A stand-alone wind energy system with battery storage

Abstract

A stand-alone power supply system based on wind energy is presented in this paper. A permanent magnet synchronous generator (PMSG) is connected to the load through a switched mode rectifier and an inverter. Battery is used as an energy storage device and interfaced to the wind energy system through DC-DC converter. Control strategies are presented to regulate voltage and frequency of a stand-alone system. By controlling dc-link voltage at its reference value, the output ac voltage of an inverter can be maintained constant irrespective of variations in the wind speed and load. An algorithm is developed to achieve energy management among the wind generator, battery and dump load. The proposed energy management algorithm is simple and requires measurement of only dc link voltage. The effect of unbalanced load on the generator is analysed and a control technique is developed to reduce its effect on the mechanical torque of the generator. Moreover, PWM inverter control is incorporated to balance the line voltages at point of common coupling (PCC) under the condition of load unbalance. Simulation results show that the controllers can regulate the PCC voltage under the condition of fluctuating wind speed, varying load conditions and under unbalanced load condition.