Grid connected/solar water pump for rural areas

A novel water pumping system is proposed with a view to implementation in either a mini-grid or a single-wire-earth-return (SWER) scenario. The system utilises a three-phase inverter which can draw power either from a solar energy input or from a single phase AC supply to drive a three-phase induction motor. On the AC side, one phase of the inverter is connected to the supply through an inductor. By changing the phase relationship between the two waveforms, bi-directional power flow results. This front-end rectifier enables the inverter to draw sinusoidal input current at unity power factor while also reducing the switch count. On the DC side, the output power of the solar array is monitored and the system allows the bus voltage to fluctuate within bounds in order to track the optimum power point. Voltage regulation of the output is then achieved through adjusting the modulation index of the PWM control signals. This paper presents initial results from a small-scale test system and discusses the merits of the proposed scheme