A medium-voltage large-capacity hybrid DC circuit breaker and its current-limiting breaking method

Abstract

The invention discloses a medium voltage large capacity hybrid DC circuit breaker. A quick breaking module, a primary transfer module, a secondary transfer module and an energy absorbing module are connected in parallel and are then connected in series with an isolation module, the quick breaking module and the isolation module are connected in series to carry a load current of a DC system in normal operation, and the isolation module is used for breaking the normal operation current. The current limiting breaking method is further disclosed, when a short-circuit fault occurs in a DC power system, an arc voltage generated by the quick breaking module makes the current flowing through the quick breaking module transfer to the primary transfer module, the primary transfer module automatically generates a relatively high arc voltage, the fault current is forced to quickly transfer to the secondary transfer module, and lastly, breaking is achieved. The medium voltage large capacity hybridDC circuit breaker is advantaged in that low long-term load loss is low, the current transfer speed of the high current breaking process can be greatly improved, the shutdown current of the secondarytransfer module is reduced, control of the liquid metal is not needed, and effective limitation on the fault current is achieved quickly and reliably.

Description

technical field [0001] The invention belongs to the technical field of circuit breakers, and in particular relates to a medium-voltage large-capacity hybrid DC circuit breaker and its current-limiting breaking method. Background technique [0002] The rapid development of flexible DC transmission technology has greatly increased its capacity, with higher rated current and smaller line impedance. When a short-circuit fault occurs, the peak value of the short-circuit current is as high as hundreds of kA, and the short-circuit current rises at a higher rate. Traditional power system protection equipment takes a long time to operate and has limited breaking capacity, making it difficult to achieve rapid current-limited breaking of short-circuit currents. If the short-circuit current is not cut off in time, it will cause permanent damage to electrical equipment, so it is urgent to conduct research on new current limiting and breaking technology. [0003] The current DC circuit b...

AI Technical Summary

Problems solved by technology

[0004] 1. The high-current arc extinguishing problem of mechanical circuit breakers leads to long insulation recovery time, which makes it difficult to directly break high-current, low breaking reliability and short service life

[0005] 2. The number of power electronic devices used in solid-state circuit breakers is large in series, and the on-state loss is large. Special cooling equipment is required, and the system is complex.

[0006] 3. The liquid metal current limiter can only limit the peak value of the short-circuit current, and does not have the ability to break large currents

[0007] 4. A hybrid circuit breaker composed of a mechanical circuit breaker and a solid-state circuit breaker is used. The arc voltage generated by the mechanical circuit breaker is low when it is switched off, and a multi-stage commutation process is required. The commutation process is long and the control system is complicated; In high-voltage applications, the loop inductance is large, the transfer speed is slow, limited by the level of semiconductors, the breaking capacity is low, or a large number of series and parallel connections are required, which is large in size and high in cost

[0010] If a semiconductor switch is used as an intermediate link, due to the low arc voltage, large loop inductance, high on-state impedance of the semiconductor switch, and slow current transfer speed, the semiconductor switch cannot be turned off reliably in the end, or multiple devices need to be connected in series. Parallel connection will greatly increase the volume and cost

[0011] In the existing active current transfer hybrid circuit breaker, the mechanical switch of the main current path is connected in series with a semiconductor switch that can be turned off. Due to the high conduction loss of the semiconductor switch, additional heat dissipation equipment is required, and the control is complicated, so it is not suitable for large currents. occasion

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