Switching Motion Control of Piezoelectric Actuators in Hybrid Circuit Breakers for MVDC System Protection

This paper presents a switching motion controller for a piezoelectric actuator used in fast mechanical switches, which are the essential parts in hybrid circuit breakers for protecting medium-voltage direct-current power systems. The proposed control strategy has improved switching operations of a prestressed piezoelectric stack actuator carrying a heavy load to reach a large displacement within one millisecond. A notch filter is used in the proposed controller to attenuate subsequent vibrations in travel curves that may cause switching delays and insulation failures in the fast mechanical switch. With optimized switching operations of the piezoelectric actuator in a fast mechanical switch, the overall hybrid circuit breaker can respond to short-circuit currents more rapidly and reliably, and the overall direct-current system can be better protected.