Topology and Parameter Design of the Resistance-Capacitance Hybrid DC Circuit Breaker with Coupling Reactors

Abstract

DC circuit breakers are the important apparatus of the medium-voltage DC distribution system. In order to limit the fault current and Shorten the whole breaking time, the paper proposes a novel resistive and capacitive type current-limiting medium voltage DC circuit breaker with coupling reactor (MDCB). The primary and the second inductor $(L_{1},\\ L_{2})$ of coupling reactor are connected to main branch and the high speed switch in series respectively, which is used to limit the fault current and improve the current commutation. The resistance-capacitance element is connected in series with the solid switch unit, which is used to limit the current and decrease the dissipation time of the MOV. This structure can accelerate the current commutation and limit the peak fault current. The influence of the coupling reactor and the resistance-capacitance element on the working process is analyzed and the reference of the parameters design is obtained. The model is established by the MATLAB/Simulink. The influence law of coupling reactor and resistance-capacitance element parameters on commutation time, current limiting effect, and complete shutdown time is gained. The proper parameters of the coupling reactor are as follows: the primary inductor L i is about $250\\sim 300\\mu H$, the second inductor L2 is about $50\\sim 100\\mu H$ and the coupling coefficient k is about $0.95\\sim 0.98$,When the resistance and capacitance parameters R and C are in the range of $0.1\\sim 0.2\\Omega$ and $ 20\\sim 50\\mu$F, the current commutation time is shortened from 1. 5ms to 0. 5ms, the fault current peak value is reduced by 47.1%, the entire shutdown time has been shortened by 1.9ms, and preliminary experiments have been conducted to verify the feasibility of the new topology, which provides a reference for independent research and development of high-performance medium-voltage DC circuit breakers.