Maximum power transfer to solar powered water pumping system using differential compound DC motor

Photovoltaic. (PV)-powered water pumps have received considerable attention because of major developments in the field of solar-cell materials and power electronic systems technology. There are various types of motors available for the PV water pumping applications: dc motors and ac motors. DC motors are preferred where direct coupling to photovoltaic panels is desired, whereas AC motors are coupled to the solar panels through inverters. In solar powered PV pumps as input solar energy is freely available so it is desired that total water to be pumped out over the day, is to be maximized. Objective of the proposed system is to maximize the speed of pump and DC motor for a particular insolation (G) and temperature (T), in order to maximize the water to be pumped out. Field current speed control method is simulated here to optimize the speed of the DC motor at any value of insolation(G) and temperature (T). The dc-dc converter can be used to keep the PV-panel output voltage constant and to help in operating the solar arrays close to the maximum-power point. The variable field current control is also compared with fixed field current method and then differential compound DC motor driven centrifugal pump-set.