Investigation of Limitations in Passive Voltage Clamping-Based Solid-State DC Circuit Breakers

Abstract

This paper investigates limitations of passive voltage clamping based dc solid-state circuit breakers (SSCBs). There are two major contributions of this paper. First, it presents a unique quantifying study of limitations in metal oxide varistor (MOV) clamping based SSCBs in terms of gate voltage distortions and power shock. Second, it provides a comprehensive quantifying investigation of limitations in MOV and resistor-capacitor-diode (MOV-RCD) clamping based SSCBs regarding the power shock and response speed. For MOV based SSCBs, both gate voltage distortions and power shock during turn-off are extremely high, causing switch degradation/failure. For MOV-RCD clamping based SSCBs, a snubber capacitor is added to reduce dv/dt and power shock. However, this capacitor brings two main limitations: a) inevitable high transient power/energy shock at high-current interruption and b) low turn-off speed caused by high-inertia capacitor charging at low-current interruption. Two prototypes are implemented to illustrate limitations: a discrete SiC MOSFET-based 500 V/20 A SSCB, and a SiC MOSFET module-based 800V/100A SSCB. Experiments validate that the transient power shock can reach 256 kW at a 1.2 kA fault current interruption, which affects system reliability. Moreover, the response speed at a 100 A case (7.8 μs) can be 14 times slower than the 1 kA case (0.56 μs) due to the snubber capacitor charging process, which leads to inconsistent control and coordination of SSCBs.

Keywords

• MOV
• power and energy shock
• RCD snubber
• SSCB