Optimizing the Performance of Single-Phase Photovoltaic Inverter using Wavelet-Fuzzy Controller

During grid-connected operation, photovoltaic (PV) systems are usually operated to inject pre-set power to the grid. However, when the main grid is cut off from the PV system, standalone operation must be achieved while operating in voltage control mode. This brings new challenges for the control of PV inverters, i.e., voltage regulation and harmonic elimination. In this research, a wavelet-based fuzzy control for standalone operation of single-phase inverters is designed. The proposed controller regulates the output voltage by adjusting the fuzzy controller weights, which are operating in closed loop with the pulse width modulation generator. A hardware prototype of 1kWp standalone PV system is developed, and the proposed control method is evaluated on it. The proposed control achieves <6% of output voltage regulation under steady state and step load conditions while reducing total harmonic distortion (THD) for steady state condition. The THD of the proposed system operating with linear loads is observed to be 2.18%, and for nonlinear loads, it is around 2.71% under simulation conditions.