An Improved Quadratic V/f-Based Control of Photovoltaic Battery-Less Induction Motor Driven Water Pumping System

This paper proposes a new quadratic V/f-based control of a PV induction motor driven water pumping system without storage batteries. The system consists of PV array, DC-DC boost converter, voltage source inverter (VSI), induction motor, and water pump. In order to extract the maximum power from the PV array, the incremental conductance (INC) method is simply utilized. The dc-link voltage is maintained constant using a proportional-integral (PI) controller by controlling the induction motor speed using simple open loop quadratic scalar V/f control. The proposed quadratic scalar V/f control is compared with the widely used linear V/f control using a simulation case study based on MATLAB/SIMULINK . The performance of the proposed method is examined under variable values of solar radiation. When compared with the available scalar controllers, the proposed controller generally improves the system dynamics as well as the overall system efficiency especially under low speed (low discharge) operation. The simulation results have proved that the system output power and the corresponding overall efficiency have been approximately doubled under low speed operation.