Converter, control method and control device thereof, and high-voltage direct-current power transmission system

Abstract

The invention discloses a current converter and a control method and device thereof, and a high-voltage direct-current transmission system, the current converter comprises a main circuit and an auxiliary circuit, the main circuit comprises a bridge arm circuit connected between an anode bus and a cathode bus, and the auxiliary circuit comprises an isolation circuit, a full-bridge circuit and a transfer circuit. According to the converter, under the condition that commutation of the bridge arm circuit of the main circuit is about to fail, the full-bridge circuit or the bridge arm circuit is controlled to provide the commutation voltage, so that the transfer circuit and the isolation circuit are conducted to transfer the current of the bridge arm circuit to the auxiliary circuit; and when the bridge arm circuit is recovered to be turned off, the full-bridge circuit is turned off to generate commutation voltage to transfer the current to another phase, so that self-commutation independent of alternating voltage is realized. The method does not need to depend on a power grid, has the self-commutation capability, can inhibit the commutation failure, and improves the reliability of high-voltage DC power transmission.

Description

[0001] This application claims priority to Chinese patent applications filed on June 30, 2025, with application number CN202510891615.6 and CN202521364352.5, respectively. Technical Field

[0002] This application relates to the field of high voltage direct current transmission technology, specifically to a converter and its control method, control device, and high voltage direct current transmission system. Background Technology

[0003] Existing high-voltage direct current (HVDC) transmission systems use grid-commutated converters. These converters offer advantages such as large capacity, low cost, low loss, fewer components, and high reliability, but they are prone to commutation failure. With the integration of intermittent renewable energy generation systems like wind power, the AC voltage support capability is decreasing, exacerbating the sensitivity of HVDC transmission to commutation failure. Therefore, there is an urgent need to improve the inherent disturbance rejection capability of HVDC transmission systems.

[0004] Existing flexible DC transmission systems use voltage source converters, which can solve the commutation failure problem and improve the DC transmission system's ability to withstand disturbances. However, they also have problems such as a large number of components, limited capacity, high cost, high loss, and low reliability.

[0005] Based on existing grid-commutated converters, a controllable turn-off grid-commutated converter can be formed by adding auxiliary circuits, or a hybrid-commutated converter can be formed by replacing the thyristors in the converter with fully controlled devices such as reverse-resistance type IGCTs (Integrated Gate Commutated Thyristors) to solve the problem of commutation failure. However, existing controllable turn-off grid-commutated converters and hybrid-commutated converters also have problems such as a large number of fully controlled devices, large capacity, high cost, increased losses, and reduced reliability. Summary of the Invention

[0006] This application provides a converter and its control method, control device, and high-voltage direct current transmission system, which can solve the commutation failure problem at low cost and improve the reliability of the high-voltage direct current transmission system.

[0007] To achieve the above objectives, according to a first aspect of this application, a converter is proposed, comprising: a main circuit, the main circuit including at least one phase bridge arm circuit, the bridge arm circuit including an upper bridge arm circuit and a lower bridge arm circuit connected in sequence, one end of the upper bridge arm circuit being connected to the anode bus, and one end of the lower bridge arm circuit being connected to the cathode bus; an auxiliary circuit, the auxiliary circuit including an upper bridge isolation circuit, a full-bridge circuit and a lower bridge isolation circuit connected in sequence, one end of the upper bridge isolation circuit being connected to the anode bus, and one end of the lower bridge isolation circuit being connected to the cathode bus; the auxiliary circuit further including at least one phase transfer circuit, the transfer circuit including an upper bridge transfer circuit and a lower bridge transfer circuit; one end of the upper bridge transfer circuit being connected between the full-bridge circuit and the lower bridge isolation circuit, and the other end of the upper bridge transfer circuit being connected to the upper bridge arm circuit or the lower bridge arm circuit; one end of the lower bridge transfer circuit being connected between the upper bridge isolation circuit and the full-bridge circuit, and the other end of the lower bridge transfer circuit being connected to the lower bridge arm circuit or the upper bridge arm circuit.

[0008] In some embodiments, the upper bridge arm circuit includes a first valve unit, the lower bridge arm circuit includes a second valve unit, one end of the first valve unit is connected to the anode bus, the other end of the first valve unit is connected to one end of the second valve unit, and the other end of the second valve unit is connected to the cathode bus.

[0009] In some embodiments, the first valve unit includes at least one single valve, and the second valve unit includes at least one single valve.

[0010] In some embodiments, the single valve of the first valve unit and / or the second valve unit is a semi-controlled valve and / or a fully controlled valve.

[0011] In some embodiments, when the first valve unit or the second valve unit comprises two single valves, the pressure ratio of the two single valves ranges from 0.1 to 10.

[0012] In some embodiments, the upper bridge transfer circuit includes a third valve unit, and the lower bridge transfer circuit includes a fourth valve unit; the single valve of the third valve unit and / or the fourth valve unit includes at least one of the following: a semi-controlled valve, and a non-controlled valve.

[0013] In some embodiments, when the first valve unit includes a single valve, the connection point between the upper bridge transfer circuit and the upper bridge arm circuit is located at the other end of the first valve unit; when the second valve unit includes a single valve, the connection point between the lower bridge transfer circuit and the lower bridge arm circuit is located at one end of the second valve unit.

[0014] In some embodiments, when the first valve unit includes two single valves, the connection point of the upper bridge transfer circuit and the upper bridge arm circuit is located between the two single valves of the first valve unit; when the second valve unit includes two single valves, the connection point of the lower bridge transfer circuit and the lower bridge arm circuit is located between the two single valves of the second valve unit.

[0015] In some embodiments, when the first valve unit comprises two single valves, the connection point between the lower bridge transfer circuit and the upper bridge arm circuit is located between the two single valves of the first valve unit; when the second valve unit comprises two single valves, the connection point between the upper bridge transfer circuit and the lower bridge arm circuit is located between the two single valves of the second valve unit.

[0016] In some embodiments, the upper bridge isolation circuit includes a fifth valve unit, and the lower bridge isolation circuit includes a sixth valve unit; the single valve of the fifth valve unit and / or the sixth valve unit includes at least one of the following: a fully controlled valve, a partially controlled valve, and a non-controlled valve.

[0017] In some embodiments, the upper bridge isolation circuit further includes a first disconnect switch or a first disconnect switch, and the lower bridge isolation circuit further includes a second disconnect switch or a second disconnect switch; the fifth valve unit is connected to the anode bus via the first disconnect switch or the first disconnect switch, and the sixth valve unit is connected to the cathode bus via the second disconnect switch or the second disconnect switch.

[0018] In some embodiments, the upper bridge isolation circuit further includes a third disconnect switch or a third disconnector, and the lower bridge isolation circuit further includes a fourth disconnect switch or a fourth disconnector; the fifth valve unit of the upper bridge isolation circuit is connected in parallel with the third disconnect switch or the third disconnector, and the sixth valve unit of the lower bridge isolation circuit is connected in parallel with the fourth disconnect switch or the fourth disconnector.

[0019] In some embodiments, the semi-controlled valve includes a one-way semi-controlled switch or a two-way semi-controlled switch; wherein, the one-way semi-controlled switch includes a plurality of semi-controlled devices connected in series; the two-way semi-controlled switch includes a plurality of first semi-controlled units connected in series, the first semi-controlled unit including a plurality of anti-parallel semi-controlled devices; or, the two-way semi-controlled switch includes a plurality of second semi-controlled units connected in anti-parallel, the second semi-controlled unit including a plurality of semi-controlled devices connected in series.

[0020] In some embodiments, the uncontrolled valve includes a plurality of uncontrolled devices connected in series.

[0021] In some embodiments, the converter further includes a first surge arrester connected in parallel with at least one of the following single valves: a single valve in a first valve unit, a single valve in a second valve unit, a single valve in a third valve unit, a single valve in a fourth valve unit, a single valve in a fifth valve unit, and a single valve in a sixth valve unit.

[0022] In some embodiments, the full-bridge circuit includes a seventh valve unit, which includes a fully controlled valve.

[0023] In some embodiments, the full-bridge circuit further includes a resistor unit or an inductor unit connected in series with the seventh valve unit.

[0024] In some embodiments, the fully controlled valve includes a one-way fully controlled switch, and / or a two-way fully controlled switch, and / or a module series switch; wherein, the one-way fully controlled switch includes a plurality of one-way fully controlled devices connected in series; the two-way fully controlled switch includes a plurality of two-way fully controlled devices or two-way fully controlled modules connected in series; and the module series switch includes a plurality of fully controlled sub-modules connected in series.

[0025] In some embodiments, the fully controlled submodule includes at least one of the following: a half-bridge submodule, a full-bridge submodule, a quasi-full-bridge submodule, a midpoint clamping submodule, a dual half-bridge series submodule, a dual full-bridge series submodule, a clamping dual submodule, a cross-connected dual submodule, a self-resisting submodule, or a diode clamping submodule.

[0026] In some embodiments, the fully controlled submodule includes a capacitor and / or a battery.

[0027] In some embodiments, the full-bridge circuit further includes a second surge arrester, which is connected in parallel with the full control valve, a plurality of the unidirectional full control devices, a plurality of the bidirectional full control devices, a plurality of the bidirectional full control modules, or a plurality of the full control sub-modules.

[0028] In some embodiments, the common terminal of the upper bridge arm circuit and the lower bridge arm circuit serves as a phase output terminal and is connected to the AC system via a transformer or reactor.

[0029] In some embodiments, the converter further includes a voltage source converter. When the main circuit includes a three-phase bridge arm circuit, the voltage source converter adopts a three-phase star connection or delta connection circuit, and is connected in parallel with the three phases of the main circuit at the phase output terminal.

[0030] In some embodiments, the converter further includes an energy storage circuit, one end of which is connected to the anode bus and the other end of which is connected to the cathode bus; the energy storage circuit includes a module series switch.

[0031] In a second aspect of this application, a control method for a converter is proposed for controlling the converter described in the first aspect. The method includes: generating a switching control command when the operating state of the converter meets a transfer condition; turning on a target auxiliary circuit corresponding to the bridge arm to be turned off in the converter according to the switching control command, so as to switch the current of the bridge arm to be turned off to the target auxiliary circuit; generating a turn-off command when the bridge arm to be turned off resumes its turn-off state, and controlling the target auxiliary circuit to output a commutation voltage to the bridge arm to be turned on according to the turn-off command, so as to realize a commutation operation from the bridge arm to be turned off to the bridge arm to be turned on.

[0032] In some embodiments, the target auxiliary circuit includes a target transfer circuit, a target isolation circuit, and a full-bridge circuit corresponding to the bridge arm to be turned off; the step of turning on the target auxiliary circuit corresponding to the bridge arm to be turned off in the converter according to the switching control command includes: turning on the target transfer circuit and the target isolation circuit according to the switching control command, and controlling the full-bridge circuit to generate a commutation voltage so that the current of the bridge arm to be turned off is switched to the target auxiliary circuit.

[0033] In some embodiments, the target auxiliary circuit includes a target transfer circuit, a target isolation circuit, and a full-bridge circuit corresponding to the bridge arm to be turned off; the step of turning on the target auxiliary circuit corresponding to the bridge arm to be turned off in the converter according to the switching control command includes: turning on the target transfer circuit, the target isolation circuit, and the full-bridge circuit according to the switching control command, turning off the full control valve of the bridge arm to be turned off, and controlling the full control valve to generate a commutation voltage so that the current of the bridge arm to be turned off is switched to the target auxiliary circuit.

[0034] In some embodiments, generating a shutdown command when the bridge arm to be shut down recovers to shut down includes generating the shutdown command when the reverse recovery time of a single valve in the bridge arm to be shut down is greater than or equal to the reverse recovery time of the thyristor in the single valve.

[0035] In some embodiments, the method further includes: during the non-commutation period of the converter, controlling the conduction of the isolation circuit and / or the transfer circuit corresponding to the non-conducting bridge arm of the converter to charge or discharge the fully controlled submodule of a single valve in the full-bridge circuit of the converter.

[0036] In some embodiments, the method further includes: charging and discharging different full-bridge sub-modules in the full-bridge circuit via DC-side control to maintain voltage balance in the full-bridge circuit.

[0037] In some embodiments, when the converter is operating normally, the method further includes: generating the shutdown command in advance when the capacitor voltage of the full-bridge circuit of the converter is less than a first preset value; and delaying the generation of the shutdown command when the capacitor voltage of the full-bridge circuit of the converter is greater than a second preset value.

[0038] In some embodiments, the switching conditions include at least one of the following: the converter commutates when the shut-off angle reference value is less than the minimum shut-off angle in inverter mode; the converter commutates when the firing angle reference value is less than the minimum firing angle in rectifier mode; the converter commutates when a commutation fault exists in inverter mode.

[0039] In some embodiments, the converter employs a grid control strategy.

[0040] In some embodiments, where the converter further includes an energy storage circuit, the method further includes: controlling the charging and discharging of the energy storage circuit to enable the converter to interact with the AC system.

[0041] In some embodiments, the method further includes: in the event of a fault in the auxiliary circuit of the converter, disconnecting the first disconnecting switch or the first disconnector between the fifth valve unit of the upper bridge isolation circuit in the converter and the bus, and the second disconnecting switch or the second disconnector between the sixth valve unit of the lower bridge isolation circuit in the converter and the bus.

[0042] In a third aspect of this application, a control device for a converter is provided for controlling the converter described in the first aspect above. The device includes: an instruction generation module for generating a switching control instruction when the converter meets the switching conditions; a switching module for turning on a target auxiliary circuit corresponding to the bridge arm to be turned off in the converter according to the switching control instruction, so as to switch the current of the bridge arm to be turned off to the target auxiliary circuit; and a commutation module for generating a turn-off instruction when the bridge arm to be turned off resumes its turn-off state, and controlling the target auxiliary circuit to output a commutation voltage to the bridge arm to be turned on according to the turn-off instruction, so as to realize the commutation operation from the bridge arm to be turned off to the bridge arm to be turned on.

[0043] In a fourth aspect of this application, a high-voltage direct current (HVDC) transmission system is provided, wherein at least one converter in the HVDC transmission system is a converter as described in the first aspect above.

[0044] In some embodiments, the high-voltage direct current transmission system includes a two-terminal direct current transmission system or a multi-terminal direct current transmission system.

[0045] In some embodiments, the high-voltage direct current transmission system includes a monopolar direct current transmission system, a bipolar direct current transmission system, or a back-to-back direct current transmission system.

[0046] In summary, the converter proposed in this application includes a main circuit and an auxiliary circuit. The main circuit includes at least one phase bridge arm circuit. The bridge arm circuit includes an upper bridge arm circuit and a lower bridge arm circuit connected in sequence. One end of the upper bridge arm circuit is connected to the anode bus, and one end of the lower bridge arm circuit is connected to the cathode bus. The auxiliary circuit includes an upper bridge isolation circuit, a full-bridge circuit, and a lower bridge isolation circuit connected in sequence. One end of the upper bridge isolation circuit is connected to the anode bus, and one end of the lower bridge isolation circuit is connected to the cathode bus. The auxiliary circuit also includes at least one phase transfer circuit, which includes an upper bridge transfer circuit and a lower bridge transfer circuit. One end of the upper bridge transfer circuit is connected between the full-bridge circuit and the lower bridge isolation circuit, and the other end of the upper bridge transfer circuit is connected to either the upper bridge arm circuit or the lower bridge arm circuit. One end of the lower bridge transfer circuit is connected between the upper bridge isolation circuit and the full-bridge circuit, and the other end of the lower bridge transfer circuit is connected to either the lower bridge arm circuit or the upper bridge arm circuit.

[0047] The converter provided in this application embodiment, in the event of commutation failure in the main circuit's bridge arm circuit, provides commutation voltage by controlling the full-bridge circuit or bridge arm circuit in the auxiliary circuit. This causes the transfer circuit and isolation circuit to conduct, forming a parallel current with the bridge arm circuit of the main circuit, transferring current from the bridge arm circuit to the auxiliary circuit. When the bridge arm circuit resumes its off state, the commutation voltage is generated by turning off the full-bridge circuit, thus achieving the shutdown of the bridge arm circuit before the commutation operation. This application embodiment does not rely on the power grid, effectively solving the commutation failure problem, enabling the converter to achieve controllable shutdown. Furthermore, when the full-bridge circuit uses modular series switches, it can be continuously shut down, reducing the reference values ​​of the shutdown angle or trigger angle, thereby reducing reactive power consumption. Since the auxiliary circuit of the converter in this application embodiment is configured with only one full-bridge circuit, the converter shares only one full-bridge circuit, and the converter station only needs to be configured with fewer reactive power compensation devices, thereby reducing the cost of the high-voltage direct current transmission system with controllable shutdown capability and improving its reliability. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the topology of a self-commutated converter provided in an embodiment of this application; Figure 2 This is a schematic diagram of another self-commutated converter topology provided in an embodiment of this application; Figure 3 This is a schematic diagram of another self-commutated converter topology provided in an embodiment of this application; Figure 4 This is a schematic diagram of another self-commutated converter topology provided in an embodiment of this application; Figure 5 This is a topology diagram of a controllable shutdown hybrid grid phase-commutation converter provided in an embodiment of this application; Figure 6This is a schematic diagram of another controllable shutdown hybrid grid phase-commutation converter provided in the embodiments of this application; Figure 7 This is a schematic diagram of another controllable shutdown hybrid grid phase-commutation converter provided in the embodiments of this application; Figure 8 This is a schematic diagram of another controllable shutdown hybrid grid phase-commutation converter provided in the embodiments of this application; Figure 9 This is a schematic diagram of the valve unit provided in the embodiment of this application; Figure 10A This is a schematic diagram of the full-bridge submodule provided in an embodiment of this application; Figure 10B This is a schematic diagram of a full-bridge submodule provided in an embodiment of this application; Figure 11 This is a circuit diagram of a self-commutated converter provided in an embodiment of this application; Figure 12 This is a circuit diagram of another self-commutated converter provided in an embodiment of this application; Figure 13 This is a circuit diagram of another self-commutated converter provided in an embodiment of this application; Figure 14 This is a circuit diagram of another self-commutated converter provided in an embodiment of this application; Figure 15 This is a circuit diagram of another self-commutated converter provided in an embodiment of this application; Figure 16 This is a circuit diagram of another self-commutated converter provided in an embodiment of this application; Figure 17 This is a circuit diagram of a controllable shutdown hybrid grid phase-commutation converter provided in an embodiment of this application; Figure 18 This is a circuit diagram of another controllable shutdown hybrid grid phase-commutation converter provided in the embodiments of this application; Figure 19 This is a circuit diagram of another controllable shutdown hybrid grid phase-commutation converter provided in the embodiments of this application; Figure 20 This is a circuit diagram of another controllable shutdown hybrid grid phase-commutation converter provided in the embodiments of this application; Figure 21 This is a circuit diagram of another controllable shutdown hybrid grid phase-commutation converter provided in the embodiments of this application; Figure 22 This is a circuit diagram of another controllable shutdown hybrid grid phase-commutation converter provided in the embodiments of this application; Figure 23 This is a flowchart of a converter control method provided in an embodiment of this application; Figure 24 This is a schematic diagram of a converter control module provided in an embodiment of this application; Figure 25 This is a schematic diagram of the structure of a single pole of a high-voltage direct current transmission system provided in an embodiment of this application; Figure 26 This is a schematic diagram of the structure of another single pole of a high-voltage direct current transmission system provided in an embodiment of this application; Figure 27A This is a test waveform of the converter provided in this application embodiment during a phase A ground fault in an AC system; Figure 27B These are the test waveforms of the converter provided in this application during short-circuit faults in phases A and B of the AC system; Figure 27C This is a test waveform of the converter provided in this application during a three-phase short-circuit fault in an AC system. Detailed Implementation

[0049] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0050] Furthermore, in the embodiments of this application, "multiple" refers to two or more. In the embodiments of this application, "first" and "second," etc., are used to distinguish different technical features and do not indicate any order, quantity, or importance. In the embodiments of this application, "comprising" and "including" indicate the presence of the described feature, whole, step, operation, element, and / or component, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or sets thereof.

