, high-capacity AC / DC converter based on thyristors and a cascaded module chain. This invention uses anti-parallel thyristors as commutation valve devices and configures a novel high-capacity AC / DC converter topology with a small number of full-bridge sub-modules and a large number of half-bridge sub-modules in the cascaded module chain. The main inventive features of this invention are: using thyristors to improve current and voltage withstand capabilities, achieving reliable turn-off in conjunction with the hybrid full- and half-bridge cascaded module chain, and reducing capacitor usage to achieve a lightweight converter.

[0005] During normal operation, the three-phase module chain cascaded to obtain a high-voltage DC voltage, which can significantly reduce the number of sub-modules, reduce sub-module energy fluctuations, and thus reduce capacitor values. Thyristors handle AC voltage and current commutation, providing a consistently positive half-wave voltage to the cascaded module chain. Therefore, the cascaded module chain mainly uses half-bridge sub-modules, reducing the number of power devices. Simultaneously, the high voltage withstand capability, low on-resistance, and low loss of thyristors reduce commutation conduction losses and heat dissipation pressure. Furthermore, thyristor series technology is mature and reliable, with numerous engineering applications. A small number of full-bridge sub-modules provide reverse commutation voltage when the thyristor valve is turned off, driving the thyristor current to drop to zero, and applying a reverse voltage for a period of time ensures reliable thyristor turn-off. The high-capacity AC / DC converter topology proposed in this invention combines advantages such as fewer modules, lower capacitor values, smaller size and weight, lower cost, lower heat dissipation pressure, and lightweight design.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A lightweight high-voltage high-capacity AC / DC converter based on thyristors and cascaded module chains includes three phase units with identical structures. The three phase units are cascaded on the DC side and connected to a common DC bus. On the AC side, they are connected to the AC power grid through an open-winding transformer.

[0008] Each phase unit includes: a commutation valve and a cascade module chain, wherein the two DC terminals of the commutation valve are connected in parallel to the two sides of the cascade module chain, and the AC terminal of the commutation valve is connected to an open-winding transformer.

[0009] Each of the commutation valves adopts an H-bridge topology, including two bridge arms. Each bridge arm consists of two thyristor valve units and a commutation inductor connected in series. The two bridge arms are connected in parallel, and the midpoints of the two bridge arms are respectively connected to an open-winding transformer.

[0010] Each of the cascaded module chains consists of several sub-modules connected in series. The sub-modules include half-bridge sub-modules and full-bridge sub-modules, with the number of half-bridge sub-modules being greater than the number of full-bridge sub-modules.

[0011] Preferably, each of the thyristor valve units includes a set of anti-parallel thyristors connected in series.

[0012] Preferably, each of the directional valves includes a thyristor valve unit. and commutation inductor and ; Thyristor valve unit and and commutation inductor Comprising the first bridge arm, thyristor valve unit and and commutation inductor Forming the second bridge arm,

[0013] commutation inductor One end is connected to the commutation inductor One end is connected to the commutator inductor. The other end is connected to the thyristor valve unit. One end is connected to the thyristor valve unit. The other end is connected to the thyristor valve unit. One end is connected to the thyristor valve unit. With thyristor valve unit The connection point is at the midpoint of the first bridge arm, and the commutation inductor... The other end is connected to the thyristor valve unit. One end is connected to the thyristor valve unit. The other end is connected to the thyristor valve unit. One end is connected to the thyristor valve unit. With thyristor valve unit The connection point is at the midpoint of the second bridge arm, thyristor valve unit. The other end is connected to the thyristor valve unit. The other end is connected, and the midpoints of the first and second bridge arms are respectively connected to the open-winding transformer.

[0014] Preferably, each of the cascaded module chains includes One and a half bridge submodules and There are 1 full-bridge sub-modules, and the module quantity relationship is as follows: , and All are integers greater than or equal to 1.

[0015] Preferably, the output state of the half-bridge submodule is 0 or ,in This represents the capacitor voltage of a single submodule; the output state of the full-bridge submodule is 0. or .

