SPV-BES System Synchronized to Three-Phase Four-Wire AC Distribution Network

Solar photovoltaic (SPV) system performance degrades due to the presence of nonlinear/unbalanced loads at the point of common coupling (PCC). These loads also cause the current in the ac network's neutral conductor, which causes additional losses and the voltage difference between the neutral conductor and the ground. This work addresses these problems and presents the control algorithm for the SPV system to improve its performance and the power quality (PQ) at the PCC, to reduce the current flow in the ac network's neutral conductor, and to maintain the balanced operation in the ac network at unbalanced loads. The battery energy storage is incorporated with the SPV system to improve the supply's reliability at the load end by operating the system in the islanded mode (ILM) when the ac network supply is interrupted. A new application of the variable zero attracting (VZA) least mean square (LMS) adaptive control algorithm is presented for the PQ improvement in both grid-connected mode (GCM) and ILM operations. The VZA component reduces the steady-state oscillation in the LMS algorithm without compromising its dynamic response. The seamless operation is used to avoid any abnormality in voltages and currents of the system operating mode changes from the ILM to the GCM after the grid recovery. The performance of the system is tested on the developed Simulation model and further verified by the experimental study performed on a reduced rating prototype.