[0051] The various embodiments provided in this application are similar, and features in different embodiments can be combined with each other.

[0052] The order in which the following embodiments are described is not intended to limit the preferred order of the embodiments.

[0053] With the increasing number of high-voltage and ultra-high-voltage direct current (HVDC) transmission systems being connected, multi-infeed HVDC transmission systems are forming in multiple regional power grids. In such systems, simultaneous commutation failures on multiple HVDC transmission lines can seriously jeopardize the safe operation of the power grid in the affected region. Furthermore, the increasing proportion of renewable energy generation and the decreasing AC voltage support capacity place higher demands on the stability of HVDC transmission system operations and its ability to suppress commutation failures.

[0054] To address the problems of commutation failure, reliance on AC voltage support, and high reactive power consumption during faults in current power grid commutation converters, this application provides a converter that can suppress commutation failure at low cost, commutate without relying on AC voltage, reduce reactive power consumption during faults, and improve the reliability of DC transmission systems.

[0055] In a first aspect, this application provides a converter, comprising: a main circuit, the main circuit including at least one phase bridge arm circuit, the bridge arm circuit including an upper bridge arm circuit and a lower bridge arm circuit connected in sequence, one end of the upper bridge arm circuit being connected to the anode bus, and one end of the lower bridge arm circuit being connected to the cathode bus; an auxiliary circuit, the auxiliary circuit including an upper bridge isolation circuit, a full-bridge circuit and a lower bridge isolation circuit connected in sequence, one end of the upper bridge isolation circuit being connected to the anode bus, and one end of the lower bridge isolation circuit being connected to the cathode bus; the auxiliary circuit further including at least one phase transfer circuit, the transfer circuit including an upper bridge transfer circuit and a lower bridge transfer circuit; one end of the upper bridge transfer circuit being connected between the full-bridge circuit and the lower bridge isolation circuit, and the other end of the upper bridge transfer circuit being connected to the upper bridge arm circuit or the lower bridge arm circuit; one end of the lower bridge transfer circuit being connected between the upper bridge isolation circuit and the full-bridge circuit, and the other end of the lower bridge transfer circuit being connected to the lower bridge arm circuit or the upper bridge arm circuit.

[0056] like Figure 1 The schematic diagram of the topology of the self-commutated converter shown in this application embodiment includes a main circuit and an auxiliary circuit. The main circuit includes at least one phase bridge arm circuit. The bridge arm circuit includes an upper bridge arm circuit 1 and a lower bridge arm circuit 2 connected in sequence. One end of the upper bridge arm circuit 1 is connected to the anode bus, and one end of the lower bridge arm circuit 2 is connected to the cathode bus. The auxiliary circuit includes an upper bridge isolation circuit 5, a full-bridge circuit 7, and a lower bridge isolation circuit 6 connected in sequence. One end of the upper bridge isolation circuit 5 is connected to the anode bus, and one end of the lower bridge isolation circuit 6 is connected to the cathode bus. The auxiliary circuit also includes at least one phase transfer circuit. The transfer circuit includes an upper bridge transfer circuit 3 and a lower bridge transfer circuit 4. One end of the upper bridge transfer circuit 3 is connected between the full-bridge circuit 7 and the lower bridge isolation circuit 6, and the other end of the upper bridge transfer circuit 3 is connected to either the upper bridge arm circuit 1 or the lower bridge arm circuit 2. One end of the lower bridge transfer circuit 4 is connected between the upper bridge isolation circuit 5 and the full-bridge circuit 7, and the other end of the lower bridge transfer circuit 4 is connected to either the lower bridge arm circuit 2 or the upper bridge arm circuit 1.

[0057] Please see Figure 1 The diagram shows the structure of a self-commutated current transformer. Figure 1As shown, the main circuit includes a three-phase bridge arm circuit, with each phase corresponding to one phase of the AC power supply, and all bridge arm circuits are connected in parallel. Each phase bridge arm circuit includes an upper bridge arm circuit 1 and a lower bridge arm circuit 2 connected in sequence. The three-phase bridge arm circuit includes three bridge arm circuits connected in parallel, and each bridge arm circuit includes an upper bridge arm circuit 1 and a lower bridge arm circuit 2. One end of the upper bridge arm circuit 1 is connected to the anode bus P1, and one end of the lower bridge arm circuit 2 is connected to the cathode bus N1.

[0058] Please continue reading. Figure 1 The auxiliary circuit includes an upper bridge isolation circuit 5, a full bridge circuit 7, and a lower bridge isolation circuit 6 connected in sequence. One end of the upper bridge isolation circuit 5 is connected to the anode bus P1, and one end of the lower bridge isolation circuit 6 is connected to the cathode bus N1.

[0059] The auxiliary circuit also includes at least one phase transfer circuit, which is connected to the bridge arm circuit. It is understood that the transfer circuit in this embodiment corresponds to the bridge arm circuit. When the main circuit includes a three-phase bridge arm circuit, the auxiliary circuit includes three-phase transfer circuits connected to the bridge arm circuit, with each phase transfer circuit corresponding to one phase of the AC power.

[0060] The transfer circuit includes an upper bridge transfer circuit 3 and a lower bridge transfer circuit 4. For ease of description later, in this embodiment, the connection line between the full-bridge circuit 7 and the upper bridge isolation circuit 5 is defined as the transfer cathode connection line N2, and the connection line between the full-bridge circuit 7 and the lower bridge isolation circuit 6 is defined as the transfer anode connection line P2. One end of the upper bridge transfer circuit 3 is connected to the transfer anode connection line P2, and the other end is connected to the upper bridge arm circuit 1 or the lower bridge arm circuit 2. One end of the lower bridge transfer circuit 4 is connected to the transfer cathode connection line N2, and the other end is connected to the lower bridge arm circuit 2 or the upper bridge arm circuit 1. One end of the full-bridge circuit 7 is connected to the transfer anode connection line P2, and the other end is connected to the transfer cathode connection line N2.

[0061] When the upper bridge transfer circuit 3 is connected to the bridge arm circuit, it can be connected to either the upper bridge arm circuit 1 or the lower bridge arm circuit 2. Similarly, when the lower bridge transfer circuit 4 is connected to the bridge arm circuit, it can be connected to either the lower bridge arm circuit 2 or the upper bridge arm circuit 1. It should be noted that when the upper bridge transfer circuit 3 is connected to the upper bridge arm circuit 1, the lower bridge transfer circuit 4 is connected to the lower bridge arm circuit 2. Conversely, when the upper bridge transfer circuit 3 is connected to the lower bridge arm circuit 2, the lower bridge transfer circuit 4 is connected to the upper bridge arm circuit 1.

[0062] Please continue reading. Figure 1 One end of the upper bridge transfer circuit 3 is connected to the transfer anode connection line P2, and the other end is connected to the upper bridge arm circuit 1; one end of the lower bridge transfer circuit 4 is connected to the transfer cathode connection line N2, and the other end is connected to the lower bridge arm circuit 2.

[0063] The self-commutated converter proposed in this application, when the bridge arm circuit of the main circuit is about to fail to commutate, provides a commutation voltage by controlling the full-bridge circuit in the auxiliary circuit, so that the transfer circuit and the isolation circuit are turned on to form a parallel current with the bridge arm circuit, and transfer the current from the bridge arm circuit to the auxiliary circuit; when the bridge arm circuit is turned off again, the commutation voltage generated by turning off the full-bridge circuit is used to transfer the current to another phase, thus realizing self-commutation operation that does not depend on AC voltage.

[0064] The embodiments of this application can effectively solve the commutation failure problem, enabling the self-commutated converter to achieve controllable shutdown. Furthermore, the full-bridge circuit can be continuously shut off in steady state, reducing the reference values ​​for the shutdown angle or firing angle, thereby reducing reactive power consumption. Since the auxiliary circuit of the self-commutated converter in this application embodiment only requires one full-bridge circuit, and the converter station only needs to be equipped with fewer reactive power compensation devices, the cost of the high-voltage direct current transmission system with controllable shutdown capability is reduced, and its reliability is improved.

[0065] In some embodiments, the upper bridge arm circuit 1 includes a first valve unit, and the lower bridge arm circuit 2 includes a second valve unit. One end of the first valve unit is connected to the anode bus P1, and the other end of the first valve unit is connected to one end of the second valve unit. The other end of the second valve unit is connected to the cathode bus N1.

[0066] The first valve unit controls the on / off state of the upper bridge arm circuit 1, and the second valve unit controls the on / off state of the lower bridge arm circuit 2. The bridge arm circuits achieve the conversion between alternating current and direct current through the orderly on / off state of the first and / or second valve units.

[0067] In some embodiments, the first valve unit includes at least one single valve, and the second valve unit includes at least one single valve.

[0068] A single valve is a series-connected group of devices that are controlled to turn on and off. For example, a single valve consists of dozens to hundreds of thyristor stages connected in series, and integrates a complete electromechanical module with auxiliary equipment such as damping circuits, voltage-equalizing resistors, reactors, surge arresters, cooling interfaces, and monitoring interfaces. A single valve is used to form a single bridge arm circuit, and six bridge arm circuits are used to form a converter valve. The converter valve can operate in rectification mode to convert AC to DC, or in inverter mode to convert DC to AC.

[0069] Figure 1 In the bridge arm circuit shown, both the first valve unit and the second valve unit include a single valve. Please continue reading. Figure 1 In the three-phase bridge arm circuit, the single valve of the upper bridge arm circuit 1 of phase A is... Figure 1The valve in phase A is labeled V41, and the single valve in phase B lower arm circuit 2 is labeled V11. One end of valve V41 is connected to the anode bus P1, and the other end is connected to phase A lower arm circuit 2. One end of valve V11 is connected to the cathode bus N1, and the other end is connected to phase A upper arm circuit 1. The single valve in phase B upper arm circuit 1 is labeled V61, and the single valve in phase B lower arm circuit 2 is labeled V31. One end of valve V61 is connected to the anode bus P1, and the other end is connected to phase B lower arm circuit 2. One end of valve V31 is connected to the cathode bus N1, and the other end is connected to phase B upper arm circuit 1. The single valve in phase C upper arm circuit 1 is labeled V21, and the single valve in phase C lower arm circuit 2 is labeled V51. One end of valve V21 is connected to the anode bus P1, and the other end is connected to phase C lower arm circuit 2. One end of valve V51 is connected to the cathode bus N1, and the other end is connected to phase C upper arm circuit 1.

[0070] Figure 2 In the bridge arm circuit shown, both the first and second valve units consist of two single valves connected in series. Please refer to... Figure 2 The three-phase bridge arm current is regulated. The first valve unit of the upper bridge arm circuit 1 of phase A includes single valves V41 and V42 connected in series, and the second valve unit of the lower bridge arm circuit 2 includes single valves V11 and V12 connected in series. One end of single valve V41 is connected to the anode bus P1, and the other end is connected to one end of single valve V42. The other end of single valve V42 is connected to the lower bridge arm circuit 2 of phase A. One end of single valve V11 is connected to the cathode bus N1, and the other end is connected to one end of single valve V12. The other end of single valve V12 is connected to the upper bridge arm circuit 1 of phase A.

[0071] The first valve unit of the upper bridge arm circuit 1 of phase B includes single valves V61 and V62 connected in series, and the second valve unit of the lower bridge arm circuit 2 includes single valves V31 and V32 connected in series. One end of single valve V61 is connected to the anode bus P1, and the other end is connected to one end of single valve V62. The other end of single valve V62 is connected to the lower bridge arm circuit 2 of phase B. One end of single valve V31 is connected to the cathode bus N1, and the other end is connected to one end of single valve V32. The other end of single valve V32 is connected to the upper bridge arm circuit 1 of phase B.

[0072] The first valve unit of the upper bridge arm circuit 1 of phase C includes single valves V21 and V22 connected in series, and the second valve unit of the lower bridge arm circuit 2 includes single valves V51 and V52 connected in series. One end of single valve V21 is connected to the anode bus P1, and the other end is connected to one end of single valve V22. The other end of single valve V22 is connected to the lower bridge arm circuit 2 of phase C. One end of single valve V51 is connected to the cathode bus N1, and the other end is connected to one end of single valve V52. The other end of single valve V52 is connected to the upper bridge arm circuit 1 of phase C.

[0073] In some embodiments, the single valve of the first valve unit and / or the second valve unit is a semi-controlled valve and / or a fully controlled valve.

[0074] For example, a semi-controlled valve refers to a semiconductor device that achieves partial control functionality through an external control signal. For instance, a semi-controlled valve can be turned on by an external control signal, but its shutdown depends on the characteristics of the device itself. A fully controlled valve refers to a device that can be turned on and off by an external control signal.

[0075] In some embodiments, the first valve unit and / or the second valve unit further include an inductor connected in series with the semi-controlled valve.

[0076] In some embodiments, the semi-controlled valve further includes an inductor connected in series with a thyristor.

[0077] In some embodiments, when the first valve unit or the second valve unit comprises two single valves, the pressure ratio of the two single valves ranges from 0.1 to 10.

[0078] The withstand voltage ratio of a single valve indicates the maximum voltage that the single valve can withstand. In practical applications, the withstand voltage of a single valve must meet the system's rated voltage and overvoltage requirements to ensure reliable operation under various conditions. When both the first and second valve units consist of two single valves, the withstand voltage ratio between the two valves indicates the voltage distribution among them; generally, the valve with the higher withstand voltage can withstand higher voltages.

[0079] Please continue reading. Figure 2 Taking the A-phase bridge arm circuit as an example, the A-phase upper bridge arm circuit 1 includes single valves V21 and V22 connected in series. The withstand voltage ratio of single valves V21 and V22 ranges from 0.2 to 5, meaning the ratio of the withstand voltage ratio of single valve V21 to that of single valve V22 is within the range of 0.2 to 5. It can be understood that when the valve unit in the A-phase lower bridge arm circuit 2, the B-phase or C-phase upper bridge arm circuit, or the B-phase or C-phase lower bridge arm circuit includes two single valves, the withstand voltage ratio range of the single valve in the valve unit is similar to that in the A-phase upper bridge arm circuit described above, and will not be repeated here.

[0080] In some embodiments, the upper bridge transfer circuit 3 includes a third valve unit, and the lower bridge transfer circuit 4 includes a fourth valve unit; the single valve of the third valve unit or the fourth valve unit includes a semi-controlled valve or an uncontrolled valve.

[0081] The third valve unit controls the on / off state of the upper bridge transfer circuit 3, and the fourth valve unit controls the on / off state of the lower bridge transfer circuit 4. The transfer circuits can achieve current flow through the upper bridge transfer circuit 3 and the lower bridge transfer circuit 4 in the event of a commutation failure in the bridge arm circuit via the orderly on / off state of the third and / or fourth valve units. Each valve in the third or fourth valve unit can be a semi-controlled valve or an uncontrolled valve.

[0082] For example, a semi-controlled valve refers to a semiconductor device that achieves partial control functionality through an external control signal. For instance, a semi-controlled valve can be turned on by an external control signal, but its turning off depends on the characteristics of the device itself. An uncontrolled valve refers to a device whose on or off state cannot be determined by an external control signal, such as an uncontrolled switch or diode.

[0083] The following examples illustrate the specific connection methods of the transfer circuit.

[0084] In some embodiments, when the first valve unit includes a single valve, the connection point between the upper bridge transfer circuit 3 and the upper bridge arm circuit 1 is located at the other end of the first valve unit; when the second valve unit includes a single valve, the connection point between the lower bridge transfer circuit 4 and the lower bridge arm circuit 2 is located at the other end of the second valve unit. The other end of the first valve unit is the connection point between the first valve unit and the second valve unit. The other end of the second valve unit is the connection point between the second valve unit and the first valve unit.

[0085] In some embodiments, the upper bridge transfer circuit 3 is connected to the upper bridge arm circuit 1, and the lower bridge transfer circuit 4 is connected to the lower bridge arm circuit 2. For example... Figure 1 As shown, taking the A-phase transfer circuit as an example, the single valve of the third valve unit in the upper bridge transfer circuit 3 is labeled V43, and the single valve of the fourth valve unit in the lower bridge transfer circuit 4 is labeled V13. One end of the single valve V43 in the third valve unit is connected to the transfer anode connection line P2, and the other end is connected to the single valve V41 in the upper bridge arm circuit 1. One end of the single valve V13 in the fourth valve unit is connected to the transfer cathode connection line N2, and the other end is connected to the single valve V11 in the lower bridge arm circuit 2. Figure 1 As shown, when single valve V43 is connected to single valve V41, it is connected between single valve V41 and single valve V11; similarly, when single valve V13 is connected to single valve V11, it is also connected between single valve V41 and single valve V11. It should be noted that when both the first and second valve units include inductors, single valve V43 and single valve V41 can share an inductor, and single valve V13 and single valve V11 can also share an inductor. It can be understood that the connection methods of the B-phase transfer circuit and the C-phase transfer circuit are similar to those of the A-phase transfer circuit, and will not be elaborated upon here.

