Fault-Ride Through Strategy for Islanded Microgrids Via Dynamically Reconfigurable Voltage Reference

In an islanded microgrid, the inverter interfaced distributed generators (IIDG) can easily burn out when short circuit faults occur. Also, the system voltage/frequency may suffer from large deviations due to the small system capacity and the absence of utility grid support. This paper proposes a fault-ride through (FRT) strategy for islanded microgrids via the dynamically reconfigurable voltage reference unit (DVRU). All the IIDGs will switch from the voltage control (VC) mode to the adaptive current control (ACC) mode coordinately when a fault occurs, and re-switch to the VC mode after the fault is cleared. The entire FRT process is guided by the DVRU. The local fault current differential time delay method (FCDDM) is also proposed to realize the automatic selection of DVRU. Moreover, when the present DVRU undergoes communication failure, a new DVRU will quickly replace the former one. Therefore, a reliable FRT control can be achieved to guarantee all the IIDGs' safety and system stability. Finally, experimental results demonstrate the effectiveness of the proposed strategy both under short circuit faults and communication failure.