Harmonic voltage compensation control strategy for droop-controlled inverter in islanded/grid-connected mode

Nonlinear loads connected to the microgrid distort the voltage of the Point of Common Coupling (PCC) and the grid current. Therefore, A droop control based harmonic voltage compensation strategy of voltage controlled inverter in islanded/grid-connected mode is proposed in this paper. To compensate the PCC voltage distortion, fundamental and harmonic voltage components are controlled separately in the voltage loop control. On the synchronous reference frame, the fundamental component is direct flow controlled by proportionintegral (PI) controllers and the harmonic component is alternate flow controlled by proportion-multi resonant (P+MR) controllers. The output of PI controllers and P+MR controllers are added as current reference for the inner current loop control. The magnitude-frequency characteristics analysis of d-axis control loop based transfer function shows that the fundamental and 5
^th
, 7
^th
, 11
^th
, 13
^th
harmonic components can be tracked without error by PI and P+MR controllers respectively. The simulation results in Matlab/Simulink verify that the PCC voltage is compensated effectively by the proposed method in islanded/gird-connected mode.