[0086] In some embodiments, the upper bridge transfer circuit 3 is connected to the lower bridge arm circuit 2, and the lower bridge transfer circuit 4 is connected to the upper bridge arm circuit 1. For example... Figure 3 As shown, taking the A-phase transfer circuit as an example, one end of the single valve V43 of the third valve unit is connected to the transfer anode connection line P2, and the other end is connected to the single valve V11 of the lower bridge arm circuit 2. One end of the single valve V13 of the fourth valve unit is connected to the transfer cathode connection line N2, and the other end is connected to the single valve V41 of the upper bridge arm circuit 1. Figure 3As shown, when single valve V43 is connected to single valve V11, it is connected between single valve V11 and single valve V41; similarly, when single valve V13 is connected to single valve V41, it is also connected between single valve V41 and single valve V11. It should be noted that when both the first and second valve units include inductors, single valve V43 and single valve V11 can share an inductor, and single valve V13 and single valve V41 can also share an inductor. It can be understood that the connection methods of the B-phase transfer circuit and the C-phase transfer circuit are similar to those of the A-phase transfer circuit, and will not be elaborated upon here.

[0087] In some embodiments, when the first valve unit comprises two single valves, the connection point between the upper bridge transfer circuit 3 and the upper bridge arm circuit 1 is located between the two single valves of the first valve unit. When the second valve unit comprises two single valves, the connection point between the lower bridge transfer circuit 4 and the lower bridge arm circuit 2 is located between the two single valves of the second valve unit.

[0088] Please continue reading. Figure 2 Taking the connection of the A-phase bridge arm circuit and the A-phase transfer circuit as an example, the first valve unit of the upper bridge arm circuit 1 of phase A includes two single valves, V41 and V42 connected in series; the second valve unit of the lower bridge arm circuit 2 of phase A includes two single valves, V11 and V12 connected in series. When the upper bridge transfer circuit 3 is connected to the upper bridge arm circuit 1, one end of the single valve V43 of the upper bridge transfer circuit 3 is connected to the transfer anode connection line P2, and the other end is connected between single valves V41 and V42. When the lower bridge transfer circuit 4 is connected to the lower bridge arm circuit 2, one end of the single valve V13 of the lower bridge transfer circuit 4 is connected to the transfer cathode connection line N2, and the other end is connected between single valves V11 and V12. The connection methods of the B-phase bridge arm circuit and the B-phase transfer circuit, as well as the C-phase bridge arm circuit and the C-phase transfer circuit, are similar to those of phase A, and will not be described again here.

[0089] In some embodiments, when the first valve unit comprises two single valves, the connection point between the lower bridge transfer circuit 4 and the upper bridge arm circuit 1 is located between the two single valves of the first valve unit. When the second valve unit comprises two single valves, the connection point between the upper bridge transfer circuit 3 and the lower bridge arm circuit 2 is located between the two single valves of the second valve unit.

[0090] like Figure 4The self-commutated converter shown takes the connection of the A-phase bridge arm circuit and the A-phase transfer circuit as an example. The first valve unit of the upper bridge arm circuit 1 of phase A includes two single valves, V41 and V42 connected in series; the second valve unit of the lower bridge arm circuit 2 of phase A includes two single valves, V11 and V12 connected in series. When the upper bridge transfer circuit 3 of phase A is connected to the lower bridge arm circuit 2 of phase A, one end of the single valve V43 of the upper bridge transfer circuit 3 is connected to the transfer anode connection line P2, and the other end is connected between the single valves V11 and V12. When the lower bridge transfer circuit 4 is connected to the upper bridge arm circuit 1, one end of the single valve V13 of the lower bridge transfer circuit 4 is connected to the transfer cathode connection line N2, and the other end is connected between the single valves V41 and V42. The connection methods of the B-phase bridge arm circuit and the B-phase transfer circuit, as well as the C-phase bridge arm circuit and the C-phase transfer circuit, are similar to those of phase A, and will not be described again here.

[0091] In some embodiments, please refer to Figure 5 , Figure 5 This is a topology diagram of a controllable shutdown hybrid grid phase-commutation converter provided in an embodiment of this application. Figure 5 As shown, the controllable shutdown hybrid grid phase-commutation converter includes a main circuit and an auxiliary circuit. The main circuit includes at least one phase bridge arm circuit. Each phase bridge arm circuit includes an upper bridge arm circuit 1 and a lower bridge arm circuit 2 connected in series between the anode bus P1 and the cathode bus N1. The upper bridge arm circuit 1 includes a first fully controlled valve, a first partially controlled valve, and a second partially controlled valve connected in series. The lower bridge arm circuit 2 includes a second fully controlled valve, a third partially controlled valve, and a fourth partially controlled valve connected in series. The auxiliary circuit includes an upper bridge isolation circuit 5, a full bridge circuit 7, and a lower bridge isolation circuit 6 connected in series between the anode bus P1 and the cathode bus N1. The auxiliary circuit also includes a transfer circuit corresponding to each phase bridge arm circuit. The transfer circuit includes an upper bridge transfer circuit 3 and a lower bridge transfer circuit 4. One end of the upper bridge transfer circuit 3 is connected between the full bridge circuit 7 and the lower bridge isolation circuit 6, and the other end is connected to the upper bridge arm circuit 1 of the corresponding phase. One end of the lower bridge transfer circuit 4 is connected between the full bridge circuit 7 and the upper bridge isolation circuit 5, and the other end is connected to the lower bridge arm circuit 2 of the corresponding phase.

[0092] The upper bridge transfer circuit 3 is connected between the first fully controlled valve and the first partially controlled valve, and the lower bridge transfer circuit 4 is connected between the second fully controlled valve and the third partially controlled valve; or, the upper bridge transfer circuit 3 is connected between the first partially controlled valve and the second partially controlled valve, and the lower bridge transfer circuit 4 is connected between the third partially controlled valve and the fourth partially controlled valve; or, the upper bridge transfer circuit 3 is connected between the third partially controlled valve and the fourth partially controlled valve, and the lower bridge transfer circuit 4 is connected between the first partially controlled valve and the second partially controlled valve; or, the upper bridge transfer circuit 3 is connected between the second fully controlled valve and the third partially controlled valve, and the lower bridge transfer circuit 4 is connected between the first fully controlled valve and the first partially controlled valve.

[0093] Please continue reading. Figure 5The main circuit includes a three-phase bridge arm circuit, with each phase corresponding to one phase of the AC power supply, and all bridge arm circuits connected in parallel. Each phase bridge arm circuit includes an upper bridge arm circuit 1 and a lower bridge arm circuit 2 connected in sequence. Each bridge arm circuit includes a component connected in series between the anode bus P1 and the cathode bus N1, that is, the first end of the upper bridge arm circuit 1 is connected to the anode bus P1, the second end of the upper bridge arm circuit 1 is connected to the first end of the lower bridge arm circuit 2, and the second end of the lower bridge arm circuit 2 is connected to the cathode bus N1.

[0094] Phase A upper arm circuit 1 includes a first fully controlled valve V44, a first partially controlled valve V45, and a second partially controlled valve V46 connected in series. Phase A lower arm circuit 2 includes a second fully controlled valve V14, a third partially controlled valve V15, and a fourth partially controlled valve V16 connected in series.

[0095] Phase B upper arm circuit 1 includes a first fully controlled valve V64, a first partially controlled valve V65, and a second partially controlled valve V66 connected in series. Phase B lower arm circuit 2 includes a second fully controlled valve V34, a third partially controlled valve V35, and a fourth partially controlled valve V36 connected in series.

[0096] The upper arm circuit 1 of phase C includes a first fully controlled valve V24, a first partially controlled valve V25, and a second partially controlled valve V26 connected in series. The lower arm circuit 2 of phase C includes a second fully controlled valve V54, a third partially controlled valve V55, and a fourth partially controlled valve V56 connected in series.

[0097] It should be noted that the positions of the fully controlled valves and partially controlled valves in the bridge arm circuits can be interchanged. Taking the A-phase bridge arm circuit as an example, the upper bridge arm circuit 1 of phase A can also include the first partially controlled valve V45, the second partially controlled valve V46, and the first fully controlled valve V44 connected in series. The lower bridge arm circuit 2 of phase A correspondingly includes the third partially controlled valve V15, the fourth partially controlled valve V16, and the second fully controlled valve V14 connected in series. The upper bridge arm circuit 1 of phase A can also include the first partially controlled valve V45, the first fully controlled valve V44, and the second partially controlled valve V46 connected in series. The lower bridge arm circuit 2 of phase A correspondingly includes the third partially controlled valve V15, the second fully controlled valve V14, and the fourth partially controlled valve V16 connected in series. The same applies to phases B and C, and will not be elaborated here.

[0098] In this embodiment, the upper bridge transfer circuit 3 can be connected to either the upper bridge arm circuit 1 or the lower bridge arm circuit 2. Correspondingly, the lower bridge transfer circuit 4 can be connected to either the lower bridge arm circuit 2 or the upper bridge arm circuit 1. It should be noted that when the upper bridge transfer circuit 3 is connected to the upper bridge arm circuit 1, the lower bridge transfer circuit 4 is connected to the lower bridge arm circuit 2; conversely, when the upper bridge transfer circuit 3 is connected to the lower bridge arm circuit 2, the lower bridge transfer circuit 4 is connected to the upper bridge arm circuit 1.

[0099] Please continue reading. Figure 5Taking phase A as an example, one end of the upper bridge transfer circuit 3 is connected between the first half-control valve V45 and the second half-control valve V46, and one end of the lower bridge transfer circuit 4 is connected between the third half-control valve V15 and the fourth half-control valve V16.

[0100] The controllable shutdown hybrid grid commutation converter proposed in this application can transfer current from the bridge arm circuit to the auxiliary circuit by controlling the conduction of the transfer circuit, isolation circuit and full bridge circuit of the corresponding phase to form a parallel current with the bridge arm circuit, and controlling the first fully controlled valve in the main circuit to turn off to provide commutation voltage. When the half-controlled valve unit of the bridge arm circuit is turned off again, the commutation voltage is generated by the full bridge circuit and / or isolation circuit to transfer the current to another phase, thus realizing controllable commutation operation independent of AC voltage.

[0101] This application's embodiments effectively solve the commutation failure problem, enabling the controllable shutdown hybrid grid commutation converter to achieve controllable shutdown. During a fault, reactive power consumption can be reduced by decreasing the shutdown angle. If the fully controlled valve unit and / or full-bridge circuit in the bridge arm circuit are continuously shut down in steady state, the shutdown angle or trigger angle reference value can be reduced, thereby reducing reactive power consumption. Since the auxiliary circuit of the controllable shutdown hybrid grid commutation converter in this application's embodiments is configured with only one full-bridge circuit, and multiple bridge arm circuits share one full-bridge circuit, the cost of high-voltage direct current transmission systems with controllable shutdown capability is reduced, and the converter reliability is improved.

[0102] The first fully controlled valve, the first partially controlled valve, and the second partially controlled valve in the upper bridge arm circuit 1, as well as the second fully controlled valve, the third partially controlled valve, and the fourth partially controlled valve in the lower bridge arm circuit 2, can all be turned on or off under the control of a control signal. For example, a partially controlled valve can be a complete electromechanical module comprising dozens to hundreds of thyristor stages connected in series, and integrating auxiliary equipment such as damping circuits, voltage equalizing resistors, reactors, surge arresters, cooling interfaces, and monitoring interfaces. In a three-phase bridge arm circuit, six partially controlled valves constitute the converter valve, with each bridge arm circuit including one fully controlled valve and two partially controlled valves. The converter valve can operate in rectification mode to convert AC to DC, or in inverter mode to convert DC to AC.

[0103] Please see Figure 6 , Figure 6 This is a topology diagram of another controllable shutdown hybrid grid commutator provided in the embodiments of this application. Figure 6 and Figure 5 They are basically the same, the difference lies in Figure 6The upper bridge transfer circuit 3 is connected to the lower bridge arm circuit 2, and the lower bridge transfer circuit 4 is connected to the upper bridge arm circuit 1. For example, one end of the third valve unit V43 is connected to the transfer anode connection line P2, and the other end is connected between the third semi-controlled valve V15 and the fourth semi-controlled valve V16. One end of the fourth valve unit V13 is connected to the transfer cathode connection line N2, and the other end is connected between the first semi-controlled valve V45 and the second semi-controlled valve V46. The connection method and structure of the B-phase bridge arm circuit and the C-phase bridge arm circuit are similar to those of the A-phase bridge arm circuit, and will not be described again here.

[0104] Please see Figure 7 , Figure 7 This is a topology diagram of another controllable shutdown hybrid grid commutator provided in the embodiments of this application. Figure 7 and Figure 5 They are basically the same, the difference lies in Figure 7 The bridge arm circuit consists of a first semi-controlled valve, a second semi-controlled valve, and a first fully controlled valve connected in series. The other end of the transfer circuit is connected between the two semi-controlled valves. Taking phase A as an example, the upper bridge arm circuit 1 of phase A includes a first semi-controlled valve V45, a second semi-controlled valve V46, and a first fully controlled valve V44 connected in series. One end of the first semi-controlled valve V45 is connected to the anode bus P1. The lower bridge arm circuit 2 includes a third semi-controlled valve V15, a fourth semi-controlled valve V16, and a second fully controlled valve V14 connected in series. One end of the third semi-controlled valve V15 is connected to the cathode bus N1. The connection method and structure of the bridge arm circuits of phase B and phase C are similar to those of phase A, and will not be described in detail here.

[0105] Please continue reading. Figure 7 ,and Figure 6 Similarly, the upper bridge transfer circuit 3 of phase A is connected to the lower bridge arm circuit 2, and the lower bridge transfer circuit 4 of phase A is connected to the upper bridge arm circuit 1. For example, one end of the third valve unit V43 is connected to the transfer anode connection line P2, and the other end is connected between the third semi-controlled valve V15 and the fourth semi-controlled valve V16. One end of the fourth valve unit V13 is connected to the transfer cathode connection line N2, and the other end is connected between the first semi-controlled valve V45 and the second semi-controlled valve V46. The connection method and structure of the phase B bridge arm circuit and the phase C bridge arm circuit are similar to those of the phase A bridge arm circuit, and will not be described again here.

[0106] It should be noted that, Figure 7The positions of the first fully controlled valve and the second partially controlled valve can be interchanged, as can the positions of the second fully controlled valve and the fourth partially controlled valve. Taking phase A as an example, the upper bridge arm circuit 1 of phase A can also include a first partially controlled valve V45, a first fully controlled valve V44, and a second partially controlled valve V46 connected in series. One end of the first partially controlled valve V45 is connected to the anode bus P1. The lower bridge arm circuit 2 includes a third partially controlled valve V15, a second fully controlled valve V14, and a fourth partially controlled valve V16 connected in series. One end of the third partially controlled valve V15 is connected to the cathode bus N1; correspondingly, the other end of the third valve unit V43 is connected between the third partially controlled valve V15 and the second fully controlled valve V14, and the other end of the fourth valve unit V13 is connected between the first partially controlled valve V45 and the first fully controlled valve V44. The bridge arm circuits of phase B and phase C are similar to those of phase A, and will not be described in detail here.

[0107] In some embodiments, the upper arm circuit further includes a fifth semi-controlled valve, with the first fully controlled valve connected in parallel with the fifth semi-controlled valve, and the lower arm circuit further includes a sixth semi-controlled valve, with the second fully controlled valve connected in parallel with the sixth semi-controlled valve.

[0108] In some embodiments, the upper arm circuit further includes an eighth valve unit, wherein the first fully controlled valve is connected in series with the eighth valve unit and then connected in parallel with the fifth partially controlled valve; the lower arm circuit further includes a ninth valve unit, wherein the second fully controlled valve is connected in series with the ninth valve unit and then connected in parallel with the sixth partially controlled valve; wherein the eighth valve unit includes an uncontrolled valve and / or a partially controlled valve; and the ninth valve unit includes an uncontrolled valve and / or a partially controlled valve.

[0109] Please see Figure 8 , Figure 8 This is a schematic diagram of another controllable shutdown hybrid grid phase-commutation converter provided in an embodiment of this application. For example... Figure 8 As shown, in the A-phase bridge arm circuit, the first fully controlled valve V44 of the upper bridge arm circuit 1 is connected in series with the eighth valve unit V48, and then in parallel with the fifth partially controlled valve V47. The second fully controlled valve V17 of the lower bridge arm circuit 2 is connected in series with the ninth valve unit V18, and then in parallel with the sixth partially controlled valve V17. The eighth valve unit V48 includes uncontrolled valves and / or partially controlled valves, and the ninth valve unit V18 includes uncontrolled valves and / or partially controlled valves.

[0110] by Figure 8Taking the A-phase bridge arm circuit as an example, the upper bridge arm circuit 1 includes a first fully controlled valve unit V44, an eighth valve unit V48, a first semi-controlled valve V45, a second semi-controlled valve V46, and a fifth semi-controlled valve V47. The first fully controlled valve V44 and the eighth valve unit V48 are connected in series, and then connected in parallel with the fifth semi-controlled valve V47. After the parallel connection, they are connected in series with the first semi-controlled valve V45 and the second semi-controlled valve V46. The A-phase lower bridge arm circuit 2 includes a second fully controlled valve V14, a ninth valve unit V18, a third semi-controlled valve V15, a fourth semi-controlled valve V16, and a sixth semi-controlled valve V17. The second fully controlled valve V14 and the ninth valve unit V18 are connected in series, and then connected in parallel with the sixth semi-controlled valve V17. After the parallel connection, they are connected in series with the third semi-controlled valve V15 and the fourth semi-controlled valve V16. One end of the first fully controlled valve V44 is connected to the anode bus P1, and one end of the second semi-controlled valve V46 is connected to the A-phase lower bridge arm circuit 2. One end of the second fully controlled valve V14 is connected to the cathode bus N1, and one end of the fourth semi-controlled valve V16 is connected to the upper bridge arm circuit 1 of phase A. The connection method and structure of the bridge arm circuits of phase B and phase C are similar to those of the bridge arm circuit of phase A, and will not be described in detail here.

