Voltage Control in an Autonomous DFIG-DC based Wind Energy System

This paper proposes a control technique for an autonomous DFIG-DC wind energy generation system. In autonomous DFIG-DC wind energy generation system, the stator and the rotor are connected to a dc load or micro-grid by a diode bridge rectifier and a controller power electronics converter respectively. DC voltage regulation is visibly necessary for stand-alone operation and DC micro-grid connected operation. The stator frequency and the DC side voltage regulation are achieved by an indirect control scheme, where maintaining constant DC voltage and frequency through a controller which is designed in polar coordinate frame rotating at slip frequency. Compared to other conventional techniques such as field-oriented control, the presented control technique is very simple and easy to implement. The hysteresis current controller provides the control pulses for rotor side controlled power electronics converter by the actuated by the error signal calculated between actual and reference rotor currents. The reference rotor currents are calculated by the presented indirect control scheme. The autonomous DFIG-DC wind energy generation system is designed MATLab and Simulink software platform. The performances of the system are verified by the simulations of different possible cases.