Improving Switching Frequency Variation of Hysteresis Current Controlled VSI Fed Induction Motor Drive

Abstract

Switching frequency variation over the entire operating speed range of an induction motor (IM) drive is the major problem associated with conventional two-level threephase hysteresis controller as well as the space phasor based pulse width modulation (PWM) hysteresis controller. This paper presents a new variable band hysteresis current controller for controlling the switching frequency variation in the two-level PWM inverter fed IM drives for various operating speeds. A novel concept of online variation of the band based on both the instantaneous load current and current change for eachsampling period is presented to determine the hysteresis band. A performance comparison of the proposed with conventional hysteresis current controller for IMdrive is provided in simulation. The proposed drive system is also implemented in real-time using DSP board DS1104 for a laboratory 1.5 hp motor. Comparative simulation andreal-time results verify the feasibility of the proposed scheme and demonstrate that the proposed method has obtained constant switching frequency and improved the performance of the drive system.