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] This invention employs a topology of three-phase cascaded module chains cascaded on the DC side, which not only reduces the total number of sub-modules, but also ensures that the cascaded module chains only provide a positive half-wave voltage during normal operation, resulting in small energy fluctuations in the sub-modules. This greatly reduces the demand for sub-module capacitor values, further compressing the physical volume. The overall device is smaller in size and weight, which can effectively reduce manufacturing, transportation, installation, and maintenance costs.

[0018] The directional valve of this invention uses anti-parallel thyristors switching at power frequency (50Hz) and does not handle high-frequency PWM modulation. This invention uses thyristors as the switching devices for the directional valve, which have the advantages of high voltage resistance, strong current carrying capacity, low conduction loss, and mature and reliable series connection technology. Compared to solutions using fully controlled devices (such as IGBTs or IGCTs), this topology significantly reduces switching losses, conduction losses, and heat dissipation requirements, thus improving the overall system efficiency and reliability.

[0019] This invention configures only a small number of full-bridge sub-modules in the cascaded module chain, while most modules still adopt a half-bridge structure, eliminating the need for complex parallel auxiliary commutation branches. The full-bridge sub-modules only output reverse commutation voltage in the commutation section to establish reverse recovery conditions, ensuring reliable thyristor turn-off. Simultaneously, it minimizes the number of fully controllable devices used, avoiding the significant cost increases and control complexity issues associated with using only full-bridge sub-modules.

[0020] Therefore, the present invention has significant advantages in reducing the number of modules, capacitor configuration, cost, size and weight, heat dissipation pressure and device lightweighting, and is suitable for high-voltage and high-capacity AC / DC conversion scenarios and flexible AC interconnection and direct-connected energy storage scenarios. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the circuit topology of the lightweight high-voltage high-capacity AC / DC converter based on thyristors and cascaded module chains of the present invention.

[0022] Figure 2 This is a schematic diagram of the reversing valve bridge arm switch of the present invention.

[0023] Figure 3 This is a structural diagram of the cascaded module chain full-bridge and half-bridge of the present invention.

[0024] Figure 4 This is a schematic diagram of the trigger signal for the a-phase thyristor to turn on according to the present invention.

[0025] Figure 5 This is a schematic diagram of the power grid phase voltage according to the present invention.

[0026] Figure 6 This is a schematic diagram of the AC side current (operating at unity power factor) of the present invention.

[0027] Figure 7 This is a schematic diagram of the DC bus voltage and the output voltage of the three-phase cascaded module chain of the present invention.

[0028] Figure 8 This is a schematic diagram of the DC bus current of the present invention.

[0029] Figure 9 This is a schematic diagram of the chain current of the a-phase cascaded module of the present invention.

[0030] Figure 10 The reversing valve of the present invention A schematic diagram of the voltage across the two ends.

[0031] Figure 11 The reversing valve of the present invention A schematic diagram of the voltage across the two ends.

[0032] Figure 12 The flow-through reversing valve of the present invention A schematic diagram of the current.

[0033] Figure 13 The flow-through reversing valve of the present invention A schematic diagram of the current.

[0034] Figure 14 The above is a simulation waveform diagram of the power grid phase voltage of the present invention.

[0035] Figure 15 The AC input current simulation waveform diagram is shown in the present invention.

[0036] Figure 16 The above are simulation waveforms of the DC-side voltage and the three-phase module chain voltage of the present invention.

[0037] Figure 17 The waveform diagram of the three-phase module chain current simulation of the present invention is shown. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the accompanying drawings: This embodiment is implemented under the premise of the technical solution of the present invention, and detailed implementation methods are given, but the protection scope of the present invention is not limited to the following embodiments.

[0039] like Figure 1 and Figure 2 As shown, the lightweight high-voltage, high-capacity AC / DC converter (hereinafter referred to as the MCC converter) based on thyristors and cascaded module chains involved in this embodiment includes three phase units with identical three-phase structures, namely phase a, phase b, and phase c. Each phase unit includes a commutation valve and a cascaded module chain. The key feature is that each commutation valve also includes two commutation inductors connected in series with half of the bridge arm, and the cascaded module chain is formed by cascading half-bridge sub-modules and full-bridge sub-modules.

