This paper describes the output voltage regulation for the islanded mode of microgrid based on inverter with LCL filter. When a microgrid is transferred to the islanded mode, it has to supply the full local load demand without supporting of grid and to operate as a voltage source with an appropriate voltage regulation. Here, if the local loads are unbalanced and nonlinear, then it makes the output voltage distorted and so the performance of power quality will be degraded. In this paper, P+ multiple resonant controller which makes the control gain very high on the specific frequency range has been selected instead of PI controller for the compensation of voltage distortion due to the unbalanced and nonlinear load. The effect of voltage regulation method using P+ multiple resonant controller under the nonlinear and unbalanced condition has been verified through the PSIM simulation results. And then it also has been compared with the conventional PI and the advanced PI for harmonic compensation.
