Fault ride-through circuit and method for an active voltage regulator

Abstract

The present application relates to the technical field of flexible direct current transmission, and particularly provides a fault ride-through circuit and a fault ride-through method of an active voltage regulator, aiming at solving the technical problem of fault ride-through of the active voltage regulator, comprising: the fault ride-through circuit comprises a converter transformer and an active voltage regulator; a positive output end of an inverter side of the active voltage regulator is connected to a lowermost end of a first winding of the converter transformer; the positive output end of the inverter side of the active voltage regulator is connected to a second winding of the converter transformer through a fast switch device; a negative output end of the inverter side of the active voltage regulator is grounded; a rectifier side of the active voltage regulator is connected to both ends of the second winding of the converter transformer through a power extraction transformer. The scheme designs a reasonable active voltage regulator AC fault ride-through current, which can smoothly exit the active voltage regulator without affecting the operation of the converter transformer during a serious fault of an external AC system, and is re-put into operation after the fault ends.

Description

Technical Field

[0001] The present invention relates to the field of DC system voltage regulation, and in particular to a fault ride-through circuit and a fault ride-through method of an active voltage regulator. Background Art

[0002] The converter transformer is the core of the HVDC transmission system. To meet the needs of DC system voltage regulation, a mechanical on-load tap changer is installed within the converter transformer. By adjusting the number of turns on the converter transformer's high-voltage winding, the voltage on the valve-side winding is regulated. However, the mechanical structure of the on-load tap changer is extremely complex. During long-term operation, frequent adjustments to the switch position are required, which can easily lead to various mechanical failures and pose the risk of inter-turn short circuits in the converter transformer. Numerous safety incidents caused by on-load tap changers in ultra-high voltage converter transformers have occurred, posing a significant challenge to the safe operation of ultra-high voltage DC systems.

[0003] Active voltage regulation, based on power electronics, regulates the voltage across the grid-side winding of the converter transformer by controlling the output voltage of the active voltage regulator, thereby regulating the voltage on the valve-side winding. Power electronics offer flexible control, unlimited actuation times, and fast response. They can quickly support voltage drops during system voltage drops, thus preventing DC system commutation failures. This represents a new development direction for on-load voltage regulation in converter transformers. Currently, a technical solution has been developed that uses active voltage regulators to replace traditional transformer taps. These active voltage regulators draw energy from the secondary winding of the converter transformer. The voltage regulation function is implemented by a cascaded AC / AC converter. By adjusting the potential at the bottom end of the first winding, the voltage across the first winding is altered, achieving the desired effect of regulating the valve-side voltage.

[0004] However, when a severe voltage drop occurs in the AC or DC system to which the active voltage regulator is connected, it may cause overcurrent or overvoltage in the active voltage regulator. Therefore, it is urgent to design a reasonable AC fault ride-through structure for the active voltage regulator. Summary of the Invention

[0005] In order to overcome the above-mentioned defects, the present invention provides a fault ride-through circuit and a fault ride-through method for an active voltage regulator.

[0006] In a first aspect, a fault ride-through circuit of an active voltage regulator is provided, wherein the fault ride-through circuit of the active voltage regulator comprises: a converter transformer and an active voltage regulator;

[0007] The inverter-side positive output terminal of the active voltage regulator is connected to the lowermost end of the first winding of the converter transformer;

[0008] The inverter-side positive output terminal of the active voltage regulator is connected to the second winding of the converter transformer via a fast switching device;

[0009] The negative output terminal of the inverter side of the active voltage regulator is grounded or grounded via a small impedance;

[0010] The rectifier side of the active voltage regulator is connected to both ends of the second winding of the converter transformer through an energy extraction transformer.

[0011] Preferably, the fast switching device includes at least one of the following: a thyristor bypass switch, an insulated gate bipolar transistor, a fast switch, and a thyristor bypass switch parallel circuit breaker.

[0012] Preferably, the converter transformer consists of a first winding, a second winding, a third winding and a tap.

[0013] Furthermore, both ends of the third winding are connected to the DC system through a converter valve.

