AC-DC coordination protection method and device for circuit breaker in flexible DC power transmission converter station

Abstract

The invention relates to an alternating current and direct current coordinating protection method and device for a flexible high voltage direct current transmission converter station circuit breaker. The method and device are characterized in that the protection device for the flexible high voltage direct current transmission converter station circuit breaker is divided into an alternating current protection device body and a direct current protection device body, the alternating current protection device body and the direct current protection device body share out the work and cooperate with each other for remotely tripping a superior circuit breaker so as to protect the flexible high voltage direct current transmission converter station circuit breaker, an alternating protection area mainly comprises a connecting transformer T, an alternating current incoming line circuit breaker DL, an alternating current side disconnecting switch DS and an alternating current side current measurement unit CT, a direct current area mainly comprises two current converters, a start loop resistor R, a direct current side disconnecting switch DS, a smoothing reactor L of a direct current line, a bridge arm reactor L, a direct current measuring unit CT, a PT and a direct current side disconnecting switch DS. According to the alternating current and direct current coordinating protection method and device, the alternating current protection device body and the direct current protection device body are in seamless cooperation to remove a dead zone of protection of a converter station, the function of remotely tripping the superior circuit breaker is achieved under the situation that the converter station breaks down and the circuit breaker fails, the function of achieving circuit breaker failure protection is achieved, and the reliability of converter station control protection equipment is improved.

Description

technical field [0001] The invention relates to an AC-DC coordination protection method and device for a circuit breaker of a flexible direct current transmission converter station. It belongs to the technical field of direct current transmission equipment. Background technique [0002] At present, flexible DC transmission is based on voltage source converter and pulse width modulation technology to invert DC voltage into AC voltage with controllable amplitude and phase, which can independently and quickly control the transmitted active power and reactive power, and enhance the power transmission. It has become the most potential power transmission method to realize the stable connection between large-scale wind farms and the main grid. [0003] Such as figure 1 As shown, the conventional flexible direct current transmission converter station generally adopts the input and output mode of the line-to-transformer group, usually one end is connected to the output line of the ...

AI Technical Summary

Problems solved by technology

[0006] For faults in other areas of the DC side of the converter station, such as single-phase grounding of the DC pole line, internal short circuit in the valve area, etc., the conditions for increasing the current of the AC incoming line cannot be satisfied.

When a single-phase ground fault occurs on the DC side of the converter valve based on the voltage source converter, the DC protection action circuit breaker trips and locks the converter valve at the same time. In case of a short-circuit fault in the area, the current on the AC side is only about tens of amperes. After passing through the transformation ratio of CT (if it is 3200:1), it enters the circuit breaker failure protection device. Since the current criterion of the circuit breaker failure protection device is at least 0.08 Ampere, the secondary current after the transformation ratio is lower than the adjustable range of the protection, which cannot meet the start-up failure condition

In this case, the circuit breaker fails and refuses to operate, and the failure protection criterion does not meet the start-up long-distance jump condition, resulting in the upper-level circuit breaker not being able to trip correctly, which not only damages the expensive power electronic equipment of the converter station, but also expands the fault area

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