[0111] In some embodiments, the pressure resistance ratio of the first semi-controlled valve and the second semi-controlled valve ranges from 0.1 to 10; the pressure resistance ratio of the third semi-controlled valve and the fourth semi-controlled valve ranges from 0.1 to 10.

[0112] The withstand voltage ratio of the first and second semi-controlled valves represents the ratio of the maximum voltage values ​​that the two semi-controlled valves can withstand. Similarly, the withstand voltage ratio of the third and fourth semi-controlled valves represents the ratio of the maximum voltage values ​​that the two semi-controlled valves can withstand. In practical applications, the withstand voltage values ​​of the first, second, third, and fourth semi-controlled valves must meet the system's rated voltage and overvoltage requirements to ensure reliable operation under various conditions. The withstand voltage ratio of the first and second semi-controlled valves indicates the voltage distribution between them, as does the withstand voltage ratio of the third and fourth semi-controlled valves. Generally, a single valve with a higher withstand voltage can withstand a higher voltage.

[0113] Please continue reading. Figure 5 Taking the A-phase bridge arm circuit as an example, the withstand voltage ratio of the first half-controlled valve V4 and the second half-controlled valve V46 in the A-phase upper bridge arm circuit 1 ranges from 0.1 to 10, meaning the ratio of the withstand voltage ratio of the first half-controlled valve V45 to the withstand voltage ratio of the second half-controlled valve V46 is within the range of 0.1 to 10. It can be understood that the withstand voltage ratio range of the first and second half-controlled valves in the B-phase or C-phase upper bridge arm circuit is similar to that in the A-phase upper bridge arm circuit described above. Similarly, the withstand voltage ratios of the third and fourth half-controlled valves in the A-phase, B-phase, or C-phase lower bridge arm circuit 2 are similar to those in the A-phase upper bridge arm circuit described above, and will not be elaborated upon here. When an AC system fault occurs, approximately the rated bridge arm voltage (approximately 0.6 times the maximum bridge arm voltage) is required to achieve reliable commutation. The first half-controlled valve needs to have a voltage greater than this. Therefore, in some implementations… Figure 5 The pressure resistance ratio of the first and second semi-control valves is 1.5, and the pressure resistance ratio of the third and fourth semi-control valves is also 1.5. In some implementations, Figure 6 The first or third semi-controlled valve is mainly used to prevent follow-through after forced commutation during a fault. Its maximum voltage value can be selected to be relatively low. Preferably, the withstand voltage ratio of the first and second semi-controlled valves is 0.2, and the withstand voltage ratio of the third and fourth semi-controlled valves is 0.2.

[0114] In some embodiments, the upper bridge isolation circuit 5 includes a fifth valve unit, and the lower bridge isolation circuit 6 includes a sixth valve unit. The single valve of the fifth valve unit and / or the sixth valve unit includes at least one of the following: a fully controlled valve, a partially controlled valve, and a non-controlled valve.

[0115] The fifth valve unit controls the on / off state of the upper bridge isolation circuit 5, and the sixth valve unit controls the on / off state of the lower bridge isolation circuit 6. The auxiliary circuit can achieve current flow through the upper bridge isolation circuit 5 or the lower bridge isolation circuit 6 in the event of a commutation failure in the bridge arm circuit, by controlling the orderly on / off state of the fifth and / or sixth valve units. Each valve in the fifth or sixth valve unit can be a fully controlled valve, a partially controlled valve, or an uncontrolled valve.

[0116] For example, a semi-controlled valve refers to a semiconductor device that achieves partial control functionality through an external control signal. For instance, a semi-controlled valve can be turned on by an external control signal, but its turning off depends on the characteristics of the device itself. An uncontrolled valve refers to a device whose on or off state cannot be determined by an external control signal, such as an uncontrolled switch or diode.

[0117] Please continue reading. Figure 1 The single valve of the fifth valve unit of the upper bridge isolation circuit 5 can be identified as V71, and the single valve of the sixth valve unit of the lower bridge isolation circuit 6 can be identified as V72. One end of the single valve V71 is connected to the anode bus P1, and the other end is connected to one end of the full bridge circuit. The other end of the full bridge circuit is connected to one end of the single valve V72, and the other end of the single valve V72 is connected to the cathode bus N1.

[0118] In some embodiments, the upper bridge isolation circuit 5 further includes a first disconnect switch or a first disconnector, and the lower bridge isolation circuit 6 further includes a second disconnect switch or a second disconnector. The fifth valve unit is connected to the anode bus via the first disconnect switch or the first disconnector, and the sixth valve unit is connected to the cathode bus via the second disconnect switch or the second disconnector.

[0119] The first disconnecting switch or the first disconnecting switch is used to connect the fifth valve unit of the upper bridge isolation circuit 5 and the anode bus P1, and the second disconnecting switch or the second disconnecting switch is used to connect the sixth valve unit of the lower bridge isolation circuit 6 and the cathode bus N1. In this embodiment, the upper bridge isolation circuit 5 or the lower bridge isolation circuit 6 is accessed by controlling the first disconnecting switch or the first disconnecting switch, as well as the second disconnecting switch and the second disconnecting switch.

[0120] In some embodiments, the upper bridge isolation circuit further includes a third disconnecting switch or a third disconnector, and the lower bridge isolation circuit further includes a fourth disconnecting switch or a fourth disconnector; the fifth valve unit of the upper bridge isolation circuit is connected in parallel with the third disconnecting switch or the third disconnector, and the sixth valve unit of the lower bridge isolation circuit is connected in parallel with the fourth disconnecting switch or the fourth disconnector. Figure 5 For example, in one embodiment, the third disconnector or third disconnector and the fourth disconnector or fourth disconnector can be closed to achieve the conversion from inverter operation to rectifier operation by reversing the DC current, without needing to reverse the voltage polarity.

[0121] In some embodiments, the semi-controlled valve includes a one-way semi-controlled switch or a two-way semi-controlled switch. The one-way semi-controlled switch includes a plurality of semi-controlled devices connected in series. The two-way semi-controlled switch includes a plurality of first semi-controlled units connected in series, each first semi-controlled unit including a plurality of anti-parallel semi-controlled devices. Alternatively, the two-way semi-controlled switch includes a plurality of anti-parallel second semi-controlled units, each second semi-controlled unit including a plurality of semi-controlled devices connected in series.

[0122] Reverse parallel connection refers to connecting semi-controlled devices together in parallel with opposite polarities to achieve freewheeling protection and bidirectional conduction. Both unidirectional and bidirectional semi-controlled switches can include several semi-controlled devices. In a unidirectional semi-controlled switch, several semi-controlled devices are connected in series. In a bidirectional semi-controlled switch, semi-controlled devices are first connected in reverse parallel to form several first semi-controlled units, and then these first semi-controlled units are connected in series to form the switch. A bidirectional semi-controlled switch can also be formed by first connecting semi-controlled devices in series to form several second semi-controlled units, and then these second semi-controlled units are connected in reverse parallel to form the switch. For example, the semi-controlled device can be a semiconductor device that can be controlled to turn on but not controlled to turn off, such as a thyristor.

[0123] In some embodiments, the uncontrolled valve includes a plurality of uncontrolled devices connected in series.

[0124] Uncontrolled devices are semiconductor devices that cannot be controlled to turn on or off, such as diodes.

[0125] In some embodiments, the self-commutated converter further includes a first surge arrester, which is connected in parallel with at least one of the following single valves: a single valve in a first valve unit, a single valve in a second valve unit, a single valve in a third valve unit, a single valve in a fourth valve unit, a single valve in a fifth valve unit, and a single valve in a sixth valve unit.

[0126] In the self-commutated converter of this application embodiment, the single valve includes an overvoltage-sensitive semiconductor device. Connecting the first surge arrester in parallel with the single valve can prevent the single valve from being damaged by overvoltage. When an overvoltage occurs in the circuit, the first surge arrester will quickly conduct to discharge the overvoltage, thereby limiting the amplitude of the overvoltage and protecting the single valve.

[0127] In some embodiments, the full-bridge circuit 7 includes a seventh valve unit. The seventh valve unit includes a fully controlled valve.

[0128] A fully controllable valve is a device that can be controlled to either turn on or off via an external control signal. The seventh valve unit of the full-bridge circuit 7 is equipped with a fully controllable valve, giving the full-bridge circuit 7 greater flexibility and control capabilities. Please continue reading. Figure 1 The seventh valve unit in the full-bridge circuit 7 includes a full control valve V81, one end of which is connected to the transfer anode connection line P2 and the other end is connected to the transfer cathode connection line N2.

[0129] In some embodiments, the full-bridge circuit 7 further includes a resistor unit or an inductor unit, which is connected in series with the seventh valve unit. Connecting the resistor unit to the seventh valve unit in this embodiment prevents excessive current flowing through the seventh valve unit from damaging the device; connecting the inductor unit to the seventh valve unit smooths the current, reduces transient current changes, and thus reduces electromagnetic interference.

[0130] In some embodiments, the total control valve includes a one-way total control switch, and / or a two-way total control switch, and / or a module series switch. The one-way total control switch includes a plurality of one-way total control devices connected in series. The two-way total control switch includes a plurality of two-way total control devices or a two-way total control module connected in series. The module series switch includes a plurality of total control sub-modules connected in series.

[0131] Unidirectional fully controllable devices refer to semiconductor devices with unidirectional controllable turn-off and turn-on capabilities. Unidirectional fully controllable devices include, but are not limited to, insulated-gate bipolar transistors (IGBTs), integrated-gate commutated thyristors (IGCTs), reverse-resistance IGCTs, gate turn-off thyristors (GTOs), and metal-oxide-semiconductor field-effect transistors (MOSFETs).

[0132] A bidirectional fully controllable device refers to a semiconductor device with bidirectional controllable turn-off and turn-on capabilities. A bidirectional fully controllable module refers to a module with bidirectional controllable turn-off and turn-on capabilities. Bidirectional fully controllable devices include, but are not limited to, anti-parallel reverse-resistance IGCTs and anti-series IGBTs.

[0133] In some embodiments, the fully controlled submodule includes at least one of the following: a half-bridge submodule, a full-bridge submodule, a quasi-full-bridge submodule, a midpoint clamping submodule, a dual half-bridge series submodule, a dual full-bridge series submodule, a clamping dual submodule, a cross-connected dual submodule, a self-resisting submodule, or a diode clamping submodule. The semiconductor devices in the fully controlled submodule include, but are not limited to, IGBTs and IGCTs.

[0134] In some embodiments, the fully controlled submodule includes a capacitor and / or a battery. The capacitor may be a supercapacitor. The fully controlled submodule stores energy through the capacitor and / or battery, enabling energy exchange when there is no power supply to the anode and cathode buses. For example, controlling the main circuit inverter operation allows the energy from the fully controlled submodule to be output to the AC side of the power transmission system.

[0135] In some embodiments, the full-bridge circuit further includes a second surge arrester, which is connected in parallel with the full control valve, a plurality of unidirectional full control devices, a plurality of bidirectional full control devices, a plurality of bidirectional full control modules, or a plurality of full control sub-modules.

[0136] The second surge arrester, connected in parallel with a fully controlled valve, several unidirectional fully controlled devices, several bidirectional fully controlled devices, several bidirectional fully controlled modules, or several fully controlled sub-modules, can prevent related semiconductor devices from being damaged by overvoltage. When an overvoltage occurs in the circuit, the second surge arrester will quickly conduct, discharging the overvoltage and thus limiting the amplitude of the overvoltage, achieving a protective effect.

[0137] The structure of the valve unit provided in the embodiments of this application will be described below.

[0138] Figure 9 Image (a) is a schematic diagram of an uncontrolled valve. For example... Figure 9 As shown in (a), the uncontrolled device is a diode, and the uncontrolled valve includes uncontrolled devices connected in series, that is, it includes diodes connected in series. At this time, the valve unit cannot be controlled to open or close by an external signal. Due to the unidirectional conduction of the diode, the valve unit has unidirectional current-carrying capability and unidirectional voltage-blocking capability.

[0139] Figure 9 Figure (b) is a schematic diagram of a semi-controlled valve. For example... Figure 9As shown in (b), the semi-controlled device is a thyristor, and the semi-controlled valve is a one-way semi-controlled switch. The one-way semi-controlled switch includes a series-connected semi-controlled device, namely a series-connected thyristor. In this case, the valve unit can be controlled to turn on by an external signal, but cannot be controlled to turn off, possessing unidirectional current-carrying capability and bidirectional voltage-blocking capability. In some implementations, the one-way semi-controlled switch can also be composed of a thyristor and a diode connected in series.

[0140] Figure 9 Figure (c) is a schematic diagram of a semi-controlled valve. For example... Figure 9 As shown in (c), the semi-controlled valve is a bidirectional semi-controlled switch, which is formed by first connecting thyristors in reverse parallel and then in series. In this case, the valve unit can be controlled to turn on by an external signal, but cannot be controlled to turn off, and has bidirectional current-carrying capability and bidirectional voltage-blocking capability.

[0141] Figure 9 Figure (d) shows a schematic diagram of the connection between a semi-controlled valve and a non-controlled valve. For example... Figure 9 As shown in (d), the semi-controlled valve and the uncontrolled valve are connected in anti-parallel, that is, the thyristor and the diode are connected in anti-parallel and then in series. At this time, the valve unit can be controlled to conduct in one direction by an external signal, but cannot be controlled to turn off, and has bidirectional current carrying capacity and unidirectional voltage blocking capacity.

[0142] Figure 9 Image (e) is a schematic diagram of a fully controllable valve. For example... Figure 9 As shown in (e), the fully controlled valve is a one-way fully controlled switch, including an IGBT module connected in series. The IGBT module includes an IGBT and a diode connected in anti-parallel. The valve unit can be controlled by an external signal to unidirectionally open and close, possessing bidirectional current-carrying and unidirectional voltage-blocking capabilities.

[0143] Figure 9 Figure (f) is a schematic diagram of a fully controllable valve. For example... Figure 9 As shown in (f), the fully controlled valve is a one-way fully controlled switch, including a series-connected reverse-resistance IGCT. In this case, the valve unit can be controlled by an external signal to unidirectionally open and close, possessing unidirectional current-carrying and bidirectional voltage-blocking capabilities.

[0144] Figure 9 Figure (g) is a schematic diagram of a fully controllable valve. For example... Figure 9 As shown in (g), the fully controlled valve is a one-way fully controlled switch, comprising an IGBT module and a diode connected in series. In this case, the valve unit can be controlled by an external signal to unidirectionally open and close, possessing unidirectional current-carrying and bidirectional voltage-blocking capabilities.

[0145] Figure 9 The diagram in image (h) is a schematic of a fully controllable valve. For example... Figure 9As shown in (h), the fully controlled valve is a one-way fully controlled switch, consisting of a reverse-resistance IGCT and a thyristor. The reverse-resistance IGCT and the thyristor are connected in anti-parallel and then in series. The valve unit can be controlled by an external signal to open in both directions and close in one direction, possessing bidirectional current-carrying and bidirectional voltage-blocking capabilities.

[0146] Figure 9 Figure (i) is a schematic diagram of a fully controllable valve. For example... Figure 9 As shown in (i), the fully controlled valve is a bidirectional fully controlled switch, comprising a forward IGBT module and a reverse IGBT module connected in series. The valve unit can be controlled bidirectionally to open and close via an external signal, possessing both bidirectional current-carrying capability and bidirectional voltage-blocking capability.

[0147] Figure 9 Figure (j) is a schematic diagram of a fully controllable valve. For example... Figure 9 As shown in (j), the fully controlled valve is a bidirectional fully controlled switch, including a reverse-resistance type IGCT. Different reverse-resistance type IGCTs are connected in anti-parallel and then in series. At this time, the valve unit can be controlled to open and close bidirectionally by an external signal, and has bidirectional current-carrying capability and bidirectional voltage-blocking capability.

[0148] Figure 9 The diagram in Figure (k) is a schematic of a fully controllable valve. For example... Figure 9 As shown in diagram (k), the fully controlled valve is a modular series switch, comprising a series-connected half-bridge sub-module. Each half-bridge sub-module includes two IGBT modules, and the series-connected switch also includes a capacitor. The connection point of the two IGBT modules serves as the positive terminal of the half-bridge sub-module, while the other end of one IGBT module serves as the negative terminal. The two IGBT modules are connected in series and then in parallel with the capacitor. This valve unit can be controlled by an external signal to unidirectionally open and close, possessing bidirectional current-carrying capability and unidirectional voltage-blocking capability.

[0149] Figure 9 Figure (l) is a schematic diagram of a fully controllable valve. For example... Figure 9 As shown in Figure (l), the fully controlled valve is a modular series switch, comprising a series-connected full-bridge sub-module. Each full-bridge sub-module includes four IGBT modules, which are connected in series in pairs and then in parallel. These series-connected IGBT modules are then connected in parallel with a capacitor. The connection points of the series-connected IGBT modules serve as the positive and negative terminals of the full-bridge sub-module, respectively. The valve unit can then be controlled bidirectionally to open and close via an external signal, possessing both bidirectional current-carrying and bidirectional voltage-blocking capabilities.

[0150] Figure 9 The diagram (m) shows a fully controllable valve. For example... Figure 9As shown in Figure (m), the fully controlled valve is a modular series switch, comprising a series-connected quasi-full-bridge sub-module. Each quasi-full-bridge sub-module includes two IGBT modules and two diodes, connected in series and then in parallel. The series-connected IGBT modules and diodes are then connected in parallel with a capacitor. The connection points of the series-connected IGBT modules and diodes serve as the positive and negative terminals of the quasi-full-bridge sub-module, respectively. The valve unit can then be controlled by an external signal to unidirectionally open and close, possessing bidirectional current-carrying capability and bidirectional voltage-blocking capability.

[0151] Figure 10A Specifically for Figure 9 The full-bridge submodule in (l) will be explained. Figure 10B Specifically for Figure 9 The full-bridge submodule in (m) will be described.

