Low reactive power operation mode and method of direct current transmission converter valve
By monitoring and shutting off the current of the converter bridge arm in real time and using the buffer capacitor to absorb energy, a low reactive power operation mode is achieved, which solves the problem of increased reactive power demand of the converter valve under high arc extinction angle and reduces reactive power demand and commutation failure risk.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TSINGHUA UNIVERSITY
- Filing Date
- 2025-01-17
- Publication Date
- 2026-06-02
AI Technical Summary
Existing converter valves must operate at an arc-extinguishing angle of around 17°, which leads to increased reactive power demand and makes commutation failure more likely.
By monitoring the real-time conduction current of the converter bridge arm, when the current is less than the shutdown current, the shut-off valve string is turned off, and the energy is absorbed by the buffer capacitor, so that the voltage of the buffer capacitor is equal to the operating voltage of the surge arrester, thus achieving a low reactive power operation mode.
The arc-extinguishing angle of the converter valve has been reduced to 0 or even negative, thus reducing reactive power demand and the reactive power load on the converter valve power station.
Smart Images
Figure CN119787780B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of converter control technology, and in particular to a low reactive power operation mode and method for DC transmission converter valves. Background Technology
[0002] With the development of power systems, high voltage direct current (HVDC) transmission technology has become increasingly popular due to its advantages in long-distance and large-capacity power transmission. Among them, the traditional grid-commutated converter based high voltage direct current (LCC-HVDC) technology has even more obvious advantages in this regard.
[0003] The existing converter valve must operate at an arc-extinguishing angle of about 17°, otherwise commutation failure will occur, increasing the reactive power demand of the converter valve. Summary of the Invention
[0004] To address the aforementioned problems, the inventors have developed this invention, which, through specific implementation methods, provides a low reactive power operation mode and method for DC transmission converter valves.
[0005] In a first aspect, embodiments of the present invention provide a low reactive power operation mode for a DC transmission converter valve, wherein the bridge arm of the converter valve has a shut-off valve string, and the low reactive power operation mode is configured as follows:
[0006] The real-time on-current of the bridge arm of the converter is monitored in real time. When the real-time on-current of the bridge arm is less than the off-current, the corresponding turn-off valve string is turned off. When all the energy generated by the off-current on the converter reactance is absorbed by the buffer capacitor, the maximum voltage of the buffer capacitor is equal to the operating voltage of the surge arrester.
[0007] Furthermore, the converter includes multiple identical bridge arms, each bridge arm consisting of a series of shut-off tubes. Each shut-off tube series consists of m shut-off tubes connected in series, where m is a positive integer greater than 1. The anode of the preceding shut-off tube is connected in series with the cathode of the following shut-off tube. In the first bridge arm, the cathode of the shut-off tube at the first end of the shut-off tube series is connected to the positive terminal of the DC voltage, and the anode of the shut-off tube at the second end of the shut-off tube series is connected to the three-phase AC connection point. In the second bridge arm, the cathode of the shut-off tube at the first end of the shut-off tube series is connected to the three-phase AC connection point, and the anode of the shut-off tube at the second end of the shut-off tube series is connected to the negative terminal of the DC voltage.
[0008] Furthermore, each bridge arm also includes a thyristor valve string connected in series with the turn-off valve string. Each thyristor valve string consists of k thyristors connected in series, where k is an integer greater than or equal to 1. The anode of the preceding thyristor is connected in series with the cathode of the following thyristor. In the first bridge arm, the cathode of the thyristor valve string is connected to the positive terminal of the DC voltage, and the anode of the thyristor valve string is connected to the cathode of the turn-off valve string. In the second bridge arm, the cathode of the thyristor valve string is connected to the three-phase AC connection point, and the anode of the thyristor valve string is connected to the cathode of the turn-off valve string.
[0009] Secondly, embodiments of the present invention provide a method for low reactive power operation of a DC transmission converter valve, comprising:
[0010] Real-time monitoring of the on-state current of the bridge arm of the converter;
[0011] When the real-time on-current of the bridge arm is less than the off-current, the corresponding shut-off valve string is shut off. When the energy generated by the off-current on the commutator reactor is entirely absorbed by the buffer capacitor, the maximum voltage of the buffer capacitor is equal to the operating voltage of the surge arrester.
