Topology Simplification and Parameter Design of Z/T/Γ-Source Circuit Breakers

Z/T/ $\Gamma $ -source circuit breakers used in flexible dc distribution systems have been rapidly developed due to their advantages of high speed and low cost. However, the precise model of the circuit breaker is generally a high-order circuit, which is difficult to solve. The lack of simplified topology and parameter design considering system parameters (line inductance, line resistance, and load capacitance) restricts their applications in practical engineering. Therefore, based on the equivalent mathematical model, a simplified topology that can represent Z/T/ $\Gamma $ -source circuit breakers is proposed and their working principles are revealed in this article. Considering system parameters, the parameters of Z/T/ $\Gamma $ -source circuit breakers are designed to take care of short circuit fault and step changes in load. Finally, simulation and experiment show that parameters designed by the proposed method can ensure the reliable operation for Z/T/ $\Gamma $ -source circuit breakers.

I. Introduction

The renewable energy, dc loads, and storage batteries can be connected to flexible dc distribution networks more easily than ac network. dc network has simpler control strategies without considering frequency and phase angle. It can collect, store, and transmit power in an efficient way to cope with the increasing dc loads. With the development of dc systems, short circuit protection has gradually become the focus of research. dc circuit breakers (DCCBs) can reliably cutoff the fault current, prevent the converters from overcurrent, and minimize the fault area. However, they are faced with the problems of high cost and low speed nowadays.