Hardware-in-the-loop simulation for testing low voltage circuit breakers selectivity

This paper presents a real time hardware-in-the-loop setup for validation of protection coordination schemes among low voltage protection devices. It employs an embedded controller that combines the advantages of microprocessor and FPGA technology. Simulations are based on the real time model of a small-scale power distribution system, which is a realistic application of low voltage circuit breakers. Because it has to simulate fault currents on the scale of some milliseconds, the HIL system has strict real-time requirements. At the same time, a modular architecture and a user-friendly interface were needed. Final design structure is based on two levels: an embedded controller for real-time signal generation and a computer-based human-machine interface.