[0152] Please see Figure 10A The full-bridge submodule comprises four IGBT modules and a capacitor C1. The IGBT modules are designated M1, M2, M3, and M4. Each IGBT module includes an anti-parallel IGBT (T1) and a diode D1. The series-connected IGBT modules M1 and M2 are connected in parallel with the series-connected IGBT modules M3 and M4. The series-connected IGBT modules M1 and M2 are also connected in parallel with capacitor C1. In this full-bridge submodule, the connection point of the series-connected IGBT modules M1 and M2 is used as the positive terminal, and the connection point of the series-connected IGBT modules M3 and M4 is used as the negative terminal. When current flows through IGBT modules M1 and M4, the full-bridge submodule provides a positive voltage; when current flows through IGBT modules M2 and M3, the full-bridge submodule provides a negative voltage.

[0153] Please see Figure 10B The quasi-full-bridge submodule includes two IGBT modules M5 and M6, two diodes D2 and D3, and a capacitor C2. The IGBT module comprises anti-parallel IGBTs and diodes, with diode D2 and IGBT module M5 connected in series, and IGBT module M6 and diode D3 connected in parallel. Diode D2 and IGBT module M5 are also connected in parallel with capacitor C2. In this quasi-full-bridge submodule, the connection point of diode D2 and IGBT module M5 in series serves as the positive terminal, and the connection point of diode D3 and IGBT module M6 in series serves as the negative terminal. When current flows through diodes D2 and D3, the quasi-full-bridge submodule provides a positive voltage; when current flows through IGBT modules M5 and M6, it provides a negative voltage.

[0154] In some embodiments, the IGBT module in the above sub-modules can also be an IGCT module.

[0155] In some embodiments, the IGBT module is further configured with a corresponding drive circuit and a buffer circuit. The drive circuit is used to control the IGBT module to turn on or off, and the buffer circuit is used to protect the IGBT module. For example, the buffer circuit may include a capacitor, or a resistor and a capacitor connected in series.

[0156] In some embodiments, the common terminal of the upper bridge arm circuit 1 and the lower bridge arm circuit 2 serves as the phase output terminal and is connected to the AC system through a transformer or reactor.

[0157] Please continue reading. Figure 1 The common terminal of the upper bridge arm circuit 1 and the lower bridge arm circuit 2 serves as the phase output terminal, used to connect to each phase of AC power. For example, the common terminal of the upper bridge arm circuit 1 and the lower bridge arm circuit 2 of phase A is used as the phase A output terminal and connected to the phase A AC power; the common terminal of the upper bridge arm circuit 1 and the lower bridge arm circuit 2 of phase B is used as the phase B output terminal and connected to the phase B AC power; and the common terminal of the upper bridge arm circuit 1 and the lower bridge arm circuit 2 of phase C is used as the phase C output terminal and connected to the phase C AC power.

[0158] In some embodiments, the converter further includes a voltage source converter. When the main circuit includes a three-phase bridge arm circuit, the voltage source converter uses a three-phase star or delta connection, connected in parallel with the three phases of the main circuit at their respective output terminals. The voltage source converter is used for reactive power compensation or harmonic filtering. The voltage source converter includes a reactor or a transformer.

[0159] A three-phase star connection means that the ends of the three-phase windings are connected to the neutral point, and the beginnings are connected to the three-phase AC power supply respectively. A three-phase delta connection means that the three-phase windings are connected end to end to form a closed delta. In this embodiment, a voltage source converter is connected in parallel at the phase output end. The voltage source converter and the self-commutated converter jointly output electrical energy. The voltage source converter can compensate for reactive power and filter harmonics for the self-commutated converter, thereby improving the performance of the self-commutated converter and the quality of the output power.

[0160] In some embodiments, the converter further includes an energy storage circuit, one end of which is connected to the anode bus and the other end of which is connected to the cathode bus; wherein the energy storage circuit includes a module series switch.

[0161] Energy storage circuits can store electrical energy using energy storage elements in a series-connected modular switch. These energy storage elements include supercapacitors or batteries. In the absence of power to the anode and cathode buses, energy exchange can be achieved using the stored energy. For example, controlling a self-commutated converter to output energy from the energy storage circuit to the AC side of the converter.

[0162] The following is combined with Figure 9 Middle (a) to Figure 9The structural schematic diagram of the valve unit shown in Figure (m) provides a detailed description of the circuit diagram of the self-commutated converter in this embodiment of the application.

[0163] Figure 11 This is a circuit diagram of a self-commutated converter provided in an embodiment of this application, and... Figure 1 The corresponding topological structure. For example... Figure 11 As shown, in the main circuit, phase A upper bridge arm circuit 1 includes a semi-controlled valve V41, phase B upper bridge arm circuit 1 includes a semi-controlled valve V61, phase C upper bridge arm circuit 1 includes a semi-controlled valve V21, phase A lower bridge arm circuit 2 includes a semi-controlled valve V11, phase B lower bridge arm circuit 2 includes a semi-controlled valve V31, and phase C lower bridge arm circuit 2 includes a semi-controlled valve V51. The auxiliary circuit's phase A upper bridge transfer circuit 3 includes a semi-controlled valve V43, phase B upper bridge transfer circuit 3 includes a semi-controlled valve V63, and phase C upper bridge transfer circuit 3 includes a semi-controlled valve V23. One end of each upper bridge transfer circuit 3 is connected to the transfer anode connection line P2, and the other end is connected to the corresponding phase's upper bridge arm circuit 1. Phase A downbridge transfer circuit 4 includes a semi-controlled valve V13, Phase B downbridge transfer circuit 4 includes a semi-controlled valve V33, and Phase C downbridge transfer circuit 4 includes a semi-controlled valve V53. One end of each downbridge transfer circuit 4 is connected to the transfer cathode connection line N2, and the other end is connected to the corresponding phase downbridge arm circuit 2. Upper bridge isolation circuit 5 includes a semi-controlled valve V71, and lower bridge isolation circuit 6 includes a semi-controlled valve V72. All of the above semi-controlled valves include... Figure 9 The unidirectional semi-controlled switch shown in (b) is a series-connected thyristor. The full-bridge circuit 7 includes a fully controlled valve V81; the fully controlled valve includes, for example... Figure 9 The module series switch shown in (l) is a full-bridge sub-module connected in series.

[0164] Figure 12 This is a circuit diagram of a self-commutated converter provided in an embodiment of this application, and... Figure 2 The corresponding topological structure. Figure 12 and Figure 11 The circuit diagrams are largely the same, the difference being that... Figure 12 In the main circuit, phase A upper bridge arm circuit 1 includes semi-controlled valves V41 and V42; phase B upper bridge arm circuit 1 includes semi-controlled valves V61 and V62; phase C upper bridge arm circuit 1 includes semi-controlled valves V21 and V22; phase A lower bridge arm circuit 2 includes semi-controlled valves V11 and V12; phase B lower bridge arm circuit 2 includes semi-controlled valves V31 and V32; and phase C lower bridge arm circuit 2 includes semi-controlled valves V51 and V52. In the auxiliary circuit, one end of each phase upper bridge transfer circuit 3 is connected to the transfer anode connection line P2, and the other end is connected between the two semi-controlled valves of the corresponding phase upper bridge arm circuit 1. One end of each phase lower bridge transfer circuit 4 is connected to the transfer cathode connection line N2, and the other end is connected between the two semi-controlled valves of the corresponding phase lower bridge arm circuit 2.

[0165] Figure 13 This is a circuit diagram of a self-commutated converter provided in an embodiment of this application, and... Figure 3 The corresponding topological structure. Figure 13 and Figure 11 The circuit diagrams are largely the same, the difference being that... Figure 13 In the auxiliary circuit, one end of the upper bridge transfer circuit 3 of each phase is connected to the transfer anode connection line P2, and the other end is connected to the lower bridge arm circuit of the corresponding phase. One end of the lower bridge transfer circuit 4 of each phase is connected to the transfer cathode connection line N2, and the other end is connected to the upper bridge arm circuit of the corresponding phase.

[0166] Figure 14 This is a circuit diagram of a self-commutated converter provided in an embodiment of this application, and... Figure 4 The corresponding topological structure. Figure 14 and Figure 13 The circuit diagrams are largely the same, the difference being that... Figure 14 In the main circuit, phase A upper bridge arm circuit 1 includes semi-controlled valves V41 and V42; phase B upper bridge arm circuit 1 includes semi-controlled valves V61 and V62; phase C upper bridge arm circuit 1 includes semi-controlled valves V21 and V22; phase A lower bridge arm circuit 2 includes semi-controlled valves V11 and V12; phase B lower bridge arm circuit 2 includes semi-controlled valves V31 and V32; and phase C lower bridge arm circuit 2 includes semi-controlled valves V51 and V52. Semi-controlled valves V41, V61, V21, V11, V31, and V51 each include... Figure 9 The one-way semi-controlled switch shown in (b) is a series-connected thyristor. Semi-controlled valves V42, V62, V22, V12, V32, and V52 all include the following... Figure 9 The bidirectional semi-controlled switch shown in (c) is formed by first connecting thyristors in reverse parallel and then in series. In this case, one end of the upper bridge transfer circuit 3 of each phase of the auxiliary circuit is connected to the transfer anode connection line P2, and the other end is connected between the two semi-controlled valves of the lower bridge arm circuit of the corresponding phase. One end of the lower bridge transfer circuit 4 of each phase is connected to the transfer cathode connection line N2, and the other end is connected between the two semi-controlled valves of the upper bridge arm circuit of the corresponding phase.

[0167] Figure 15 This is a circuit diagram of a self-commutated converter provided in an embodiment of this application, and... Figure 1 The corresponding topological structure. Figure 15 and Figure 11 The circuit diagrams are largely the same, the difference being that... Figure 15 In the auxiliary circuit, the upper bridge isolation circuit 5 includes a semi-controlled valve V71, and the lower bridge isolation circuit 6 includes a semi-controlled valve V72; both the semi-controlled valves V71 and V72 include the following... Figure 9 The bidirectional semi-controlled switch shown in (c) is formed by first connecting thyristors in reverse parallel and then in series. The above structure enables the full-bridge circuit 7 to provide DC power, which is then inverted to the AC side by the main circuit.

[0168] Figure 16 This is a circuit diagram of a self-commutated converter provided in an embodiment of this application, and... Figure 2 The corresponding topological structure. Figure 16 and Figure 12 The circuit diagrams are largely the same, the difference being that... Figure 16 In the auxiliary circuit, the full-bridge circuit 7 includes a full-control valve V81; the full-control valve V81 includes, for example,... Figure 9 The one-way fully controllable switch shown in (e) and as shown in the figure Figure 9 The module series switch shown in Figure (l) consists of a unidirectional fully controlled switch and a module series switch connected in series. The unidirectional fully controlled switch includes IGBTs connected in series, and a surge arrester F81 is connected in parallel with the unidirectional fully controlled switch. The module series switch includes full-bridge sub-modules connected in series. During steady-state operation, the module series switch provides a relatively small commutation voltage, reducing the turn-off angle or firing angle, improving the power factor, and reducing reactive power consumption. During AC faults, the unidirectional fully controlled switch provides a larger commutation voltage, suppressing commutation failure or further reducing reactive power consumption during faults.

[0169] The following is combined with Figure 9 Middle (a) to Figure 9 The structural schematic diagram of the valve unit shown in Figure (m) provides a detailed description of the circuit diagram of the controllable shut-off hybrid grid phase-commutation converter according to an embodiment of this application.

[0170] Please see Figure 17 , Figure 17 This is a circuit diagram of a controllable shutdown hybrid grid phase-commutation converter provided in an embodiment of this application. Figure 17 circuit and Figure 5 The corresponding topological structure. For example... Figure 17 As shown, the upper bridge arm circuit 1 of phase A includes a first fully controlled valve V44, a first partially controlled valve V45, and a second partially controlled valve V46 connected in series. The lower bridge arm circuit 2 of phase A includes a second fully controlled valve V14, a third partially controlled valve V15, and a fourth partially controlled valve V16 connected in series. One end of the first fully controlled valve V44 is connected to the anode bus P1, one end of the second partially controlled valve V46 is connected to the lower bridge arm circuit 2 of phase A, one end of the second fully controlled valve V14 is connected to the cathode bus N1, and one end of the fourth partially controlled valve V16 is connected to the upper bridge arm circuit 1 of phase A.

[0171] Phase B upper arm circuit 1 includes a first fully controlled valve V64, a first partially controlled valve V65, and a second partially controlled valve V66 connected in series. Phase B lower arm circuit 2 includes a second fully controlled valve V34, a third partially controlled valve V35, and a fourth partially controlled valve V36 connected in series. One end of the first fully controlled valve V64 is connected to the anode bus P1, one end of the second partially controlled valve V66 is connected to the phase B lower arm circuit 2, one end of the second fully controlled valve V34 is connected to the cathode bus N1, and one end of the fourth partially controlled valve V36 is connected to the phase B upper arm circuit 1.

[0172] The upper bridge arm circuit 1 of phase C includes a first fully controlled valve V24, a first partially controlled valve V25, and a second partially controlled valve V26 connected in series. The lower bridge arm circuit 2 of phase C includes a second fully controlled valve V54, a third partially controlled valve V55, and a fourth partially controlled valve V56 connected in series. One end of the first fully controlled valve V24 is connected to the anode bus P1, one end of the second partially controlled valve V26 is connected to the lower bridge arm circuit 2 of phase C, one end of the second fully controlled valve V54 is connected to the cathode bus N1, and one end of the fourth partially controlled valve V56 is connected to the upper bridge arm circuit 1 of phase C.

[0173] The upper bridge isolation circuit 5, the full bridge circuit 7, and the lower bridge isolation circuit 6 are connected in series. The upper bridge isolation circuit 5 includes a fifth valve unit V71, the lower bridge isolation circuit 6 includes a sixth valve unit V72, and the full bridge circuit 7 includes a seventh valve unit V81. One end of the fifth valve unit V71 is connected to the anode bus P1, and the other end is connected to the transfer cathode connection line N2. One end of the seventh valve unit V81 is connected to the transfer cathode connection line N2, and the other end is connected to the transfer anode connection line P2. One end of the sixth valve unit V72 is connected to the transfer anode connection line P2, and the other end is connected to the cathode bus N1.

[0174] Phase A upper bridge transfer circuit 3 includes a third valve unit V43, and phase A lower bridge transfer circuit 4 includes a fourth valve unit V13. One end of the third valve unit V43 is connected to the transfer anode connection line P2, and the other end is connected between the first semi-controlled valve V45 and the second semi-controlled valve V46. One end of the fourth valve unit V13 is connected to the transfer cathode connection line N2, and the other end is connected between the third semi-controlled valve V15 and the fourth semi-controlled valve V16.

[0175] Phase B upper bridge transfer circuit 3 includes a third valve unit V63, and phase B lower bridge transfer circuit 4 includes a fourth valve unit V33. One end of the third valve unit V63 is connected to the transfer anode connection line P2, and the other end is connected between the first semi-control valve V65 and the second semi-control valve V66. One end of the fourth valve unit V33 is connected to the transfer cathode connection line N2, and the other end is connected between the third semi-control valve V35 and the fourth semi-control valve V36.

[0176] The C-phase upper bridge transfer circuit 3 includes a third valve unit V23, and the C-phase lower bridge transfer circuit 4 includes a fourth valve unit V53. One end of the third valve unit V23 is connected to the transfer anode connection line P2, and the other end is connected between the first semi-controlled valve V25 and the second semi-controlled valve V26. One end of the fourth valve unit V53 is connected to the transfer cathode connection line N2, and the other end is connected between the third semi-controlled valve V55 and the fourth semi-controlled valve V56.

[0177] Figure 17 The first, second, third, fourth, third, fourth, fifth, and sixth valve units all employ the following... Figure 9 The unidirectional semi-controlled switch shown in (b) consists of thyristors connected in series. The cathode of the first semi-controlled valve is connected to the cathode of the third valve unit, and the anode of the third semi-controlled valve is connected to the anode of the fourth valve unit. The first fully controlled valve, the second fully controlled valve, and the seventh valve unit employ... Figure 9 The unidirectional fully controlled switch shown in (e) consists of IGBT modules connected in series.

[0178] In some implementations, if the maximum voltage value of each bridge arm circuit is 1.0 pu, then the maximum voltage values ​​of the first fully controlled valve, the first partially controlled valve, the second partially controlled valve, the third valve unit, the fifth valve unit, and the seventh valve unit are 0.1 pu, 0.6 pu, 0.4 pu, 0.6 pu, 0.6 pu, and 0.6 pu, respectively; and the maximum voltage values ​​of the second fully controlled valve, the third partially controlled valve, the fourth partially controlled valve, the fourth valve unit, the sixth valve unit, and the seventh valve unit are 0.1 pu, 0.6 pu, 0.4 pu, 0.6 pu, 0.6 pu, and 0.6 pu, respectively.

[0179] Please see Figure 18 , Figure 18 This is a circuit diagram of another controllable shutdown hybrid grid commutator provided in an embodiment of this application. Figure 18 Circuit diagram and Figure 6 The corresponding topological structure. Figure 18 and Figure 17 The circuit diagrams are largely the same, the difference being that... Figure 18 The other end of the upper bridge transfer circuit 3 is connected between the third and fourth half-control valves of the lower bridge arm circuit 2 of the corresponding phase. The other end of the lower bridge transfer circuit 4 is connected between the first and second half-control valves of the upper bridge arm circuit 1 of the corresponding phase.

[0180] For example, Figure 18One end of the third valve unit V43 of the upper bridge transfer circuit 3 of phase A is connected to the transfer anode connection line P2, and the other end is connected between the third semi-control valve V15 and the fourth semi-control valve V16. One end of the fourth valve unit V13 of the lower bridge transfer circuit 4 of phase A is connected to the transfer cathode connection line N2, and the other end is connected between the first semi-control valve V45 and the second semi-control valve V46.

[0181] One end of the third valve unit V63 of the B-phase upper bridge transfer circuit 3 is connected to the transfer anode connection line P2, and the other end is connected between the third semi-control valve V35 and the fourth semi-control valve V36. One end of the fourth valve unit V33 of the B-phase lower bridge transfer circuit 4 is connected to the transfer cathode connection line N2, and the other end is connected between the first semi-control valve V65 and the second semi-control valve V66.