[0012] Furthermore, it also includes the following steps:
[0013] The shutdown current is determined based on the surge arrester voltage, commutation reactance, and buffer capacitor capacitance of the converter valve.
[0014] The beneficial effects of the above-mentioned technical solutions provided by the embodiments of the present invention include at least the following: the converter valve continuously operates in a low reactive power operation mode, which enables the current to be turned off before it naturally crosses zero. Therefore, the arc extinction angle of the converter valve can be reduced to 0 or even negative, thereby reducing the reactive power demand of the converter valve and reducing the reactive power of the converter valve power station.
[0015] Other features and advantages of the invention will be set forth in the following description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.
[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:
[0018] Figure 1 This is a flowchart of the method in an embodiment of the present invention;
[0019] Figure 2 This is a schematic diagram of a converter valve in one embodiment of the present invention;
[0020] Figure 3 This is a schematic diagram of another structure of the converter valve in an embodiment of the present invention;
[0021] Figure 4 The above are simulation diagrams of the release capacitor under currents of 250A and 400A in an embodiment of the present invention. Detailed Implementation
[0022] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
[0023] To address the problems existing in the prior art, embodiments of the present invention provide a low reactive power operation mode and method for DC transmission converter valves.
[0024] This invention provides a low reactive power operation mode for a DC transmission converter valve, wherein the bridge arm of the converter valve has a shut-off valve string, and the low reactive power operation mode is configured as follows:
[0025] The real-time on-current of the bridge arm of the converter is monitored in real time. When the real-time on-current of the bridge arm is less than the off-current, the corresponding turn-off valve string is turned off. When all the energy generated by the off-current on the converter reactance is absorbed by the buffer capacitor, the maximum voltage of the buffer capacitor is equal to the operating voltage of the surge arrester.
[0026] Optional, such as Figure 2 As shown, the converter includes multiple identical bridge arms, each bridge arm consisting of a series of turn-off tubes. Each series of turn-off tubes consists of m turn-off tubes connected in series, where m is a positive integer greater than 1. The anode of the preceding turn-off tube is connected in series with the cathode of the following turn-off tube. In the first bridge arm, the cathode of the turn-off tube at the first end of the series of turn-off tubes is connected to the positive terminal of the DC voltage, and the anode of the turn-off tube at the second end of the series of turn-off tubes is connected to the three-phase AC connection point. In the second bridge arm, the cathode of the turn-off tube at the first end of the series of turn-off tubes is connected to the three-phase AC connection point, and the anode of the turn-off tube at the second end of the series of turn-off tubes is connected to the negative terminal of the DC voltage.
[0027] Among them, a turn-off transistor refers to a device with self-turn-off function, that is, a power electronic device that can be controlled to both turn on and turn off by a control signal.
[0028] Preferably, the turn-off device may include, but is not limited to, GTO (Gate Turn-Off Thyristor), IGCT (Integrated Gate Commutated Thyristor), IGBT (Insulated Gate Bipolar Transistor), GTR (Power Transistor), MOSFET (Power Field Effect Transistor), etc.
[0029] Optional, such as Figure 3 As shown, each bridge arm further includes a thyristor valve string connected in series with the turn-off valve string. Each thyristor valve string consists of k thyristors connected in series, where k is an integer greater than or equal to 1. The anode of the preceding thyristor is connected in series with the cathode of the following thyristor. In the first bridge arm, the cathode of the thyristor valve string is connected to the positive terminal of the DC voltage, and the anode of the thyristor valve string is connected to the cathode of the turn-off valve string. In the second bridge arm, the cathode of the thyristor valve string is connected to the three-phase AC connection point, and the anode of the thyristor valve string is connected to the cathode of the turn-off valve string.
[0030] The converter valve operates continuously in a low reactive power mode, which allows the current to be shut off before it naturally crosses zero. Therefore, the arc-extinguishing angle of the converter valve can be reduced to 0 or even negative, thereby reducing the reactive power demand of the converter valve and reducing the reactive power of the converter valve power station.
