Stand alone photovoltaic system with integrated online UPS to smooth output fluctuations

Abstract

Photovoltaic (PV) systems have considerable output voltage fluctuations due to weather condition, day time, and PV cell partial shading. Hence, standalone PV systems are generally connected to their loads through a suitable power electronic interface. In other hand, an on-line Uninterruptible Power Supply (UPS) is capable of providing continuous power delivering without any voltage fluctuations. Therefore, employing a PV system with a UPS can overcome the inherent shortcomings of the PV system. In this paper, a PV system with an integrated three-phase on-line UPS is proposed. An efficient isolated structure for the battery charger of the system is suggested. The PV cells, energy storage device, and critical load have galvanic isolation from each other in the system. In order to diminish voltage fluctuations on load side a developed dual feedback control approach is presented. The isolation decreases stress on the battery and improve UPS flexibility. The operation of this topology and the relevant developed control strategy were discussed in detail. Performance of the system is verified and approved using some simulations in MATLAB/Simulink.