[0182] One end of the third valve unit V23 of the C-phase upper bridge transfer circuit 3 is connected to the transfer anode connection line P2, and the other end is connected between the third semi-control valve V55 and the fourth semi-control valve V56. One end of the fourth valve unit V53 of the C-phase lower bridge transfer circuit 4 is connected to the transfer cathode connection line N2, and the other end is connected between the first semi-control valve V25 and the second semi-control valve V26.

[0183] The first semi-controlled valve, the third semi-controlled valve, the third valve unit, the fourth valve unit, the fifth valve unit, and the sixth valve unit all adopt the following... Figure 9 The unidirectional semi-controlled switch shown in (b) consists of thyristors connected in series. The second and fourth semi-controlled valves employ... Figure 9 The bidirectional semi-controlled switch shown in (c) consists of thyristors connected in reverse parallel and then in series. The cathode of the first semi-controlled valve is connected to the anode of the fourth valve unit, and the anode of the third semi-controlled valve is connected to the cathode of the third valve unit. The first fully controlled valve, the second fully controlled valve, and the seventh valve unit employ... Figure 9 The unidirectional fully controlled switch shown in (e) consists of IGBT modules connected in series.

[0184] In some implementations, if the maximum voltage value of each bridge arm circuit is 1.0 pu, then the maximum voltage values ​​of the first fully controlled valve, the first partially controlled valve, the second partially controlled valve, the third valve unit, the fifth valve unit, and the seventh valve unit are 0.1 pu, 0.6 pu, 0.4 pu, 0.6 pu, 0.6 pu, and 0.6 pu, respectively; and the maximum voltage values ​​of the second fully controlled valve, the third partially controlled valve, the fourth partially controlled valve, the fourth valve unit, the sixth valve unit, and the seventh valve unit are 0.1 pu, 0.6 pu, 0.4 pu, 0.6 pu, 0.6 pu, and 0.6 pu, respectively.

[0185] In some implementations, if the maximum voltage value of each bridge arm circuit is 1.0 pu, then the maximum voltage values ​​of the first fully controlled valve, the first partially controlled valve, the second partially controlled valve, the third valve unit, the fifth valve unit, and the seventh valve unit are 0.1 pu, 0.2 pu, 0.8 pu, 0.2 pu, 0.2 pu, and 0.6 pu, respectively; and the maximum voltage values ​​of the second fully controlled valve, the third partially controlled valve, the fourth partially controlled valve, the fourth valve unit, the sixth valve unit, and the seventh valve unit are 0.1 pu, 0.2 pu, 0.8 pu, 0.2 pu, 0.2 pu, and 0.6 pu, respectively.

[0186] Please see Figure 19 , Figure 19 This is a circuit diagram of another controllable shutdown hybrid grid commutator provided in an embodiment of this application. Figure 19 Circuit diagram and Figure 7 The corresponding topological structure. Figure 19 and Figure 17 The circuit diagrams are largely the same, the difference being that... Figure 19 The upper bridge arm circuit 1 connects the first semi-controlled valve, the second semi-controlled valve, and the first fully controlled valve in series. The other end of the upper bridge transfer circuit 3 is connected between the third and fourth semi-controlled valves of the lower bridge arm circuit 2. The lower bridge arm circuit connects the third semi-controlled valve, the fourth semi-controlled valve, and the second fully controlled valve in series. The other end of the lower bridge transfer circuit 4 is connected between the first and second semi-controlled valves of the upper bridge arm circuit 1.

[0187] The first semi-controlled valve, the third semi-controlled valve, the third valve unit, the fourth valve unit, the fifth valve unit, and the sixth valve unit all adopt the following... Figure 9 The unidirectional semi-controlled switch shown in (b) consists of thyristors connected in series. The cathode of the first semi-controlled valve is connected to the anode of the fourth valve unit, and the anode of the third semi-controlled valve is connected to the cathode of the third valve unit. The second and fourth semi-controlled valves employ... Figure 9 The bidirectional semi-controlled switch shown in (c) consists of thyristors connected in reverse parallel and then in series. The first fully controlled valve, the second fully controlled valve, and the seventh valve unit employ... Figure 9 The unidirectional fully controlled switch shown in (e) consists of IGBT modules connected in series. In some embodiments, the seventh valve unit may also be a bidirectional fully controlled switch.

[0188] Please see Figure 20 , Figure 20 This is a circuit diagram of another controllable shutdown hybrid grid commutator provided in an embodiment of this application. Figure 20 Circuit diagram and Figure 8 The corresponding topological structure. Figure 20 and Figure 17 The circuit diagrams are largely the same, the difference being that... Figure 20exist Figure 17 Based on this, the upper bridge arm circuit 1 connects the first fully controlled valve and the eighth valve unit in series, and a fifth semi-controlled valve is connected in parallel across the two ends of the series connection between the first fully controlled valve and the eighth valve unit. The eighth valve unit provides reverse withstand pressure for the first fully controlled valve, and the fifth semi-controlled valve protects the first fully controlled valve and allows it to continue operating in the event of failure. The lower bridge arm circuit 2 connects the second fully controlled valve and the ninth valve unit in series, and a sixth semi-controlled valve is connected in parallel across the two ends of the series connection between the second fully controlled valve and the ninth valve unit. The ninth valve unit provides reverse withstand pressure for the second fully controlled valve, and the sixth semi-controlled valve protects the second fully controlled valve and allows it to continue operating in the event of failure.

[0189] For example, the upper bridge arm circuit 1 of phase A includes a first fully controlled valve V44, an eighth valve unit V48, a first semi-controlled valve V45, a second semi-controlled valve V46, and a fifth semi-controlled valve V47; wherein, the first fully controlled valve V44 and the eighth valve unit V48 are connected in series and then in parallel with the fifth semi-controlled valve V47, and after being connected in parallel, they are connected in series with the first semi-controlled valve V45 and the second semi-controlled valve V46. The lower bridge arm circuit 2 of phase A includes a second fully controlled valve V14, a ninth valve unit V18, a third semi-controlled valve V15, a fourth semi-controlled valve V16, and a sixth semi-controlled valve V17; the second fully controlled valve V14 and the ninth valve unit V18 are connected in series and then in parallel with the sixth semi-controlled valve V17, and after being connected in parallel, they are connected in series with the third semi-controlled valve V15 and the fourth semi-controlled valve V16. One end of the first fully controlled valve V44 is connected to the anode bus P1, one end of the second semi-controlled valve V46 is connected to the lower bridge arm circuit 2 of phase A, one end of the second fully controlled valve V14 is connected to the cathode bus N1, and one end of the fourth semi-controlled valve V16 is connected to the upper bridge arm circuit 1 of phase A. The connection method and structure of the phase B bridge arm circuit and the phase C bridge arm circuit are similar to those of the phase A bridge arm circuit, and will not be described in detail here.

[0190] Figure 20 The first, second, third, fourth, fifth, and sixth semi-control valves, as well as the third, fourth, fifth, and sixth valve units shown, all employ the following... Figure 9 The unidirectional semi-controlled switch shown in (b) consists of thyristors connected in series. The cathode of the first semi-controlled valve unit is connected to the cathode of the third valve unit, and the anode of the third semi-controlled valve unit is connected to the anode of the fourth valve unit. The eighth and ninth valve units employ... Figure 9 The one-way uncontrolled switch shown in (a) consists of diodes connected in series. The cathode of the eighth valve unit is connected to the cathode of the fifth semi-controlled valve, and the anode of the ninth valve unit is connected to the anode of the sixth semi-controlled valve. The first fully controlled valve, the second fully controlled valve, and the seventh valve unit employ... Figure 9 The unidirectional fully controlled switch shown in (e) consists of IGBT modules connected in series.

[0191] Please see Figure 21 , Figure 21This is a circuit diagram of another controllable shutdown hybrid grid commutator provided in an embodiment of this application. Figure 21 and Figure 20 The circuit diagrams are largely the same, the difference being that... Figure 21 In the auxiliary circuit, the upper bridge transfer circuit 3 is connected to the lower bridge arm circuit 2, and the lower bridge transfer circuit 4 is connected to the upper bridge arm circuit 1. For example, the other end of the third valve unit of the upper bridge transfer circuit 3 is connected between the third and fourth semi-controlled valves of the lower bridge arm circuit 2, and the other end of the fourth valve unit of the lower bridge transfer circuit 4 is connected between the first and second semi-controlled valves of the upper bridge arm circuit 1. The cathode of the first semi-controlled valve is connected to the anode of the fourth valve unit, and the anode of the third semi-controlled valve is connected to the cathode of the third valve unit. Figure 21 The second semi-controlled valve, the fourth semi-controlled valve, the fifth valve unit, and the sixth valve unit adopt the following... Figure 9 The bidirectional semi-controlled switch shown in (c) is formed by first connecting thyristors in reverse parallel and then in series. This structure can achieve reverse rectification of DC current through the second, fourth, third, fourth, fifth, and sixth semi-controlled valves. Furthermore, this structure can form an anti-parallel circuit with the bridge arm circuit through the second, fourth, third, fourth, fifth, and sixth semi-controlled valves, thereby protecting the bridge arm circuit. Therefore, the withstand voltage level of the bridge arm circuit can be reduced, further lowering cost and losses.

[0192] Please see Figure 22 , Figure 22 This is a circuit diagram of another controllable shutdown hybrid grid commutator provided in the embodiments of this application. Figure 22 and Figure 17 They are basically the same, the difference lies in Figure 22 The first and second full control valves are both connected in parallel with the first surge arrester, and the seventh valve unit is connected in parallel with the second surge arrester. The surge arrester is used to absorb energy and provide the voltage required for commutation or phase switching when the full control valve is turned off.

[0193] Please continue reading. Figures 17 to 22 The first full-control valve, the second full-control valve, and the seventh valve unit can all be modular series switches. For example, such as... Figure 9 The module series switch shown in (k) consists of series-connected half-bridge sub-modules. During steady-state operation, the module series switch using the first fully controlled valve provides a relatively small commutation voltage, reducing the turn-off angle or firing angle, improving the power factor, and reducing reactive power consumption. During AC faults, the module series switch using the second fully controlled valve provides a larger commutation voltage, suppressing commutation failure or further reducing reactive power consumption during faults.

[0194] Secondly, this application provides a control method for a converter, used to control the converter provided in the above embodiments. Figure 23The diagram shown is a flowchart of the control method for a self-commutated converter provided in an embodiment of this application. Figure 23 As shown, the procedure includes steps S2310 to S2330. Wherein: Step S2310: If the operating state of the converter meets the transfer conditions, a switching control command is generated.

[0195] Step S2320: According to the switching control command, the target auxiliary circuit corresponding to the bridge arm to be turned off in the converter is turned on, so as to switch the current of the bridge arm to be turned off to the target auxiliary circuit.

[0196] Step S2330: When the bridge arm to be turned off is restored to the off state, a turn-off command is generated. According to the turn-off command, the target auxiliary circuit is controlled to output a commutation voltage to the bridge arm to be turned on, so as to realize the commutation operation from the bridge arm to be turned off to the bridge arm to be turned on.

[0197] The transfer condition indicates the conditions under which a self-commutated converter needs to perform self-commutation operation. The switching control command is a command that controls the various circuits of the self-commutated converter to switch the current of the bridge arm to be turned off during the self-commutation operation to the auxiliary circuit of the self-commutated converter.

[0198] Commutation means that current is transferred from one phase arm to another. Taking the transfer of current from the upper arm of phase A to the upper arm of phase B as an example, during commutation, the upper arm of phase B needs to be turned on and the upper arm of phase A turned off, so that the current in the upper arm of phase A flows to the upper arm of phase B. The commutation operation is completed after the current is transferred to the upper arm of phase B. At this time, the upper arm of phase A is the arm to be turned off, and the upper arm of phase B is the arm to be turned on.

[0199] The converter in this embodiment can, when a commutation failure or other transfer condition is triggered, switch the current of the arm to be turned off to the target auxiliary circuit corresponding to the arm to be turned off according to a switching control command. When the arm to be turned off is restored, the target auxiliary circuit outputs a commutation voltage to the arm to be turned on based on the turn-off command, causing the current to transfer from the arm to be turned off to the arm to be turned on, thereby realizing the commutation operation from the arm to be turned off to the arm to be turned on, effectively solving the problem of commutation failure.

[0200] In this embodiment, when the converter meets the switching conditions, the current of the arm to be turned off is transferred to the target auxiliary circuit corresponding to the arm to be turned off, thereby realizing self-commutation operation and avoiding commutation failure. Installing the self-commutated converter of this embodiment in a high-voltage direct current transmission system can improve system reliability.

[0201] In some embodiments, the switching conditions in step S2310 include at least one of the following: the self-commutated converter switches phase when the cutoff angle reference value is less than the minimum cutoff angle in the inverter state; the self-commutated converter switches phase when the firing angle reference value is less than the minimum firing angle in the rectification state; and the self-commutated converter switches phase when there is a commutation fault in the inverter state.

[0202] Before determining whether a self-commutated converter meets the switching conditions, it is necessary to first determine the converter's operating status. For example, the operating status of a self-commutated converter can be determined by real-time monitoring of its operating status parameters. These operating status parameters can include AC voltage, DC current, etc.

[0203] When the converter is determined to be in inverter mode, each bridge arm circuit in the converter main circuit operates in inverter mode according to the inverter mode control command. When the converter is determined to be in rectification mode, each bridge arm circuit in the converter main circuit operates in rectification mode according to the rectification mode control command.

[0204] by Figure 1 Taking the self-commutated converter shown as an example, in inverter mode, the half-controlled valves V41 (upper arm circuit of phase A), V11 (lower arm circuit of phase A), V61 (upper arm circuit of phase B), V31 (lower arm circuit of phase B), V21 (upper arm circuit of phase C), and V51 (lower arm circuit of phase C) can be controlled to operate in inverter mode according to the six-pulse inverter operating mode. In rectification mode, the half-controlled valves V41 (upper arm circuit of phase A), V11 (lower arm circuit of phase A), V61 (upper arm circuit of phase B), V31 (lower arm circuit of phase B), V21 (upper arm circuit of phase C), and V51 (lower arm circuit of phase C) can be controlled to operate in rectification mode according to the six-pulse rectifier operating mode.

[0205] The turn-off angle, in inverter mode, is the time interval from when the thyristor current naturally drops to zero to when it withstands forward voltage; it is expressed as an electrical angle. The turn-off angle reference value is set according to the requirements of the transmission system. The minimum turn-off angle is the minimum turn-off angle at which a self-commutated converter can operate safely relying solely on grid voltage, for example, 7°. If the turn-off angle reference value is less than the minimum turn-off angle, the self-commutated converter in inverter mode cannot reach the set turn-off angle when relying solely on grid voltage for commutation, leading to abnormal commutation and affecting system stability. Self-commutated converters possess self-commutation capability, enabling them to complete commutation operations independently. In some implementations, the minimum turn-off angle can range from -50° to 30°.

[0206] The firing angle, in rectification mode, is the time interval from the natural commutation point of the AC power supply to the application of the firing pulse to the thyristor, expressed as an electrical angle. The firing angle reference value is set according to the requirements of the power transmission system. The minimum firing angle is the smallest firing angle at which a self-commutated converter can operate safely relying solely on the grid voltage, for example, 5°. If the firing angle reference value is less than the minimum firing angle, the self-commutated converter in rectification mode cannot reach the set firing angle when relying solely on the grid voltage for commutation, leading to abnormal commutation and affecting system stability. Self-commutated converters possess self-commutation capability, enabling them to complete commutation operations independently. In some implementations, the minimum firing angle can range from -50° to 5°.

[0207] Commutation faults can be identified based on fault information. This fault information indicates the failure of natural commutation of the arm to be turned off. Commutation faults can be caused by AC system faults connected to the self-commutating converter or DC system faults connected to the self-commutating converter. AC system faults can be identified by an increase in the zero-sequence component of AC voltage, sudden changes in AC voltage, a drop in AC voltage amplitude, an increase in AC voltage harmonics, and an increase in DC current. DC system faults can be identified by a drop in DC voltage and an increase in DC current. Commutation faults can also be identified based on the closing time of the half-controlled valve of the arm to be turned off, the AC current on the grid side or the valve side, and the AC voltage. For example, if the half-controlled valve of the arm to be turned off has not closed by the time it begins to bear positive pressure under normal AC voltage, a commutation fault is identified.

[0208] In some embodiments, the target auxiliary circuit includes a target transfer circuit, a target isolation circuit, and a full-bridge circuit corresponding to the bridge arm to be turned off; turning on the target auxiliary circuit corresponding to the bridge arm to be turned off in the converter according to the switching control command includes: turning on the target transfer circuit and the target isolation circuit according to the switching control command, and controlling the full-bridge circuit to generate a commutation voltage so that the current of the bridge arm to be turned off is switched to the target auxiliary circuit.

[0209] by Figure 1 Taking the self-commutated converter shown as an example, the bridge arm to be turned off is either the upper bridge arm circuit or the lower bridge arm circuit. Each bridge arm circuit has a corresponding transfer circuit. The target transfer circuit represents the transfer circuit connected to the bridge arm to be turned off, and the target isolation circuit represents the isolation circuit connected to the target transfer circuit. The commutation voltage is generated by the full-bridge circuit and is used to control the current of the bridge arm to be turned off to switch to the voltage of the target auxiliary circuit.

