Research on the relay protection system for a small laboratory-scale microgrid system

As one strategy of power management, microgrid has the special superiorities on not only improving power quality but also relieving the pressure on energy and environment. To carry out experiment and research, a small laboratory-scale microgrid system with energy storage device, single phase and three-phase photovoltaic devices and wind power devices are planned to build. Fault current in the microgrid system is limited by using of the distributed sources equipped by power electronic device. So the traditional relay no longer works. By determining the fault occurrence and fault zone according to bus bar voltage disturbances and power directions, the protection system can play an outstanding role in both grid-connected operation mode and islanded operation mode. The structure and control strategy of the microgrid experimental system and relay protection principle are described in this paper. Also, the relay protection system hardware and software have been designed based on industrial personal computer (IPC). Experimental results have shown that the protection system can operate safely according to requirements.