A current-limiting controllable arrester, converter, power transmission system and control method

Abstract

The invention relates to a current-limiting type controllable arrester. The current-limiting type controllable arrester is composed of a first arrester and a variable arrester in series, and the variable arrester is composed of a second arrester and a bypass branch in parallel; the invention It also relates to a converter, a power transmission system and a control method including the above-mentioned current-limiting controllable arrester, which can quickly and accurately locate the single-pole grounding fault point, and quickly isolate the fault point, which greatly improves the operation reliability of the DC power transmission system.

Description

technical field [0001] The invention belongs to the application field of power electronics, and in particular relates to a current-limiting controllable arrester, a converter, a power transmission system and a control method. Background technique [0002] The flexible DC transmission system adopts a modular multi-level converter, which has many advantages, such as low requirements for consistent triggering of dynamic voltage equalization of devices, good scalability, high output voltage waveform quality, low switching frequency, and low operating loss. However, its shortcomings are also Obviously, once a line short-circuit fault occurs, it will soon affect the DC transmission network and the AC network, and the fault cannot be removed by shutting down the converter. Especially for a single-pole DC transmission system, after a single-phase grounding fault occurs, the fault current does not have a circulation path, and it is difficult to determine the location of the fault poi...

AI Technical Summary

Problems solved by technology

[0002] The flexible DC transmission system adopts modular multilevel converters, which have many advantages such as low requirements for consistent triggering of dynamic voltage equalization of devices, good scalability, high quality output voltage waveforms, low switching frequency, and low operating loss. Obviously, once a line short-circuit fault occurs, it will soon affect the DC transmission network and the AC network, and the fault cannot be removed by shutting down the converter

Especially for unipolar DC transmission systems, after a single-phase ground fault occurs, the fault current does not have a flow path, and it is difficult to determine the location of the fault point based on the fault current

For the multi-terminal flexible DC transmission system, once a single-pole grounding fault occurs, the ground voltage of the non-faulty poles of all converters in the system will be doubled, which will adversely affect the insulation of the equipment in the system. If the fault is not removed in time , may lead to equipment insulation breakdown. Since the location of the fault point cannot be determined and the fault cannot be removed quickly and accurately, all converter stations can only stop running. However, after the stop operation, the fault point can only be found manually. a long time

Patent 201310370589.X A multi-terminal flexible DC transmission system and fault control method proposes the use of non-linear resistors. When a single-phase ground fault occurs, limiting the ground voltage of non-ground electrodes is only a means of protection, and The operating voltage of the non-linear resistor is fixed, and the accuracy is not high. If the value is too small, it may cause misoperation, and frequent misoperation will affect the life of the equipment; the operating voltage is too large, such as 1.8 times the rated value. , after the non-linear resistor operates, the voltage is still too high, the insulation of the equipment will also be affected, and the fault current is still not obvious at this time, there are many problems in actual engineering applications

Patent 201710862244.4 is an overvoltage protection circuit and method for a DC circuit breaker. This patent uses a controllable arrester, and the controllable arrester is arranged near the DC switch to limit the overvoltage caused by the breaking of the DC switch. The controllable arrester is equipped with a current-limiting unit. During the breaking process of the DC switch, the converter can withstand long-term overcurrent, which is likely to cause equipment damage; The two ends of the fixed part of the surge arrester generate instantaneous overvoltage, thereby generating a large inrush current. On the one hand, the inrush current affects the life of the equipment, and on the other hand, it increases the design capacity of the arrester and greatly increases the cost.

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