[0031] Another embodiment of the present invention provides a method for low reactive power operation of DC transmission converter valves, such as... Figure 1 As shown, it includes the following steps:
[0032] Step S1: Monitor the real-time on-current of the bridge arm of the converter.
[0033] Step S2: When the real-time on-current of the bridge arm is less than the off-current, the corresponding shut-off valve string is turned off. When the energy generated by the off-current on the commutator reactor is completely absorbed by the buffer capacitor, the maximum voltage of the buffer capacitor is equal to the operating voltage of the surge arrester.
[0034] Specifically, such as Figure 4 As shown, at 400A, the overvoltage generated by the capacitor absorbing the turn-off energy is higher than the arrester's operating voltage, posing a risk of continuous operation of the arrester. However, at 250A, the overvoltage is lower than the arrester's operating voltage, allowing for continuous operation.
[0035] The method described in this embodiment further includes the following steps:
[0036] The shutdown current is determined based on the surge arrester voltage, commutation reactance, and buffer capacitor capacitance of the converter valve.
[0037] The method described in this embodiment monitors the real-time on-current of the bridge arm of the converter. When the real-time on-current of the bridge arm is less than the off-current, the corresponding shut-off valve string is turned off, which enables the current to be turned off before it naturally crosses zero. Therefore, the arc-extinguishing angle of the converter valve can be reduced to 0 or even negative, thereby reducing the reactive power demand of the converter valve and reducing the reactive power of the converter valve power station.
[0038] Any modifications, additions, and equivalent substitutions made within the scope of the principles of this invention shall still fall within the patent coverage of this invention.
[0039] Unless otherwise stated, the term "connection" as used above refers to a logical relationship of current transmission and does not necessarily indicate a direct electrical connection. Furthermore, terms such as "first" and "second" do not indicate a sequential order but are merely used to identify related units or devices.
Claims
1. A method for low reactive power operation of a DC transmission converter valve, characterized in that, The method includes the following steps: The shutdown current is determined based on the surge arrester voltage, commutator reactance, and buffer capacitor capacitance of the converter valve. Real-time monitoring of the on-state current of the converter's bridge arms; When the real-time on-current of the bridge arm is less than the off-current, the corresponding shut-off valve string is shut off before the real-time on-current of the bridge arm naturally overcurrents, so that the DC transmission converter valve continues to operate in a low reactive power operation mode. Wherein, when all the energy generated by the turn-off current on the commutator reactor is absorbed by the buffer capacitor, the maximum voltage of the buffer capacitor is equal to the operating voltage of the surge arrester.
2. The low reactive power operation method for DC transmission converter valves as described in claim 1, characterized in that, The converter includes multiple identical bridge arms, each bridge arm consisting of a series of turn-off transistors. Each series of turn-off transistors consists of m turn-off transistors connected in series, where m is a positive integer greater than 1. The anode of the preceding turn-off transistor is connected in series with the cathode of the following turn-off transistor. In the first bridge arm, the cathode of the turn-off transistor at the first end of the series of turn-off transistors is connected to the positive terminal of the DC voltage, and the anode of the turn-off transistor at the second end of the series of turn-off transistors is connected to the three-phase AC connection point. In the second bridge arm, the cathode of the turn-off transistor at the first end of the series of turn-off transistors is connected to the three-phase AC connection point, and the anode of the turn-off transistor at the second end of the series of turn-off transistors is connected to the negative terminal of the DC voltage.
3. The low reactive power operation method for DC transmission converter valves as described in claim 2, characterized in that, Each bridge arm also includes a thyristor valve string connected in series with the turn-off valve string. Each thyristor valve string consists of k thyristors connected in series, where k is an integer greater than or equal to 1. The anode of the preceding thyristor is connected in series with the cathode of the following thyristor. In the first bridge arm, the cathode of the thyristor valve string is connected to the positive terminal of the DC voltage, and the anode of the thyristor valve string is connected to the cathode of the turn-off valve string. In the second bridge arm, the cathode of the thyristor valve string is connected to the three-phase AC connection point, and the anode of the thyristor valve string is connected to the cathode of the turn-off valve string.