[0210] For example, still using Figure 1Taking a self-commutated converter as an example, when the self-commutated converter is in inverter mode and the minimum turn-off angle is 7°, when the current commutates from the upper bridge arm of phase A to the upper bridge arm of phase B, if the reference value of the turn-off angle is less than the minimum turn-off angle, the half-controlled valve V43 of the upper bridge transfer circuit of phase A and the half-controlled valve V71 of the upper bridge isolation circuit of the auxiliary circuit are controlled to conduct according to the switching control command. Based on the switching control command, the full-controlled valve V81 of the full bridge circuit is controlled to provide negative pressure, so that the current of the upper bridge arm circuit of phase A is transferred to the upper bridge transfer circuit of phase A, the upper bridge isolation circuit and the full bridge circuit of the auxiliary circuit. When it is detected that the half-controlled valve V41 of the upper bridge arm circuit 1 of phase A of the main circuit is restored to turn off, a turn-off command is generated. The self-commutated converter responds to the turn-off command and controls the full bridge circuit of the auxiliary circuit to provide positive pressure, so that the current is transferred from the upper bridge arm circuit of phase A to the upper bridge arm circuit of phase B. When current commutates from the lower bridge arm circuit of phase A to the lower bridge arm circuit of phase B, if the cut-off angle reference value is less than the minimum cut-off angle, the half-controlled valve V13 of the lower bridge transfer circuit of phase A in the auxiliary circuit and the half-controlled valve V72 of the lower bridge isolation circuit 6 are controlled to conduct according to the switching control command, and the full-controlled valve V81 of the full bridge circuit is controlled to provide negative pressure, so that the current of the lower bridge arm circuit of phase A is transferred to the lower bridge transfer circuit of phase A, the lower bridge isolation circuit and the full bridge circuit of the auxiliary circuit; when it is detected that the half-controlled valve V11 of the lower bridge arm circuit of phase A in the main circuit is restored to cut-off, a cut-off command is generated, the self-commutating converter responds to the cut-off command, and the full bridge circuit of the auxiliary circuit is controlled to provide positive pressure, so that the current is transferred from the lower bridge arm circuit of phase A to the lower bridge arm circuit of phase B.

[0211] In the full-bridge circuit including Figure 10A In the case of the full-bridge submodule shown, it can be controlled Figure 10A The full-bridge submodule uses IGBT modules M2 and M3 to conduct and M1 and M4 to turn off to provide negative voltage to the full-bridge circuit. The full-bridge circuit includes... Figure 10B In the case of the full-bridge submodule shown, it can be controlled Figure 10B The IGBT modules M5 and M6 of the full-bridge submodule are turned on to provide negative voltage to the full-bridge circuit. The full-bridge circuit includes... Figure 10A In the case of the full-bridge submodule shown, it can be controlled Figure 10A The IGBT modules M2 and M3 of the full-bridge submodule are turned off, while M1 and M4 are turned on, to provide positive voltage to the full-bridge circuit. This is achieved by turning off the IGBT modules M2 and M3 and turning on M1 and M4. The full-bridge circuit includes... Figure 10B In the case of the full-bridge submodule shown, it can be controlled Figure 10B The IGBT modules M5 and M6 of the full-bridge submodule are turned off to provide positive voltage to the full-bridge circuit.

[0212] When the self-commutated converter is in rectification mode and the minimum firing angle is 5°, when the current commutates from the upper bridge arm circuit of phase A to the upper bridge arm circuit of phase B, if the firing angle reference value is less than the minimum firing angle, the half-controlled valve V43 of the upper bridge transfer circuit of phase A and the half-controlled valve V71 of the upper bridge isolation circuit of the auxiliary circuit are controlled to conduct according to the switching control command, and the full-controlled valve V81 of the full bridge circuit is controlled to provide negative pressure, so that the current of the upper bridge arm circuit of phase A is transferred to the upper bridge transfer circuit of phase A, the upper bridge isolation circuit and the full bridge circuit of the auxiliary circuit; when it is detected that the half-controlled valve V41 of the upper bridge arm circuit 1 of phase A of the main circuit is turned off, a turn-off command is generated, the self-commutated converter responds to the turn-off command, and controls the full bridge circuit of the auxiliary circuit to provide positive pressure, so that the current is transferred from the upper bridge arm circuit of phase A to the upper bridge arm circuit of phase B. When current commutates from the lower bridge arm circuit of phase A to the lower bridge arm circuit of phase B, if the reference value of the firing angle is less than the minimum firing angle, the half-controlled valve V13 of the lower bridge transfer circuit of phase A and the half-controlled valve V72 of the lower bridge isolation circuit of the auxiliary circuit are controlled to conduct according to the switching control command, and the full-controlled valve V81 of the full bridge circuit is controlled to provide negative pressure, so that the current of the lower bridge arm circuit of phase A is transferred to the lower bridge transfer circuit of phase A, the lower bridge isolation circuit and the full bridge circuit of the auxiliary circuit; when it is detected that the half-controlled valve V11 of the lower bridge arm circuit of phase A of the main circuit is restored to shut off, a shutdown command is generated, the self-commutating converter responds to the shutdown command, and controls the full bridge circuit of the auxiliary circuit to provide positive pressure, so that the current is transferred from the lower bridge arm circuit of phase A to the lower bridge arm circuit of phase B.

[0213] In this embodiment, when the turn-off angle reference value is less than the minimum turn-off angle, or the firing angle reference value is less than the minimum firing angle, commutation operation can be achieved by the auxiliary circuit generating a commutation voltage, thereby reducing the turn-off angle reference value or the firing angle reference value and reducing the reactive power consumed by the system. During steady-state operation, the commutation voltage required by the self-commutated converter is lower than the commutation voltage required for single-phase or two-phase ground faults in the AC system. Therefore, the module series switches of the full-bridge circuit can be configured only according to the steady-state required commutation voltage. During AC system faults, the module series switches and surge arresters can jointly provide the commutation voltage, thereby reducing the cost of the full-bridge circuit.

[0214] In some embodiments, the target auxiliary circuit includes a target transfer circuit, a target isolation circuit, and a full-bridge circuit corresponding to the bridge arm to be turned off; according to the switching control command, the target auxiliary circuit corresponding to the bridge arm to be turned off in the controllable turn-off hybrid grid phase-change converter is turned on, including: according to the switching control command, the target transfer circuit, the target isolation circuit, and the full-bridge circuit are turned on, and the full control valve is controlled to generate a commutation voltage so that the current of the bridge arm to be turned off is switched to the target auxiliary circuit.

[0215] by Figure 5Taking the controllable shutdown hybrid grid-commutated converter as an example, the bridge arm to be shut down is either the upper or lower bridge arm circuit. Each bridge arm circuit has a corresponding transfer circuit. The target transfer circuit represents the transfer circuit connected to the bridge arm to be shut down, and the target isolation circuit represents the isolation circuit connected to the target transfer circuit. The commutation voltage is generated by the full-bridge circuit and is used to control the current of the bridge arm to be shut down to switch to the voltage of the target auxiliary circuit.

[0216] For example, still using Figure 5 Taking a controllable shutdown hybrid grid phase-commutation converter as an example, when the controllable shutdown hybrid grid phase-commutation converter is in the inverter state, if a fault occurs in the AC system and the natural commutation fails, the third valve unit V43 of the A-phase upper bridge transfer circuit, the fifth valve unit V71 of the upper bridge isolation circuit, and the seventh valve unit V81 of the full bridge circuit in the auxiliary circuit are turned on according to the switching control command, and the first full control valve V44 of the A-phase upper bridge arm is turned off, so that the current of the A-phase upper bridge arm circuit is transferred to the A-phase upper bridge transfer circuit, the upper bridge isolation circuit, and the full bridge circuit in the auxiliary circuit. When it is detected that the first half control valve V45 of the A-phase upper bridge arm circuit 1 of the main circuit is restored to shutdown, a shutdown command is generated. The controllable shutdown hybrid grid phase-commutation converter responds to the shutdown command and controls the full bridge circuit of the auxiliary circuit to provide positive voltage, so that the current is transferred from the A-phase upper bridge arm circuit to the B-phase upper bridge arm circuit. When current commutates from the lower bridge arm circuit of phase A to the lower bridge arm circuit of phase B, if a fault occurs in the AC system causing the natural commutation to fail, the fourth valve unit V13 of the lower bridge transfer circuit of phase A, the sixth valve unit V72 of the lower bridge isolation circuit 6, and the seventh valve unit V81 of the full bridge circuit in the auxiliary circuit are turned on according to the switching control command, and the second full control valve V14 of the lower bridge arm of phase A is turned off, so that the current of the lower bridge arm circuit of phase A is transferred to the lower bridge transfer circuit of phase A, the lower bridge isolation circuit, and the full bridge circuit in the auxiliary circuit. When it is detected that the third half control valve V15 of the lower bridge arm circuit of phase A in the main circuit is turned off again, a shutdown command is generated, and the hybrid grid commutation converter responds to the shutdown command and controls the full bridge circuit of the auxiliary circuit to provide positive voltage, so that the current is transferred from the lower bridge arm circuit of phase A to the lower bridge arm circuit of phase B.

[0217] When the controllable shut-off hybrid grid phase-commutation converter is in rectification mode and the minimum firing angle is 5°, when the current commutates from the upper bridge arm circuit of phase A to the upper bridge arm circuit of phase B, if the firing angle reference value is less than the minimum firing angle, the third valve unit V43 of the upper bridge transfer circuit of phase A, the fifth valve unit V71 of the upper bridge isolation circuit and the seventh valve unit V81 of the full bridge circuit of the auxiliary circuit are turned on according to the switching control command, and the first full control valve V44 of the upper bridge arm of phase A is turned off, so that the current of the upper bridge arm circuit of phase A is transferred to the upper bridge transfer circuit of phase A, the upper bridge isolation circuit and the full bridge circuit of the auxiliary circuit; when it is detected that the first half control valve V45 of the upper bridge arm circuit 1 of phase A in the main circuit is restored to shut off, a shutdown command is generated, and the controllable shut-off hybrid grid phase-commutation converter responds to the shutdown command, controlling the full bridge circuit of the auxiliary circuit to provide positive voltage, so that the current is transferred from the upper bridge arm circuit of phase A to the upper bridge arm circuit of phase B. When current commutates from the lower bridge arm circuit of phase A to the lower bridge arm circuit of phase B, if the reference value of the firing angle is less than the minimum firing angle, the fourth valve unit V13 of the lower bridge transfer circuit of phase A, the sixth valve unit V72 of the lower bridge isolation circuit, and the seventh valve unit V81 of the full bridge circuit in the auxiliary circuit are turned on according to the switching control command, and the second full control valve V14 of the lower bridge arm of phase A is turned off, so that the current of the lower bridge arm circuit of phase A is transferred to the lower bridge transfer circuit of phase A, the lower bridge isolation circuit, and the full bridge circuit in the auxiliary circuit. When it is detected that the third half control valve V15 of the lower bridge arm circuit of phase A in the main circuit is restored to closed, a shutdown command is generated, and the hybrid grid phase-commutation converter responds to the shutdown command and controls the full bridge circuit of the auxiliary circuit to provide positive voltage, so that the current is transferred from the lower bridge arm circuit of phase A to the lower bridge arm circuit of phase B.

[0218] In some embodiments, a shutdown command is generated when the reverse recovery time of a single valve in the bridge arm to be shut down is greater than or equal to the reverse recovery time of the thyristor in the single valve.

[0219] Whether the bridge arm to be turned off has recovered can be determined by judging the reverse recovery time of the single valve in the bridge arm to be turned off. When the reverse recovery time of the single valve in the bridge arm to be turned off is greater than or equal to the reverse recovery time of the thyristor included in the single valve, a turn-off command is generated. The reverse recovery time of the thyristor can be from 200μs to 800μs, and the reverse recovery time of the single valve can be from 200μs to 1.5ms.

[0220] In some embodiments, the converter control method further includes: during a non-commutation period of the converter, controlling the switching on of the isolation circuit and / or the transfer circuit corresponding to the non-switching bridge arm of the converter to charge or discharge the fully controlled submodule of a single valve in the full-bridge circuit of the self-commutated converter.

[0221] During non-commutation periods, the fully controlled submodules in the single valve of the full-bridge circuit of the self-commutated converter can be charged or discharged. For example, the upper bridge isolation circuit and the lower bridge isolation circuit can be controlled to be turned on, or the upper bridge transfer circuit of the non-conducting bridge arm can be turned on, or the lower bridge isolation circuit and the lower bridge transfer circuit of the non-conducting bridge arm can be turned on.

[0222] In some embodiments, the converter control method further includes: charging and discharging different fully controlled sub-modules of a single valve in the full-bridge circuit through DC-side control to maintain the voltage balance of the full-bridge circuit.

[0223] For example, in the full-bridge circuit's fully controlled valve, some fully controlled submodules with larger capacitor voltage values ​​are selected as negative voltage, while other fully controlled submodules are in a positive voltage or bypass state. In this case, the fully controlled submodules with larger capacitor voltage values ​​in the full-bridge circuit's fully controlled valve discharge, thereby reducing the capacitor voltage value of the fully controlled submodule. Alternatively, some fully controlled submodules with smaller capacitor voltage values ​​are selected as positive voltage, while others are in a bypass state. In this case, the fully controlled submodules with smaller voltage values ​​in the full-bridge circuit's fully controlled valve are charged, thereby increasing the capacitor voltage value of the fully controlled submodule.

[0224] In some embodiments, when the converter is operating normally, the converter control method further includes: generating a shutdown command in advance when the capacitor voltage of the full-bridge circuit of the converter is less than a first preset value; and delaying the generation of a shutdown command when the capacitor voltage of the full-bridge circuit of the converter is greater than or equal to a second preset value, so as to maintain the stability of the capacitor voltage of each sub-module of the full-bridge circuit.

[0225] For example, under normal operation of the self-commutated converter, if the capacitor voltage of the full-bridge circuit of the self-commutated converter is less than a first preset value (i.e., the capacitor voltage in the fully controlled submodule is lower than the rated value and exceeds a first threshold), and the half-controlled valve of the main circuit's arm to be turned off resumes its shutdown state, a circuit shutdown command is generated in advance. The first threshold value ranges from 0.01 to 0.6 times the rated capacitor voltage. If the capacitor voltage of the full-bridge circuit of the self-commutated converter is greater than or equal to a second preset value (i.e., the capacitor voltage in the fully controlled submodule is greater than or equal to the rated value and exceeds the second threshold), and the half-controlled valve of the main circuit's arm to be turned off resumes its shutdown state, the generation of the circuit shutdown command is delayed. The second threshold value ranges from 0.01 to 0.6 times the rated capacitor voltage.

[0226] In some embodiments, the converter employs a grid control strategy.

[0227] The grid control strategy controls the converter to actively provide voltage, frequency, and inertia support to the connected AC system, rather than passively following the grid. This allows the voltage amplitude and phase output by the converter to be determined by its own control logic, enabling it to independently support the grid and improve the stability of new energy grid connection.

[0228] In some embodiments, where the converter also includes an energy storage circuit, the converter can also interact with the AC system by controlling the charging and discharging of the energy storage circuit.

[0229] In some embodiments, the converter control method further includes: in the event of a fault in the auxiliary circuit of the converter, disconnecting the first disconnecting switch or the first disconnecting switch between the fifth valve unit of the upper bridge isolation circuit in the converter and the bus, and the second disconnecting switch or the second disconnecting switch between the sixth valve unit of the lower bridge isolation circuit in the converter and the bus.

[0230] The isolation circuit in this embodiment includes an upper-bridge isolation circuit and a lower-bridge isolation circuit. The fifth valve unit of the upper-bridge isolation circuit is connected to the anode bus via a first disconnect switch or a first disconnector, and the sixth valve unit of the lower-bridge isolation circuit is connected to the cathode bus via a second disconnect switch or a second disconnector. In the event of a fault in the auxiliary circuit of the converter, the first disconnect switch or the first disconnector, as well as the second disconnect switch or the second disconnector, are controlled to disconnect to ensure the stability of the converter. It is understood that a fault in the auxiliary circuit indicates that the auxiliary circuit cannot operate normally; this could be a fault in a semiconductor device within the auxiliary circuit, or a fault in a module composed of semiconductor devices within the auxiliary circuit.

[0231] Based on the same inventive concept, this application also provides a converter control device for implementing the converter control method described above. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations in one or more converter control device embodiments provided below can be found in the limitations of the converter control method described above, and will not be repeated here.

[0232] Thirdly, such as Figure 24 As shown, a control device for a converter is provided for controlling the converter provided in the above embodiments. The device includes: The instruction generation module 2410 is used to generate switching control instructions when the converter meets the switching conditions.

[0233] The switching module 2420 is used to turn on the target auxiliary circuit corresponding to the bridge arm to be turned off in the converter according to the switching control command, so as to switch the current of the bridge arm to be turned off to the target auxiliary circuit.

[0234] The commutation module 2430 is used to generate a turn-off command when the bridge arm to be turned off is restored to turn-off, and control the target auxiliary circuit to output a commutation voltage to the bridge arm to be turned on according to the turn-off command, so as to realize the commutation operation from the bridge arm to be turned off to the bridge arm to be turned on.

[0235] The various modules in the control device of the aforementioned converter can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0236] Fourthly, a high-voltage direct current (HVDC) transmission system is provided, wherein at least one converter in the HVDC transmission system is provided as a converter in the above embodiments.

[0237] In some embodiments, a high-voltage direct current transmission system includes a two-terminal direct current transmission system or a multi-terminal direct current transmission system.

[0238] A two-terminal DC transmission system refers to a high-voltage DC transmission system with only two converter stations or converters. One station performs the rectification operation to convert AC power to DC power, and the other station performs the inversion operation to convert DC power to AC power. The two converter stations are connected by a DC transmission line.

[0239] A multi-terminal DC transmission system refers to a high-voltage DC transmission system with multiple converter stations or converters. Some converter stations perform rectification operations, while others perform inverter operations. These converter stations are connected by DC transmission lines to form a complex network.

[0240] In some embodiments, the high-voltage direct current transmission system includes a monopolar direct current transmission system, a bipolar direct current transmission system, or a back-to-back direct current system.

[0241] A unipolar DC transmission system refers to a system with only one DC transmission line and one grounding electrode. Current is transmitted through the DC line and returns through the grounding electrode, forming a complete loop. A bipolar DC transmission system refers to a system with two DC transmission lines (positive and negative) and one grounding electrode. Current is transmitted through both the positive and negative lines, forming a complete loop. A back-to-back DC system refers to a system where two converters (one rectifier and one inverter) are directly connected together in a converter station, without any DC transmission line in between. Back-to-back DC systems are mainly used to connect two asynchronous AC power grids.

[0242] This application does not limit the form of the DC transmission system. By configuring a self-commutated converter as described in the above embodiments in the DC transmission system, the commutation failure problem can be solved at low cost, reducing the reactive power consumed by the HVDC transmission system during faults or in steady state, and improving the reliability of the HVDC transmission system.