[0040] The three phase units are cascaded on the DC side and connected to a common DC bus, and on the AC side they are connected to the AC power grid through an open-winding transformer.

[0041] The above-mentioned unit structure mainly consists of four switches of the directional valve, each using an anti-parallel thyristor valve unit. The cascaded module chain unit is composed of a majority of half-bridge sub-modules and a small number of full-bridge sub-modules cascaded together. It is used to provide the rectified envelope voltage required by the AC side during normal operation. During commutation, the full-bridge sub-module outputs an additional commutation voltage and applies reverse voltage to the thyristor to be turned off, so as to realize the commutation of current between different thyristors and at the same time realize the reliable turn-off of the thyristors.

[0042] Topology Figure 1 As shown, taking phase a as an example, the directional valve adopts an H-bridge topology and contains four thyristor valve units. Each thyristor valve unit consists of a set of series-connected anti-parallel thyristors to meet the withstand voltage requirements of high-voltage, high-power applications, while also enabling the directional valve to carry bidirectional current. Phase B and phase C each include a thyristor valve unit. and thyristor valve unit .

[0043] The gate trigger signals for each valve position are denoted as follows: , , The trigger signal diagram for phase a is shown below. Figure 4 As shown The directional valve unit only performs polarity reversal and main current conduction functions during most power frequency cycles, and does not perform high-frequency PWM modulation functions, thereby reducing the switching frequency and switching losses of the directional valve.

[0044] A small-value commutation inductor is connected in series in each of the left and right half-bridge arms of the commutation valve in each phase, as shown in the detailed diagram below. Figure 2 As shown. Taking phase a as an example, the commutation inductance on the left side is denoted as... The commutation inductor on the right side is denoted as The commutation inductors on the left and right sides corresponding to phases b and c are respectively denoted as... .

[0045] The function of the commutation inductor includes: limiting the rate of change of current during thyristor commutation. When an additional commutation voltage is applied to the full-bridge submodule, it provides conditions for current transfer; reduces the current surge and device stress during commutation; and provides more stable current turn-off conditions for the thyristor reverse recovery range.

[0046] Secondly, there is the structure of the cascaded module chain, details of which are as follows: Figure 3 As shown, each phase cascaded module chain unit consists of several sub-modules connected in series, including: A half-bridge module, denoted as HB. sm ; A full-bridge submodule, denoted as FB. sm The total number of modules per phase is . Figure 3 As shown, This represents the capacitor voltage of the j-th half-bridge submodule in the i-th phase. This represents the capacitor voltage of the j-th full-bridge submodule in phase i.

[0047] It should be noted that the number of modules is related as follows: This means that only a small number of full-bridge sub-modules are configured for each phase, while most modules still use half-bridge modules, which can ensure that the system cost will not increase significantly.

[0048] The output state of the half-bridge submodule is 0 or ,in This represents the capacitor voltage of a single submodule; the output state of the full-bridge submodule is 0. or The half-bridge submodule is mainly responsible for waveform shaping and voltage construction during normal operation. In addition to participating in waveform construction, the more important function of the full-bridge submodule is to output a negative voltage or additional commutation voltage in the commutation interval, thereby applying reverse voltage to the thyristor to be turned off.

[0049] Taking phase a as an example, the total output voltage of its half-bridge submodule is denoted as: The total output voltage of the full-bridge submodule is denoted as... Then the output voltage of the cascaded module chain of phase a is The output voltages of the cascaded module chain of phases b and c correspond to respectively .

[0050] During normal steady-state operation, the rectified sinusoidal voltage is generated by the half-bridge submodule in most cases, while the full-bridge submodule only undertakes a small amount of compensation or remains in standby mode. During commutation, the full-bridge submodule outputs a reverse voltage as the reverse blocking voltage required for the thyristor to force commutation.

