A two-stage converter based controller for a stand alone wind energy system used for remote applications

This paper proposes a control strategy for tracking and maintaining a constant voltage and frequency across remote loads through stand alone variable speed wind energy conversion system (VSWECS). The system consists of a variable speed wind turbine coupled to a permanent magnet synchronous generator (PMSG). Output of the PMSG is first converted into a fixed DC voltage using a buck chopper. The control of the chopper is achieved by varying the duty ratio of the gating pulses of the power electronic switches. The dc output from the chopper is then inverted to obtain the ac supply using a pulse width modulated (PWM) inverter. The control of the inverter is achieved by changing the modulation index of the PWM. Both the dc output voltage of the chopper and AC output voltage of the inverter are controlled through the proposed controllers that follows the common control law. The proposed wind energy scheme has been simulated and analyzed in the MATLAB/SIMULINK platform for different wind speeds and load variations. The scheme is also designed with power alternatives so as to ensure the uninterrupted operation to overcome the problem of very low wind speeds.