Development of Adaptive Hysteresis-band Current Control of PWM Three-Phase AC Chopper with Constant Switching Frequency

Three-phase AC choppers are widely used to obtain a variable alternative voltage from a fixed alternative source for the control of alternative motors at variable speeds. The hysteresis current control is one of the simplest techniques used to control the magnitude and phase angle of three-phase motor currents for high-speed drive systems, primarily because of its implementation simplicity, fast current control response, and inherent peak current limiting capability. However, conventional fixed hysteresis-band current control has a variable switching frequency throughout the fundamental period, and consequently, the load current harmonic ripple is not optimum. In this article, a simple, novel adaptive hysteresis-band current control technique is proposed, where the hysteresis band is controlled as variation of input voltage, output voltage, and slope of the current error to achieve constant switching frequency at any operating condition. The high performances of this novel technique are verified by digital simulation.