Investigations into the performance of photovoltaics-based active filter configurations and their control schemes under uniform and non-uniform radiation conditions

With their growing popularity as alternative to conventional fuel, photovoltaics(PV) are being increasingly employed for a wide range of applications. Power quality improvement through a PV-fed active filter (PVAF) or inverter is one such application. A PVAF can supply active and reactive power to the grid when solar radiation is available or control the reactive power during periods of low or no radiation. The advantages of PVAF as an independent active source of compensation, reduced transmission losses etc. over a conventional AF have already been highlighted in the literature. However, not much attention has been paid to the effects of the PVAF configuration on its operational performance. Similarly, the effect of control schemes used to control such filters has also not been investigated. Various configurations of PVAF (viz. string- or multiple-string- or centralised-inverter based) are possible depending upon the configuration of the PV array (source). This study compares various PVAF configurations and their control schemes in terms of their ability to compensate reactive power, harmonics and phase-imbalances caused by unbalanced linear and non-linear loads in a three-phase, four-wire distribution system. Performance parameters such as power output and power quality as described by total harmonic distortion, phase imbalance and neutral conductor current are evaluated under both uniform and non-uniform radiation (e.g. partially shaded) conditions. In particular, results are presented to highlight and compare the effects of partial shading on the control schemes and PVAF configurations. Based on this study, several critical observations and remarks are presented.