Investigate dynamic and transient characteristics for islanded/grid-connected operation modes of microgrid and develop a Fast-Scalable-Adaptable fault protection algorithm

Development of a microgrid (MG) system brings some emerging challenges. One of them is the fault protection system. In order to develop an optimal fault protection algorithm, this paper surveys dynamic and transient behaviours with respect to two operation modes of a microgrid, namely, islanded and grid-connected modes. Modelling and simulation of the MG´s operation are performed by the PSCAD/EMTDC software. A surveyed typical MG structure includes a dispatchable power source of microturbine (μT) system, another non-dispatchable source of photovoltaic (PV) generation system and a battery power conditioning system (PCS). Whereas dynamic characteristics of the MG are investigated in cases of power change of loads or sources and motor starting, transient properties are surveyed through staged fault tests such as: single-phase and three-phase to ground faults and the MG´s operation transition between grid-connected and islanded modes. Simulation results are compared to actual experiment results performed at a 380V microgrid at Institute of Nuclear Energy Research (INER), Taiwan. From achieved dynamic and transient properties, this paper proposes a Fast-Scalable-Adaptable (FSA) fault protection algorithm to improve the MG´s reliability and adaptability operation. This new algorithm uses parameters of current, voltage and phase angle along with the communication network to protect online the microgrid. The proposed algorithm can solve challenging problems of high penetration of inverter-based distributed generators (DGs), reduced fault current values and nondirectional power flow. Moreover, the algorithm can get a fast fault clearing time below one fault cycle, optimal detection and identification of different fault types and exact isolation of faulted zones. Simulation and experiment results validate the proposed FSA fault protection algorithm.