A novel current-limiting hybrid DC breaker based on thyristors

Abstract

Since the DC current has no zero-crossing in high-voltage and large-capacity DC scenarios, and the low line impedance results in a large growth rate of fault current, the breaking requirements of DC circuit breakers (DCCB) are further increased. Hybrid circuit breaker (HCB) represent the techniques orientation of high-voltage DC interruptions and the HCB can quickly interrupt fault currents to ensure reliable and safe operation of the grid, which is an indispensable piece of equipment in flexible DC systems. Utilizing the characteristics of thyristor with strong current capacity, low on-state loss and zero-crossing natural turn-off of unidirectional current, this article proposes a hybrid circuit breaker scheme based on forced zero-crossing of thyristors (T-HCB). The proposed T-HCB could achieve arcless breaking of mechanical switch (MS), which improves the service life of the MS. In addition, it has the limiting capability of fault current, which reduces the growth rate and amplitude of the fault current and improves the security level and economics of the system. Firstly, the working principle of the proposed topology is introduced and deduced. Then, the key parameters affecting the commutation capacity and current limiting capacity are analyzed extraordinary. Finally, a comparison of the breaking performance in a 4-terminal DC system with existing fault current limiter (FCL) and ABB hybrid DCCB demonstrates the feasibility and superiority of the proposed topology.