[0014] Preferably, the active voltage regulator comprises: an AC / AC series branch, an energy extraction transformer and a bypass switch device;

[0015] The negative output terminal of the inverter side of the AC / AC series branch is grounded;

[0016] The inverter-side positive output terminal of the AC / AC series branch is connected to the lowermost end of the first winding of the converter transformer;

[0017] A bypass switch device is connected between the rectifier-side negative output terminal of the AC / AC series branch and the inverter-side positive output terminal of the AC / AC series branch;

[0018] The rectifier side of the AC / AC series branch is connected to both ends of the second winding of the converter transformer through an energy extraction transformer.

[0019] Furthermore, the AC / AC series branch is composed of multiple AC / AC units, wherein the AC / AC unit consists of a first branch, a second branch, a third branch, a fourth branch and a fifth branch connected in parallel in sequence, the first branch, the second branch, the fourth branch and the fifth branch are each composed of two power modules connected in series, and the third branch is a capacitor branch.

[0020] Furthermore, the connection point between the two power modules connected in series in the first branch and the connection point between the two power modules connected in series in the second branch are respectively the positive and negative output terminals of the rectifier side of the AC / AC unit; the connection point between the two power modules connected in series in the fourth branch and the connection point between the two power modules connected in series in the fifth branch are respectively the positive and negative output terminals of the inverter side of the AC / AC unit; the rectifier sides of all AC / AC units in the AC / AC series branch are the rectifier side of the AC / AC series branch; the inverter side positive output terminal of the first AC / AC unit in the AC / AC series branch is the inverter side positive output terminal of the AC / AC series branch; and the inverter side negative output terminal of the last AC / AC unit in the AC / AC series branch is the inverter side negative output terminal of the AC / AC series branch.

[0021] Furthermore, the bypass switch device includes at least one of the following: a circuit breaker, a contactor, an IGBT, a fast switch, and a TBS parallel circuit breaker.

[0022] Preferably, the inverter-side positive output terminal of the active voltage regulator is connected to any point between the two ends of the second winding of the converter transformer through a fast switching device.

[0023] In a second aspect, the present invention provides a fault ride-through method based on the fault ride-through circuit of the active voltage regulator, the method comprising:

[0024] Turn on the fast switching device and block the active voltage regulator, or turn on the bypass switching device.

[0025] Preferably, before turning on the fast switching device and locking the active voltage regulator, the method includes: adjusting the tap to a gear corresponding to the tap gear instruction issued by the DC system.

[0026] The above one or more technical solutions of the present invention have at least one or more of the following beneficial effects:

[0027] The present invention provides a fault ride-through circuit and method for an active voltage regulator. The fault ride-through circuit comprises: a converter transformer and an active voltage regulator; the inverter-side positive output terminal of the active voltage regulator is connected to the lowest end of the first winding of the converter transformer; the inverter-side positive output terminal of the active voltage regulator is connected to the second winding of the converter transformer via a fast switching device; the inverter-side negative output terminal of the active voltage regulator is grounded; and the rectifier side of the active voltage regulator is connected to both ends of the second winding of the converter transformer via an energy extraction transformer. This technical solution can deactivate the active voltage regulator in the event of a serious external fault, thereby preventing overcurrent and overvoltage issues in the voltage regulator. Furthermore, deactivating the voltage regulator will not affect the operation of the converter transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a main structural block diagram of a fault ride-through circuit of an active voltage regulator according to an embodiment of the present invention;

[0029] Figure 2 Schematic diagram of a single AC / AC structure inside the active voltage regulator in this embodiment;

[0030] Figure 3 1 is a schematic diagram of a path after the active voltage regulator is locked when the active voltage regulator in this embodiment adopts a strategy of turning on the fast switching device and locking the active voltage regulator to perform fault escape;

[0031] Figure 4 1 is a schematic diagram of a path after the active voltage regulator is locked when the active voltage regulator adopts a conduction bypass switch device strategy to perform fault escape in this embodiment. DETAILED DESCRIPTION

[0032] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0034] See attached Figure 1 , Figure 1 A fault ride-through circuit of an active voltage regulator according to an embodiment of the present invention specifically includes: a converter transformer and an active voltage regulator;

[0035] The inverter-side positive output terminal of the active voltage regulator is connected to the lowermost end of the first winding of the converter transformer;

[0036] The inverter-side positive output terminal of the active voltage regulator is connected to the second winding of the converter transformer via a fast switching device;

[0037] The negative output terminal of the inverter side of the active voltage regulator is grounded or grounded via a small impedance;

[0038] The rectifier side of the active voltage regulator is connected to both ends of the second winding of the converter transformer through an energy extraction transformer.