[0051] In summary, thyristors are used in directional control valves to replace existing active turn-off devices (such as IGBTs and IGCTs). Using thyristors as power devices in directional control valves offers advantages such as low cost, low on-state voltage drop and losses, strong current carrying capacity, and mature high-voltage series technology. However, because thyristors are semi-controlled devices, they have the technical problem of not being able to actively turn off. To adapt to the semi-controlled characteristics of thyristors, a specific structure is adopted, using a cascaded module chain with a majority of half-bridge sub-modules connected in series with a small number of full-bridge sub-modules, and adding a commutation inductor to the half-bridge arm of the directional control valve. During commutation, the system actively outputs an additional reverse commutation voltage by controlling a small number of full-bridge sub-modules, and applies reverse voltage across the thyristor to be turned off, driving the original conducting branch current to drop to zero and maintaining the reverse voltage for a period of time, thus achieving forced commutation and reliable turn-off of the thyristor. This invention solves the thyristor commutation problem through the design of "actively applying reverse voltage by a small number of full-bridge sub-modules," thereby achieving the core innovations of lightweight equipment, low loss, and low cost.

[0052] The circuit operation principle of this invention is as follows:

[0053] Since the three phases have the same circuit structure, the working principle of the entire converter will be explained using phase a as an example. During normal operation, the output voltage of the cascaded module chain of phase a is... Its waveform is the rectified sine wave corresponding to the AC phase voltage; the output voltages of the cascaded module chain of phase b and phase c are respectively denoted as... and The output voltages of the three-phase cascaded module chain are superimposed on the DC side to form the DC bus voltage. The three-phase rectified sinusoidal voltages are 120° out of phase. When superimposed, they produce a six-pulse DC voltage. The DC bus voltage exhibits a relatively small sixth-harmonic pulsation, and its theoretical waveform is as follows: Figure 7 As shown. Low voltage fluctuations help reduce the need for submodule capacitors and DC-side filter capacitors, thereby reducing the final number of modules required, reducing size, and reducing weight.

[0054] The directional valve operates at the power frequency of 50Hz. Its main function is to reverse the polarity of the voltage, triggering the diagonal thyristor valve during the positive half-cycle of the AC voltage. , This causes the output terminal of phase a to receive a positive polarity module chain voltage; during the negative half-cycle of the AC side voltage, it triggers another pair of diagonal thyristor valves. , This causes the output terminal of phase a to receive a negative polarity module chain voltage. Through the polarity reversal of the commutation valve, the originally always positive rectified pulsating voltage... It is expanded into alternating positive and negative phase voltages on the AC side. The same principle applies to phase b and phase c, thus forming a three-phase symmetrical sinusoidal voltage and current waveform on the AC side.

[0055] Since thyristors are semi-controlled devices, when the commutation valve switches from one set of on-state valves to another, forced commutation is necessary to reliably turn off the previously on thyristors. Therefore, commutation inductors are connected in series in the left and right half-bridge arms of each phase commutation valve to limit the rate of current change during commutation and reduce device stress. Simultaneously, a small number of full-bridge sub-modules are cascaded in each phase's cascaded module chain. When the system enters the commutation phase, the full-bridge sub-modules output a reverse commutation voltage. ,in, The subscript indicates the magnitude of the reverse voltage constant 'a'. A reverse voltage is established across the thyristor to be turned off, causing the current in the original conducting branch to gradually decrease to zero. After the original conducting thyristor maintains the reverse voltage for a sufficient time, it is turned off, and the newly conducting thyristor takes over the main current, ending the commutation phase.

[0056] Under steady-state conditions, the single-phase output voltage of the three-phase cascaded module chain It can be approximated as a three-phase rectified sine wave with a phase difference of 120°; its sum is a six-pulse DC voltage. AC phase voltage and phase current It is a three-phase symmetrical sinusoidal quantity, and its theoretical waveform is as follows: Figure 1 and Figure 2 As shown. If the system operates under unity power factor conditions, the AC current is in phase with the grid phase voltage; if it operates under reactive power regulation conditions, the AC current phase will lead or lag the grid voltage by a corresponding angle.

[0057] like Figure 1 The diagram shown is a circuit topology diagram of an MCC converter. The overall architecture of the converter includes: three phase units with the same structure are cascaded on the DC side and connected to a common DC bus, and the AC side is connected to the power grid through a transformer.

