Brush-DC equivalent control based delta modulation for a PWM inverter-fed nine phase induction machine drive

A recently developed control method for multiphase induction machine drives termed the Brush-DC Equivalent control has presented a simpler control strategy that does not use any complex transformations. It has been implemented using a hysteresis current controller and in this paper, a delta modulated current control technique is presented. Delta modulation is proposed in to replace hysteresis control because hysteresis control uses a varying switching frequency which makes harmonic filtering and protection of the inverter difficult. A constant switching delta modulation scheme eliminates these challenges. It has inherent harmonic filtering giving better performance in terms of current and torque ripples. A Brush-DC controlled nine-phase cage rotor induction machine drive is used to investigate the implementation of the delta modulated current controller. The drive is simulated using Matlab/Simulink to determine its performance when stator voltages are used as feedback to the filter in the delta modulator.