[0039] In this embodiment, the inverter-side positive output terminal of the active voltage regulator is connected to any point between the two ends of the second winding of the converter transformer through a fast switching device.

[0040] In one embodiment, any point between the two ends of the second winding can be a tap on the second winding. If the bottom end of the first winding of the converter transformer in the DC system voltage regulation system is connected to the tap on the second winding through a fast switching device, the tap can be adjusted to a gear corresponding to the tap gear instruction issued by the DC system.

[0041] In this embodiment, the fast switching device includes at least one of the following: a thyristor bypass switch, an insulated gate bipolar transistor, a fast switch, and a thyristor bypass switch parallel circuit breaker.

[0042] In this embodiment, the converter transformer consists of a first winding, a second winding, a third winding and a tap.

[0043] In this embodiment, both ends of the third winding are connected to the DC system through a converter valve.

[0044] In this embodiment, the active voltage regulator includes: an AC / AC series branch, an energy extraction transformer, and a bypass switch device;

[0045] The negative output terminal of the inverter side of the AC / AC series branch is grounded;

[0046] The inverter-side positive output terminal of the AC / AC series branch is connected to the lowermost end of the first winding of the converter transformer;

[0047] A bypass switch device is connected between the rectifier-side negative output terminal of the AC / AC series branch and the inverter-side positive output terminal of the AC / AC series branch;

[0048] The rectifier side of the AC / AC series branch is connected to both ends of the second winding of the converter transformer through an energy extraction transformer.

[0049] Wherein, the AC / AC series branch is composed of multiple AC / AC units, such as Figure 2 As shown, the AC / AC unit consists of a first branch, a second branch, a third branch, a fourth branch and a fifth branch connected in parallel in sequence, the first branch, the second branch, the fourth branch and the fifth branch are each composed of two power modules connected in series, and the third branch is a capacitor branch.

[0050] Furthermore, the connection point between the two power modules connected in series in the first branch and the connection point between the two power modules connected in series in the second branch are respectively the positive and negative output terminals of the rectifier side of the AC / AC unit; the connection point between the two power modules connected in series in the fourth branch and the connection point between the two power modules connected in series in the fifth branch are respectively the positive and negative output terminals of the inverter side of the AC / AC unit; the rectifier sides of all AC / AC units in the AC / AC series branch are the rectifier side of the AC / AC series branch; the inverter side positive output terminal of the first AC / AC unit in the AC / AC series branch is the inverter side positive output terminal of the AC / AC series branch; and the inverter side negative output terminal of the last AC / AC unit in the AC / AC series branch is the inverter side negative output terminal of the AC / AC series branch.

[0051] The bypass switch device includes at least one of the following: a circuit breaker, a contactor, an IGBT, a fast switch, and a TBS parallel circuit breaker.

[0052] Based on the above-mentioned fault ride-through circuit of the active voltage regulator, the present invention further provides a fault ride-through method based on the fault ride-through circuit of the active voltage regulator, the method comprising:

[0053] Turn on the fast switching device and block the active voltage regulator, or turn on the bypass switching device.

[0054] Preferably, before turning on the fast switching device and locking the active voltage regulator, the method includes: adjusting the tap to a gear corresponding to the tap gear instruction issued by the DC system.

[0055] In one embodiment, Figure 2 The structure shown is used as an application scenario. Figure 2 In the application scenario shown, when a fault occurs, the connection point between the fast switch device and the second winding is moved to a specified position, which can be determined based on the tap position command sent by the DC system to the second winding. After that, the voltage regulator is locked and a trigger signal for the fast switch device is sent. The first winding and the second winding jointly supply power to the converter valve side, as shown in the attached figure. Figure 3 As shown;

[0056] If the AC bus fault voltage drops deeply, close to metal grounding, the connection point between the fast switch device and the second winding can be directly moved to point P1 or P2 when the fault breaks out. After that, the voltage regulator is locked and a trigger signal for the fast switch device is issued. The first winding and the second winding jointly supply power to the converter valve side. Alternatively, after determining that the fast switch device is in the off state, the bypass switch device can be directly triggered, and only the first winding supplies power to the converter valve side.

