Seven Level Packed-U Cell based Standalone PV System for Water Pump Application

This article presents a solar-inverter utilizing a seven-level packed U-cell (PUC), with single DC source and two floating capacitors in its topology. The capacitor voltage is balanced in open-loop by implementing multicarrier pulse width modulation (MCPWM) technique. Furthermore, water pumping system is realized with a single phase induction motor (IM)of 1.4KW rating. Stable operation of the said motor is established by integrating close-loop V/f strategy with modulation technique of solar inverter. For this work solar panels of 1.6KW are incorporated to design the PV system. Maintaining optimum performance of any solar powered drive is a major challenge due to unpredictable nature of environmental conditions that effects the power generation capability of PV panels extensively. To address this issue a topology combining battery pack as well as solar panel is proposed as a single DC source of the packed-U cell. This increases the overall reliability of the system. The battery pack is integrated with the solar inverter through a bidirectional DC/DC converter to enable its charging as well as discharging depending on the available power output of the photo-voltaic (PV) arrays. The PV panels are connected with the DC link capacitor of the battery unit through a unidirectional DC-DC converter. A maximum power point tracking (MPPT) strategy is implemented to enable maximum power extraction from these panels.