MPPT control algorithm for grid integration of variable speed wind energy conversion system

In this paper, a 1.5 kW interior permanent magnet synchronous generator (IPMSG) with a power conditioner for grid integration of a variable-speed wind turbine is developed. The power-conditioning system consists of a series-type 12-pulse diode rectifier powered by a phase shifting transformer and then cascaded to a PWM voltage source inverter. The PWM inverter is utilized to supply sinusoidal currents to the utility line by controlling the active and reactive current components in the q-d rotating reference frame. While the q-axis active current of the PWM inverter is regulated to follow the optimized active current reference so as to track the maximum power of the wind turbine, the d-axis reactive current can be adjusted so as to control the power factor. In order to track the maximum power of the wind turbine, the optimal active current reference is determined by using a simple MPPT algorithm which requires only three sensors. Moreover, the phase angle of the utility voltage is detected using a simple electronic circuit consisting of both a zero-crossing voltage detecting circuit and a counter circuit employed with a crystal oscillator. The laboratory results indicate that the proposed scheme provides a viable solution for the grid integration of the variable-speed wind turbine using a cost-effective, high efficiency power conditioner.