[0058] like Figure 2 The diagram shown is a model of a directional valve bridge arm switch. The directional valve consists of: each valve position uses an anti-parallel thyristor to achieve bidirectional current carrying, and the commutation inductor connected in series in the bridge arm is shown to limit the rate of change of current when the thyristor is commutating.

[0059] like Figure 3 The diagram shows the structure of a cascaded module chain, specifically a full-bridge and half-bridge structure. The cascaded module chain has a module configuration ratio, with most being half-bridge sub-modules used for voltage construction and a few being full-bridge sub-modules. Their core function is to output reverse voltage in the commutation section to ensure reliable thyristor turn-off.

[0060] like Figure 4 The diagram shows the trigger signal for the a-phase thyristor to turn on: four thyristor valve units in the a-phase commutation valve ( The gate trigger timing of the converter determines the commutation time of the converter within the power frequency cycle.

[0061] like Figure 5 The diagram shown is a schematic of the grid phase voltage: a standard three-phase symmetrical sinusoidal AC voltage waveform on the converter access side.

[0062] like Figure 6 The diagram shows the AC side current (operating at unity power factor): the sinusoidal current waveform output by the AC side of the system under unity power factor conditions, which is in phase with the phase voltage.

[0063] like Figure 7 The diagram shows the DC bus voltage and the output voltage of the three-phase cascaded module chain: the rectified envelope voltage output by the three-phase cascaded module chain is superimposed on the DC side to form a DC bus voltage with low ripple characteristics.

[0064] like Figure 8 The diagram shown is a schematic of the DC bus current: the stable current waveform output by the converter on the DC side.

[0065] like Figure 9 As shown, the current flowing through the phase unit module chain of phase a is the current of the cascaded module chain, which reflects the energy throughput of the sub-module under different operating conditions.

[0066] like Figure 10 The image shows a reversing valve. , Voltage at both ends: The voltage stress borne by the thyristor valve during conduction, blocking and commutation, especially the reverse voltage applied by the full-bridge submodule at the commutation moment.

[0067] like Figure 11 The image shows a reversing valve. , The voltage across the terminals corresponds to the voltage waveform of another set of diagonal thyristor valves, and... Figure 10 The complementary nature of the directional valve reflects its polarity reversal function.

[0068] like Figure 12 As shown, the flow passes through the reversing valve. , The current: The transfer process of the main current at the commutation moment shows the forced commutation characteristics where the current is controlled to drop to zero.

[0069] like Figure 13 As shown, this is the flow through the reversing valve. , Current: The dynamic process by which the current in the newly conducting branch gradually rises to the amplitude of the main current during the commutation process.

[0070] like Figure 14 The image shows a simulated waveform of the power grid phase voltage; as shown... Figure 15 The image shows the simulated waveform of the AC input current; as shown... Figure 16 The figure shows the simulated waveforms of the DC-side voltage and the three-phase module chain voltage; as shown... Figure 17 The figure shows the simulated waveform of the three-phase module chain current. Several key electrical parameters of the converter under steady-state operation and commutation transient conditions are comprehensively presented, verifying the effectiveness of the proposed topology and control.

[0071] The specific implementation measures of this invention mainly include the following four steps:

[0072] Based on the general structure of the MCC converter, a circuit topology is constructed, and a simulation circuit model of the MCC converter is built. The three-phase structure is divided into phase a, phase b, and phase c. It includes a commutation valve, a cascaded module chain, and commutation inductors connected in series in the left and right half-bridge arms of the commutation valve. The commutation valve adopts an H-bridge structure, and the four switching valves are composed of anti-parallel thyristors. The cascaded module chain is composed of a majority of half-bridge sub-modules and a small number of full-bridge sub-modules cascaded together. The three-phase units are cascaded on the DC side and connected to a common DC bus, and on the AC side, they are connected to the AC power grid through an open-winding transformer.

[0073] Based on circuit principles, analyze the thyristor conduction timing, provide the trigger signal, and plot the theoretical waveforms of voltage and current in each part of the circuit during operation. During normal operation, the cascaded module chain outputs rectified sinusoidal voltages corresponding to the target phase voltage amplitudes on the AC side, with the three-phase output phases differing by 120°. The output voltages of the three-phase cascaded module chain are superimposed on the DC side to form the DC bus voltage. The commutator valves achieve polarity reversal under power frequency conditions, causing the originally always positive rectified pulsating voltage to unfold into alternating positive and negative phase voltages on the AC side, thus forming the three-phase AC output voltage.

