Transient characteristic of mode-conversion strategy for pumped storage machines based on eco-friendly generator circuit breaker and phase reversal disconnecting switch

The generator circuit breaker is a special breaker located between a pumped storage machine and a step-up transformer. The first requirement for generator circuit breaker is to interrupt fault currents with delayed current zero, preventing the damage of pumped storage machine and transformer caused by fault current. The second requirement for generator circuit breaker is to interrupt load current frequently, realizing the frequent mode conversion of pumped storage machine from generator-mode to motor-mode. Up to now, SF₆ gas which is a potent greenhouse gas has been widely used in large-capacity generator circuit breaker. To seek eco-friendly alternatives of generator circuit breaker, the contributions of this paper are: (1) an eco-friendly generator circuit breaker based on a fast vacuum switch and a power electronic damping module is proposed in this paper. (2) Considering fast vacuum switch has a short mechanical operating life (2000 ∼ 5000 operations), to avoid the operating of fast vacuum switch in generator circuit breaker, a mode-conversion strategy based on the cooperation of power electronic damping module in eco-friendly generator circuit breaker and phase reversal disconnecting switch is proposed in this paper. Through the analysis of voltage phasors, the transient characteristics of the mode-conversion strategy are revealed to demonstrate the applicable scope of the proposed mode-conversion strategy for pumped storage machine. Simulation verifications are elaborated in PSCAD.