Short-Circuit Fault Protection Scheme for Serial-Shunt Type Soft Normally Open Point

Soft normally-open points (SNOPs) are power electronic devices installed in place of normally-open points in the distribution network, which enables the control of real and reactive power flows between each end-point of its installation sites. The conventional SNOP topology is implemented with a back-to-back voltage source converter (BTB-VSC), which is flawed in bulky size, high cost, and low efficiency. To solve these problems, a serial-shunt type SNOP is proposed to achieve higher power density, lighter weight, and flexible scalability. However, feeders and switching devices are easily damaged under a short- circuit fault due to the serial-shunt structure of SS-SNOP. Therefore, this paper proposes a fault protection scheme for SS- SNOP, which can quickly detect the fault location, remove the fault and benefit the system recovery. The scheme configuration, short-circuit issues analysis, and implementation are discussed in this paper. Simulation results verify the validity of the proposed protection scheme.