Performance analysis of directly coupled photovoltaic electro-mechanical systems

Abstract

The application of stand-alone directly coupled photovoltaic (PV) electro-mechanical systems for water pumping has been the increase in remote rural areas of developing countries. The performance of directly coupled PV electro-mechanical systems has here been analysed for DC motors (that is, permanent magnet, series, and shunt motor) coupled to centrifugal and constant loads. It has been observed that for a good match between the characteristics of the PV array and the electro-mechanical system, the load should have torque-speed characteristics that increase as rapidly as possible in the operating region. The analysis has been carried out at different solar intensities with corresponding solar cell temperatures. It has been observed that the operating characteristics of the DC permanent magnet motor coupled with a centrifugal load are best situated relative to the maximum power point locus of a PV array, indicating the quality of matching between the system components. It operates most of the day time and because of its higher starting torque even at low solar intensities as compared with the DC shunt and series motors. The DC series motor coupled with a centrifugal load operates better compared to the DC shunt motor, but operates poorer than the DC permanent magnet motor.