PWM-CSI inverter for induction motor drives

A number of issues involved in designing a current source inverter system for a large induction motor drive are discussed. Using two modulation techniques-selective harmonic elimination in the upper frequency range and trapezoidal modulation in the lower frequency range-control of voltage, current, and torque harmonics is achieved while limiting the gate turn-off switching frequency to 180 Hz. Each modulation range is divided into a number of subranges to exploit the available switching capacity and to avoid harmonic resonances involving the capacitor and the motor inductance. In addition to basic principles, simulation waveforms and test results are included from a laboratory experimental system.<>