A current-source-inverter-fed induction motor drive system with reduced losses

Standard low- and medium-power induction motor drives are based on the pulsewidth modulation (PWM) voltage-source inverter fed from a diode rectifier. The dual topology, based on the current-source inverter/rectifier structure is used in medium- and high-power applications. This paper analyzes the existing motor drives based on current-source topologies and proposes a control strategy that addresses some of the drawbacks of this approach compared to the voltage-source approach. The proposed strategy features the following: I) an on-line operated PWM inverter, using instantaneous output capacitor voltage control based on space-vector modulation and 2) an additional inverter modulation index control loop, ensuring constant inverter modulation index and minimum dc-link current operation. The resulting additional advantages include the following: 1) fixed and reduced motor voltage distortion; 2) minimized de-bus inductor losses; 3) minimized switch conduction losses; and 4) elimination of motor circuit resonances. Experimental results based on a digital signal processor implementation are given.