Proportional-Resonant and Unipolar Switching Control of Single-Stage Solar Photovoltaic Grid Interfaced System

In the proposed work, a new control is used with inner loop as a current control and the outer loop as a voltage control of a solar photovoltaic (PV) array-fed single-phase grid interfaced system, using a voltage-source converter (VSC). It deals with the power quality mitigation, which includes power factor correction, harmonic mitigation in abnormal conditions such as grid voltage sag and swell and irradiation changes. The PI (Proportional-Integral) controller is used as an inner current loop control for reference and sensed DC link voltage balancing and to generate the command for the harmonics accurately, which generates the reference current. The PI controller is used for generating reference current and PR (Proportional-Resonant) is used for generating voltage reference, which, in turn, produces modulating signal within the limit of carrier wave. A comparison between reference voltage and carrier gives unipolar switching, attaining three levels for the VSC. Here, the maximum power point tracking (MPPT) is achieved by an incremental conductance (INC) method. Experimental performance is studied at dynamic abnormal conditions such as voltage sag and voltage swell in order to investigate the total harmonic distortion (THD) of the grid current and point of common coupling (PCC) voltage, which are observed within the IEEE-519 standard.