Two management strategies to deal with PWM inverter´s control variable saturation

Two strategies dealing with successive and simultaneous limitations of PWM (pulse width modulation) inverter control variables are presented. The simple coordinated limitations strategy allows the use of the whole DC supply voltage without current distortions independently of the current controller tuning. In this case, the controller outputs directly represent the PM synchronous machine terminal voltages. This way, the linear torque range is increased by a rate of 15%. The second limitation strategy, dedicated to dealing with simultaneous limitations, is much more difficult to implement and barely reduces the torque ripples in comparison with the first limitation strategy. This second method attempts to maintain a set of balanced voltages at the machine terminals to reduce the torque ripples in case of double limitations