[0243] Figure 25 This is a schematic diagram of a single pole in a high-voltage direct current (HVDC) transmission system. Figure 25As shown, the high-voltage direct current (HVDC) transmission system is a bipolar HVDC transmission system. Each bipolar system includes a first AC system 13 and a second AC system 19. The first AC system 13 is connected to the first grid-commutated converter 9 via a first converter transformer 11 and to the second grid-commutated converter 10 via a second converter transformer 12. The second AC system 19 is connected to the first self-commutated converter 15 via a third converter transformer 17 and to the second self-commutated converter 16 via a fourth converter transformer 18. A DC line 14 is provided between the first grid-commutated converter 9 and the first self-commutated converter 15. The second grid-commutated converter 10 and the second self-commutated converter 16 are grounded.

[0244] Figure 26 This is a schematic diagram of another single pole in a high-voltage direct current transmission system. (See diagram below.) Figure 26 As shown, the high-voltage direct current (HVDC) transmission system is a bipolar HVDC transmission system. Each bipolar system includes a first AC system 13 and a second AC system 19. The first AC system 13 is connected to the first grid phase-commutator 9 via a first converter transformer 11 and to the second grid phase-commutator 10 via a second converter transformer 12. The second AC system 19 is connected to the first controllable shutdown hybrid grid phase-commutator 25 via a third converter transformer 17 and to the second controllable shutdown hybrid grid phase-commutator 26 via a fourth converter transformer 18. A DC line 14 is provided between the first grid phase-commutator 9 and the first controllable shutdown hybrid grid phase-commutator 25. The second grid phase-commutator 10 and the second controllable shutdown hybrid grid phase-commutator 26 are grounded.

[0245] like Figure 25 or Figure 26 As shown, during power transmission, the AC power from the first AC system 13, after passing through the first converter transformer 11 and the second converter transformer 12, is rectified into DC power by the first grid-commutated converter 9 and the second grid-commutated converter 10. This DC power is then transmitted through the DC line 14 to the first self-commutated converter 15 or the first controllable shutdown hybrid grid-commutated converter 25, the second self-commutated converter 16 or the second controllable shutdown hybrid grid-commutated converter 26, and inverted back into AC power. After passing through the third converter transformer 17 and the fourth converter transformer 18, this AC power is transmitted to the second AC system 19, thus realizing the transmission of DC power. Figure 25 In the structure, the first self-commutated converter 15 and the second self-commutated converter 16 are the self-commutated converters provided in the above embodiments of this application; Figure 26 In the structure, the first controllable shutdown hybrid grid phase-commutation converter 25 and the second controllable shutdown hybrid grid phase-commutation converter 26 are controllable shutdown hybrid grid phase-commutation converters provided in the above embodiments of this application, which have the ability to solve the commutation failure problem and ensure the reliability of DC power transmission.

[0246] Please continue reading. Figures 27A to 27C . Figure 27A Taking the ultra-high voltage direct current transmission system with the topology shown as an example, Figure 27A These are the test waveforms of the converter provided in this application embodiment during a phase A ground fault in an AC system. Figure 27A As can be seen, the fault time was 100ms. During the fault, the valve side current switched normally without any commutation failure. The DC voltage and DC current remained at a certain level, ensuring that some DC power continued to be transmitted.

[0247] Figure 27B These are the test waveforms of the converter provided in this application embodiment during short-circuit faults in phase A and phase B of the AC system. Figure 27B As can be seen, the fault time was 100ms. During the fault, the valve side current switched normally without any commutation failure. The DC voltage and DC current remained at a certain level, ensuring that some DC power continued to be transmitted.

[0248] Figure 27C These are the test waveforms of the converter provided in this application embodiment during a three-phase short-circuit fault in an AC system, from... Figure 27C As can be seen, the fault time is 100ms. During the fault period, the valve-side current commutates normally without any commutation failure. This application embodiment uses... Figure 17 Taking the converter with the topology shown as an example, similar test waveforms can be obtained for other topologies, which will not be elaborated here.

[0249] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0250] The present application provides a detailed description of a converter and its control method, control device, and high-voltage direct current transmission system. Specific examples have been used to illustrate the principles and implementation methods of the present application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of the present application. At the same time, those skilled in the art will recognize that there will be changes in the specific implementation methods and application scope based on the ideas of the present application. Therefore, the content of this specification should not be construed as a limitation of the present application.

Claims

1. A converter, characterized in that, include: The main circuit includes at least one phase bridge arm circuit, the bridge arm circuit including an upper bridge arm circuit and a lower bridge arm circuit connected in sequence, one end of the upper bridge arm circuit being connected to the anode bus, and one end of the lower bridge arm circuit being connected to the cathode bus. An auxiliary circuit, comprising an upper bridge isolation circuit, a full bridge circuit, and a lower bridge isolation circuit connected in sequence, wherein one end of the upper bridge isolation circuit is connected to the anode bus, and one end of the lower bridge isolation circuit is connected to the cathode bus; The auxiliary circuit further includes at least one phase transfer circuit, which includes an upper bridge transfer circuit and a lower bridge transfer circuit. One end of the upper bridge transfer circuit is connected between the full bridge circuit and the lower bridge isolation circuit, and the other end of the upper bridge transfer circuit is connected to the upper bridge arm circuit or the lower bridge arm circuit. One end of the lower bridge transfer circuit is connected between the upper bridge isolation circuit and the full bridge circuit, and the other end of the lower bridge transfer circuit is connected to the lower bridge arm circuit or the upper bridge arm circuit.

2. The converter according to claim 1, characterized in that, The upper bridge arm circuit includes a first valve unit, and the lower bridge arm circuit includes a second valve unit. One end of the first valve unit is connected to the anode bus, and the other end of the first valve unit is connected to one end of the second valve unit. The other end of the second valve unit is connected to the cathode bus.

3. The converter according to claim 2, characterized in that, The first valve unit includes at least one single valve, and the second valve unit includes at least one single valve.

4. The converter according to claim 3, characterized in that, The single valve of the first valve unit and / or the second valve unit is a semi-controlled valve and / or a fully controlled valve.

5. The converter according to claim 3, characterized in that, When the first valve unit or the second valve unit includes two single valves, the pressure resistance ratio of the two single valves ranges from 0.1 to 10.

6. The converter according to claim 2, characterized in that, The upper bridge transfer circuit includes a third valve unit, and the lower bridge transfer circuit includes a fourth valve unit; the single valve of the third valve unit and / or the fourth valve unit includes at least one of the following: a semi-controlled valve, and a non-controlled valve.

7. The converter according to claim 3, characterized in that, In the case where the first valve unit includes a single valve, the connection point between the upper bridge transfer circuit and the upper bridge arm circuit is located at the other end of the first valve unit; In the case where the second valve unit includes a single valve, the connection point between the lower bridge transfer circuit and the lower bridge arm circuit is located at one end of the second valve unit.

8. The converter according to claim 3, characterized in that, When the first valve unit includes two single valves, the connection point between the upper bridge transfer circuit and the upper bridge arm circuit is located between the two single valves of the first valve unit. In the case where the second valve unit comprises two single valves, the connection point between the lower bridge transfer circuit and the lower bridge arm circuit is located between the two single valves of the second valve unit.

9. The converter according to claim 3, characterized in that, When the first valve unit includes two single valves, the connection point between the lower bridge transfer circuit and the upper bridge arm circuit is located between the two single valves of the first valve unit. In the case where the second valve unit comprises two single valves, the connection point between the upper bridge transfer circuit and the lower bridge arm circuit is located between the two single valves of the second valve unit.

10. The converter according to claim 6, characterized in that, The first valve unit includes a first fully controlled valve, a first partially controlled valve, and a second partially controlled valve connected in series, and the lower bridge arm circuit includes a second fully controlled valve, a third partially controlled valve, and a fourth partially controlled valve connected in series; The upper bridge transfer circuit is connected between the first fully controlled valve and the first partially controlled valve, and the lower bridge transfer circuit is connected between the second fully controlled valve and the third partially controlled valve; or, the upper bridge transfer circuit is connected between the first partially controlled valve and the second partially controlled valve, and the lower bridge transfer circuit is connected between the third partially controlled valve and the fourth partially controlled valve; or, the upper bridge transfer circuit is connected between the third partially controlled valve and the fourth partially controlled valve, and the lower bridge transfer circuit is connected between the first partially controlled valve and the second partially controlled valve; or, the upper bridge transfer circuit is connected between the second fully controlled valve and the third partially controlled valve, and the lower bridge transfer circuit is connected between the first fully controlled valve and the first partially controlled valve.

11. The converter according to claim 10, characterized in that, The upper arm circuit also includes a fifth semi-control valve, and the first full control valve is connected in parallel with the fifth semi-control valve. The lower arm circuit also includes a sixth semi-control valve, and the second full control valve is connected in parallel with the sixth semi-control valve.

12. The converter according to claim 11, characterized in that, The upper bridge arm circuit also includes an eighth valve unit, wherein the first fully controlled valve is connected in series with the eighth valve unit and then connected in parallel with the fifth semi-controlled valve. The lower bridge arm circuit also includes a ninth valve unit, and the second fully controlled valve is connected in series with the ninth valve unit and then connected in parallel with the sixth semi-controlled valve. The eighth valve unit includes an uncontrolled valve and / or a semi-controlled valve; the ninth valve unit includes an uncontrolled valve and / or a semi-controlled valve.

13. The converter according to claim 10, characterized in that, The pressure resistance ratio of the first and second semi-controlled valves ranges from 0.1 to 10; the pressure resistance ratio of the third and fourth semi-controlled valves ranges from 0.1 to 10.

14. The converter according to claim 6, characterized in that, The upper bridge isolation circuit includes a fifth valve unit, and the lower bridge isolation circuit includes a sixth valve unit; the single valve of the fifth valve unit and / or the sixth valve unit includes at least one of the following: a fully controlled valve, a partially controlled valve, and a non-controlled valve.

15. The converter according to claim 14, characterized in that, The upper bridge isolation circuit further includes a first disconnect switch or a first disconnect switch, and the lower bridge isolation circuit further includes a second disconnect switch or a second disconnect switch; the fifth valve unit is connected to the anode bus via the first disconnect switch or the first disconnect switch, and the sixth valve unit is connected to the cathode bus via the second disconnect switch or the second disconnect switch.

16. The converter according to claim 14, characterized in that, The upper bridge isolation circuit further includes a third disconnect switch or a third disconnector, and the lower bridge isolation circuit further includes a fourth disconnect switch or a fourth disconnector; the fifth valve unit of the upper bridge isolation circuit is connected in parallel with the third disconnect switch or the third disconnector, and the sixth valve unit of the lower bridge isolation circuit is connected in parallel with the fourth disconnect switch or the fourth disconnector.

17. The converter according to any one of claims 4, 6, 10, 11, 12 or 14, characterized in that, The semi-controlled valve includes a one-way semi-controlled switch or a two-way semi-controlled switch; wherein... The unidirectional semi-controlled switch includes several semi-controlled devices connected in series. The bidirectional semi-controlled switch includes a plurality of first semi-controlled units connected in series, each first semi-controlled unit including a plurality of anti-parallel semi-controlled devices; or, the bidirectional semi-controlled switch includes a plurality of second semi-controlled units connected in anti-parallel, each second semi-controlled unit including a plurality of series semi-controlled devices.

18. The converter according to claim 6, 12 or 14, characterized in that, The uncontrolled valve comprises several uncontrolled devices connected in series.

19. The converter according to claim 14, characterized in that, The converter further includes a first surge arrester, which is connected in parallel with at least one of the following single valves: The single valve in the first valve unit, the single valve in the second valve unit, the single valve in the third valve unit, the single valve in the fourth valve unit, the single valve in the fifth valve unit, and the single valve in the sixth valve unit.

20. The converter according to claim 1, characterized in that, The full-bridge circuit includes a seventh valve unit, which includes a fully controllable valve.

21. The converter according to claim 20, characterized in that, The full-bridge circuit also includes a resistor unit or an inductor unit, which is connected in series with the seventh valve unit.

22. The converter according to claim 20, characterized in that, The fully controlled valve includes a one-way fully controlled switch, and / or a two-way fully controlled switch, and / or a module series switch; wherein... The unidirectional fully controlled switch includes several unidirectional fully controlled devices connected in series; The bidirectional fully controlled switch includes several bidirectional fully controlled devices or bidirectional fully controlled modules connected in series; The module series switch includes several fully controlled sub-modules connected in series.

23. The converter according to claim 22, characterized in that, The full control submodule includes at least one of the following: Half-bridge submodule, full-bridge submodule, near-full-bridge submodule, midpoint clamping submodule, dual half-bridge series submodule, dual full-bridge series submodule, clamping twin submodule, cross-connected twin submodule, self-resisting submodule, or diode clamping submodule.

24. The converter according to claim 22, characterized in that, The fully controlled submodule includes a capacitor and / or a battery.

25. The converter according to claim 22, characterized in that, The full-bridge circuit also includes a second surge arrester, which is connected in parallel with the full control valve, a plurality of the unidirectional full control devices, a plurality of the bidirectional full control devices, a plurality of the bidirectional full control modules, or a plurality of the full control sub-modules.

26. The converter according to claim 1, characterized in that, The common terminal of the upper and lower bridge arm circuits serves as the phase output terminal and is connected to the AC system via a transformer or reactor.

27. The converter according to claim 26, characterized in that, The converter also includes a voltage source converter. When the main circuit includes a three-phase bridge arm circuit, the voltage source converter adopts a three-phase star connection or delta connection circuit, and is connected in parallel with the three phases of the main circuit at the phase output terminal.

28. The converter according to claim 1, characterized in that, The converter also includes an energy storage circuit, one end of which is connected to the anode bus and the other end of which is connected to the cathode bus; wherein, the energy storage circuit includes a module series switch.

29. A control method for a converter, characterized in that, The method for controlling a converter as described in any one of claims 1 to 28 includes: When the operating state of the converter meets the transfer conditions, a switching control command is generated; The target auxiliary circuit corresponding to the bridge arm to be turned off in the converter is turned on according to the switching control command, so as to switch the current of the bridge arm to be turned off to the target auxiliary circuit. When the bridge arm to be turned off is restored to the off state, a turn-off command is generated. According to the turn-off command, the target auxiliary circuit is controlled to output a commutation voltage to the bridge arm to be turned on, so as to realize the commutation operation from the bridge arm to be turned off to the bridge arm to be turned on.

30. The method according to claim 29, characterized in that, The target auxiliary circuit includes a target transfer circuit, a target isolation circuit, and a full-bridge circuit corresponding to the bridge arm to be turned off. The step of activating the target auxiliary circuit corresponding to the bridge arm to be turned off in the converter according to the switching control command includes: The target transfer circuit and the target isolation circuit are turned on according to the switching control command, and the full-bridge circuit is controlled to generate a commutation voltage so that the current of the bridge arm to be turned off is switched to the target auxiliary circuit.

31. The method according to claim 29, characterized in that, The target auxiliary circuit includes a target transfer circuit, a target isolation circuit, and a full-bridge circuit corresponding to the bridge arm to be turned off. The step of activating the target auxiliary circuit corresponding to the bridge arm to be turned off in the converter according to the switching control command includes: According to the switching control command, the target transfer circuit, the target isolation circuit, and the full-bridge circuit are turned on, the full control valve of the bridge arm to be turned off is turned off, and the full control valve is controlled to generate a commutation voltage so that the current of the bridge arm to be turned off is switched to the target auxiliary circuit.

32. The method according to claim 29, characterized in that, When the bridge arm to be turned off is restored to off, the generation of a turn-off command includes: The shutdown command is generated when the reverse recovery time of a single valve in the bridge arm to be shut down is greater than or equal to the reverse recovery time of the thyristor in the single valve.

33. The method according to claim 29, characterized in that, The method further includes: During the non-commutation period of the converter, the isolation circuit and / or the transfer circuit corresponding to the non-conducting bridge arm of the converter are controlled to be turned on, so as to charge or discharge the fully controlled submodule of the single valve in the full bridge circuit of the converter.

34. The method according to claim 29, characterized in that, The method further includes: The voltage balance of the full-bridge circuit is maintained by charging and discharging different fully controlled sub-modules in the full-bridge circuit through DC-side control.

35. The method according to claim 29, characterized in that, When the converter is operating normally, the method further includes: If the capacitor voltage of the full-bridge circuit of the converter is less than a first preset value, the shutdown command is generated in advance. If the capacitor voltage of the full-bridge circuit of the converter is greater than a second preset value, the shutdown command is generated with a delay.

36. The method according to claim 29, characterized in that, The transfer conditions include at least one of the following: The converter commutates when the reference value of the shut-off angle is less than the minimum shut-off angle in the inverter state. The converter commutates when the reference firing angle value is less than the minimum firing angle under rectified conditions. The converter commutates when a commutation fault occurs in the inverter state.

37. The method according to claim 29, characterized in that, The converter adopts a grid-based control strategy.

38. The method according to claim 29, characterized in that, If the converter further includes an energy storage circuit, the method further includes: The energy storage circuit is controlled to charge and discharge, enabling the converter to interact with the AC system.

39. The method according to claim 29, characterized in that, The method further includes: In the event of a fault in the auxiliary circuit of the converter, disconnect the first disconnecting switch or the first disconnector between the fifth valve unit of the upper bridge isolation circuit and the bus in the converter, and disconnect the second disconnecting switch or the second disconnector between the sixth valve unit of the lower bridge isolation circuit and the bus in the converter.

40. A converter control device, characterized in that, The means for controlling a converter as described in any one of claims 1 to 28, the means comprising: The instruction generation module is used to generate switching control instructions when the converter meets the switching conditions; The switching module is used to turn on the target auxiliary circuit corresponding to the bridge arm to be turned off in the converter according to the switching control command, so as to switch the current of the bridge arm to be turned off to the target auxiliary circuit. The commutation module is used to generate a turn-off command when the bridge arm to be turned off is restored to the turn-off state, and control the target auxiliary circuit to output a commutation voltage to the bridge arm to be turned on according to the turn-off command, so as to realize the commutation operation from the bridge arm to be turned off to the bridge arm to be turned on.

41. A high-voltage direct current transmission system, characterized in that, At least one converter in the high-voltage direct current transmission system is a converter as described in any one of claims 1 to 28.

42. The system according to claim 41, characterized in that, The high-voltage direct current transmission system includes a two-terminal direct current transmission system or a multi-terminal direct current transmission system.

43. The system according to claim 42, characterized in that, The high-voltage direct current transmission system includes a single-pole direct current transmission system, a bipolar direct current transmission system, or a back-to-back direct current transmission system.

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