Research on a current commutation drive circuit for hybrid dc circuit breaker and its optimisation design

Abstract

Hybrid direct current circuit breakers (DCCBs) have great prospects for the isolation of dc faults in multi-terminal dc grids. Current commutation from the mechanical switch branch to the static DCCB branch is the precondition to interrupt fault currents successfully for the hybrid DCCBs. A current commutation drive circuit (CCDC) is presented in this study, and it has features of low cost, low operating losses and free maintenance. Experiments have been carried out on a unidirectional 44 kV hybrid DCCB prototype with CCDC. The results show the current of 3.4 kA can be commutated by CCDC within 130 μs, and be interrupted successfully within 2 ms. For a bidirectional 80 kV hybrid DCCB cell, the effectiveness of CCDC is validated with simulations carried out in PACAD. Then, an index is defined to represent the current commutation capability of CCDC and a mathematical model for CCDC is established to calculate the index. To reduce the cost of CCDC with certain current commutation capability, an optimisation method based on genetic algorithm is proposed in this study. According to the optimisation results of CCDC suitable for bidirectional 80 kV hybrid DCCB cell, the cost of CCDC has been reduced by optimisation.