Coordinate Control of Power and Current Quality for Grid-connected PV Inverters Under Unbalanced Grid Voltage

Power oscillation and current quality are the important performance Index for the photovoltaic(PV) grid-connected inverter under unbalanced grid voltage. Firstly, the generation mechanism of the current harmonic and power oscillation of the PV grid-connected inverter is discussed with a quantitative analysis. Secondly, a new stationary frame control strategy is proposed. The current reference is directly generated with the instantaneous power concept, which greatly simplifies the control structure due to no need of the phase-locked loop and voltage/current positive/negative sequence extraction calculation. The coordinate control of power and current quality is achieved with the weighted idea, which enhances the operation performance of the PV grid- connected inverter. Finally, the simulation and experiments are carried out under the unbalanced grid voltage. Results verify the feasibility and effectiveness of the propose method.