Voltage unbalance compensation using novel virtual impedance loop

Abstract

In microgrids Voltage Source Inverters are generally used for integration of distributed energy generation resources to supply the load demand. Microgrids have the capability to meet the power demand of local loads even if the main grid fails. Under this condition voltage and frequency support from the main grid is not available, so it is the responsibility of VSIs to keep voltage and frequency of the microgrid within limits. Loads such as three phase unbalance load, single phase high impedance faults, or nonlinear loads (rectifier, ASD, VFD etc) may cause severe voltage unbalance and harmonic distortion. Voltage unbalance in an islanded microgrid is mitigated by implementing a novel virtual impedance loop. The proposed control strategy is based on Synchronous Reference Frame (SRF) theory. The proposed microgrid is simulated in MATLAB/Simulink SimPower System tool box.