[0074] Based on the turn-on and turn-off principle of thyristor semi-controlled devices, the timing sequence of the thyristor trigger signal is given. When the commutation valve needs to switch from one set of conducting valves to another, the controller first sends a trigger pulse to the valve to be turned on, and simultaneously controls a small number of full-bridge sub-modules in the cascaded module chain to output an additional reverse commutation voltage. This reverse commutation voltage is applied across the thyristor to be turned off, establishing a reverse voltage across the thyristor. At the same time, the commutation inductance connected in series in the left and right half-bridge arms of the commutation valve limits the rate of change of current during the commutation process, causing the current in the original conducting branch to gradually decrease while the current in the newly conducting branch gradually increases. When the current in the original conducting thyristor drops to zero and maintains a sufficient reverse voltage for a sufficient time, the original conducting thyristor is reliably turned off, and the newly conducting thyristor takes over the main current, completing the commutation process.

[0075] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A lightweight, high-voltage, high-capacity AC / DC converter based on thyristors and cascaded module chains, characterized in that, It includes three phase units with the same structure. The three phase units are cascaded on the DC side and connected to a common DC bus. On the AC side, they are connected to the AC power grid through an open-winding transformer. Each phase unit includes: a commutation valve and a cascade module chain, wherein the two DC terminals of the commutation valve are connected in parallel to the two sides of the cascade module chain, and the AC terminal of the commutation valve is connected to an open-winding transformer. Each of the commutation valves adopts an H-bridge topology, including two bridge arms. Each bridge arm consists of two thyristor valve units and a commutation inductor connected in series. The two bridge arms are connected in parallel, and the midpoints of the two bridge arms are respectively connected to an open-winding transformer. Each of the cascaded module chains consists of several sub-modules connected in series. The sub-modules include half-bridge sub-modules and full-bridge sub-modules, with the number of half-bridge sub-modules being greater than the number of full-bridge sub-modules.

2. The lightweight high-voltage, high-capacity AC / DC converter based on thyristors and cascaded module chains according to claim 1, characterized in that, Each of the thyristor valve units comprises a set of anti-parallel thyristors connected in series.

3. The lightweight high-voltage, high-capacity AC / DC converter based on thyristors and cascaded module chains according to claim 2, characterized in that, Each of the aforementioned directional valves includes a thyristor valve unit. and commutation inductor and ; Thyristor valve unit and and commutation inductor Comprising the first bridge arm, thyristor valve unit and and commutation inductor Forming the second bridge arm, commutation inductor One end is connected to the commutation inductor One end is connected to the commutator inductor. The other end is connected to the thyristor valve unit. One end is connected to the thyristor valve unit. The other end is connected to the thyristor valve unit. One end is connected to the thyristor valve unit. With thyristor valve unit The connection point is at the midpoint of the first bridge arm, and the commutation inductor... The other end is connected to the thyristor valve unit. One end is connected to the thyristor valve unit. The other end is connected to the thyristor valve unit. One end is connected to the thyristor valve unit. With thyristor valve unit The connection point is at the midpoint of the second bridge arm, thyristor valve unit. The other end is connected to the thyristor valve unit. The other end is connected, and the midpoints of the first and second bridge arms are respectively connected to the open-winding transformer.

4. The lightweight high-voltage, high-capacity AC / DC converter based on thyristors and cascaded module chains according to claim 1, characterized in that, Each of the cascaded module chains includes One and a half bridge submodules and There are 1 full-bridge sub-modules, and the module quantity relationship is as follows: , and All are integers greater than or equal to 1.

5. The lightweight high-voltage high-capacity AC / DC converter based on thyristors and cascaded module chains according to claim 4, characterized in that, The output state of the half-bridge submodule is 0 or ,in This represents the capacitor voltage of a single submodule; the output state of the full-bridge submodule is 0. or .

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