Research On Breaking Process Of HVDC Circuit Breaker With Forced Current Zero Formation And Optimized Energy Absorption Method

With large-scale renewable energy into grid, the intermittent and randomness of new energy become increasingly prominent. The multi-terminal DC system based on flexible HVDC technology is recognized as an effective method for this problem. Developing HVDC circuit breaker with larger capacity and higher speed is of great significance to developing multi-terminal DC grid. With the forced current zero formation HVDC circuit breaker for the research object, this paper has carried on simulation and experimental research on the breaking process.Firstly, this paper proposes a modular forced current zero formation HVDC circuit breaker topology with optimized energy-absorption method. By making comparison between the breaking process of rated current and short circuit fault current, it is found that the proposed optimized energy-absorption method can effectively reduce the peak voltage of circuit breaker elements and energy absorption capacity requirement.As the key arc-extinguishing component in forced current zero formation HVDC circuit breaker, the post-arc dielectric recovery process of vacuum chamber determines whether the circuit breaker can successfully complete the current commutation process and eventually break current. Through establishing vacuum post-arc sheath layer continuous transition model and metal vapor density attenuation model, this paper analyzes the influences of commutation velocity, peak circuit value and vacuum chamber contacts distance and discovers the relationships between circuit breaker parameters and vacuum chamber post-arc dielectric recovery process.Then, based on the post-arc dielectric recovery process of vacuum chamber, through analyzing the influence factors on the breaking process, such as commutation branch frequency, commutation capacitance and energy-absorption resistance value, this paper gets effect law of circuit breaker parameters on the current and voltage variations of vacuum chamber. What’s more, the design process of HVDC circuit breaker parameters is presented.Finally, through experiments on the HVDC circuit breaker single module prototype, this paper completes the low current and high current breaking experiments and finds that the changes of circuit parameters are in accordance with former analysis. By exploring influences of experimental parameters on the breaking results of HVDC circuit breaker, it is found that the breaking current peak value and commutation velocity will both affect the breaking results. At last, a brief analysis is conducted on the relationship between metal vapor density and different results of forced current zero formation HVDC circuit breaker.