PWM control methods suitable for high speed induction motor drives

Abstract

New control methods are described which can suppress instability generated at high frequencies when an induction motor is driven by a PWM inverter. The methods are discussed according to two categories of motor driving system: using closed loop control with current regulators; and using open-loop control with only PWM controllers. The former prevents instability of the primary currents from occurring at high frequencies by controlling the amplitude and the frequency of the carrier wave. The latter prevents oscillations of primary currents from occurring at high frequencies by generating PWM signals while controlling the sampling time of the space vector control so that the ratio of 2π to the instantaneous phase of the primary magnetic flux reference can be kept integer. Experiments confirm that both methods enable induction motors to be smoothly driven up to high frequencies such as 500Hz.