A load commutated inverter-fed induction motor drive system using a novel DC-side commutation circuit

A load-commutated current source inverter (LCCSI) induction motor drive system employing a novel DC-side forced commutation circuit for machine start-up is proposed. To avoid the adverse effects of harmonic resonance between the output capacitor and the inductance of the induction motor, a solution is proposed using a special type of one-notch current PWM, fully utilizing the proposed commutation circuit. A direct vector controller, which refers to the fixed reference frame of the rotor flux without using a speed sensor, is applied. In addition to compensating for the capacitive current, this controller is applied to decouple the torque and flux generating currents and to overcome the instability caused by the output capacitor. The feasibility of the proposed circuit for the high power drive system is verified by computer simulation for a 600 hp induction motor. Experimental results for a laboratory LCCSI-induction motor (10 hp) are also included