Harmonic current reduction for a PWM rectifier with very low carrier ratio in a microturbine system

When a PWM rectifier is connected to the generator in a microturbine power generation system to form a "back-to-back" configuration together with a grid-connected PWM inverter, the rectifier will have to operate with a very low PWM carrier ratio, since the generator output frequency can be as high as of kHz level while the switching frequency of semiconductors are limited. A method to reduce the distortion of the generator side currents in such a case is proposed, featuring a carrier factor of 5; a modified SPWM scheme to eliminate the 3^rd order harmonic and its multiples from the current spectrum; and an LC-resonance based notch filter to remove the remaining most significant harmonic component. Simulation results show that near perfect sinusoidal generator current can be obtained with this method