An improved sequential hysteresis current controller for three-phase inverter: design and hardware implementation

This paper presents a multivariable hysteresis current controller for three-phase inverters. Current control is very important in variable speed drives for induction and permanent magnet motors. The sequential design for the multivariable controller combined with a time delay zone creates a second hysteresis band that contributes to reduce transistors switching frequency and to estimate the disturbance in order to apply the most suitable voltage vector. An analysis on possible disturbance directions and simulations results achieves the design of an improved sequential machine that further decrease the switching frequency. The design of the experimental setup, problems related to the disturbances on current sensors and the necessary modifications on the sampling time are described. The performance of the improved sequential controller is tested on an induction motor.