[0057] If the fast switch device refuses to operate during the above process, the bypass switch device can be directly triggered after the fast switch device is determined to be in the off state during fault travel, and only the first winding supplies power to the converter valve side. Figure 4 shown.

[0058] After the fault is restored, unlock the voltage regulator and stop sending the trigger signal of the fast switch device or stop triggering the bypass switch device. If the fast switch or bypass switch device refuses to operate during this process, the active voltage regulator should be locked after confirming the refusal to operate.

[0059] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0060] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0061] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0062] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1A step that specifies a function in one or more boxes.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A fault ride-through circuit for an active voltage regulator, characterized in that: The fault ride-through circuit includes: a converter transformer and an active voltage regulator; The inverter-side positive output terminal of the active voltage regulator is connected to the lowermost end of the first winding of the converter transformer; The inverter-side positive output terminal of the active voltage regulator is connected to the second winding of the converter transformer via a fast switching device; The negative output terminal of the inverter side of the active voltage regulator is grounded or grounded via a small impedance; The rectifier side of the active voltage regulator is connected to both ends of the second winding of the converter transformer through an energy-taking transformer; The fault ride-through method based on the fault ride-through circuit of the active voltage regulator includes: turning on a fast switching device and locking the active voltage regulator, or turning on a bypass switching device.

2. The fault ride-through circuit according to claim 1, wherein: The fast switching device includes at least one of the following: a thyristor bypass switch, an insulated gate bipolar transistor, a fast switch, and a thyristor bypass switch parallel circuit breaker.

3. The fault ride-through circuit according to claim 1, wherein: The converter transformer consists of a first winding, a second winding, a third winding and a tap.

4. The fault ride-through circuit according to claim 3, wherein: The two ends of the third winding are connected to the DC system through a converter valve.

5. The fault ride-through circuit according to claim 1, wherein: The active voltage regulator includes: an AC / AC series branch, an energy-taking transformer, and a bypass switch device; The negative output terminal of the inverter side of the AC / AC series branch is grounded; The inverter-side positive output terminal of the AC / AC series branch is connected to the lowermost end of the first winding of the converter transformer; A bypass switch device is connected between the rectifier-side negative output terminal of the AC / AC series branch and the inverter-side positive output terminal of the AC / AC series branch; The rectifier side of the AC / AC series branch is connected to both ends of the second winding of the converter transformer through an energy extraction transformer.

6. The fault ride-through circuit according to claim 5, wherein: The AC / AC series branch is composed of multiple AC / AC units, wherein the AC / AC unit consists of a first branch, a second branch, a third branch, a fourth branch and a fifth branch connected in parallel in sequence, the first branch, the second branch, the fourth branch and the fifth branch are each composed of two power modules connected in series, and the third branch is a capacitor branch.

7. The fault ride-through circuit according to claim 6, wherein: The connection point between the two power modules connected in series in the first branch and the connection point between the two power modules connected in series in the second branch are respectively the positive and negative output terminals of the rectifier side of the AC / AC unit; the connection point between the two power modules connected in series in the fourth branch and the connection point between the two power modules connected in series in the fifth branch are respectively the positive and negative output terminals of the inverter side of the AC / AC unit; the rectifier sides of all AC / AC units in the AC / AC series branch are the rectifier side of the AC / AC series branch; the inverter side positive output terminal of the first AC / AC unit in the AC / AC series branch is the inverter side positive output terminal of the AC / AC series branch; and the inverter side negative output terminal of the last AC / AC unit in the AC / AC series branch is the inverter side negative output terminal of the AC / AC series branch.

8. The fault ride-through circuit according to claim 5, wherein: The bypass switch device includes at least one of the following: a circuit breaker, a contactor, an IGBT, a fast switch, and a TBS parallel circuit breaker.

9. The fault ride-through circuit according to claim 1, wherein: The inverter-side positive output terminal of the active voltage regulator is connected to any point between the two ends of the second winding of the converter transformer through a fast switching device.

10. The fault ride-through circuit according to claim 1, wherein: Before turning on the fast switching device and locking the active voltage regulator, the method includes adjusting the tap to a gear corresponding to the tap gear instruction issued by the DC system.

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