Accurate modeling, compensation and self-commissioning of inverter voltage distortion for high-performance motor drives

Dead-times, power devices voltage drops and total output capacitance represent the most important sources of distortion of the average output voltage in voltage-fed PWM inverters. Their effect is a function of actual parameters of the drive system and of the operating conditions, and is often intolerable in many drives applications, thus requiring a proper compensation strategy. Many techniques are implemented in industrial drives and reported in literature, even very recently. Necessary dead time between the two switches of each leg for sure represents the main cause of distortion and is therefore the most investigated topic in technical literature. Less often the compensation strategy is based on an actual model of the converter due to the increased complexity of the modeling task and consequently due to the difficulties in the compensation approach. The methodology considered in this paper belongs to this last class and is based on a detailed physical model of the power converter. A novel approach is presented to obtain a properly simplified model, thus allowing the derivation of a simple but effective compensation strategy. A novel self-commissioning identification of the compensation model parameters is proposed and its validity and effectiveness is verified on a commercial general purpose drive. Comparison with respect to standard compensation techniques is reported and demonstrates the superior characteristics of the proposal. Finally, dramatic performance improvements of a sensorless drive system are also shown to gain an additional validation of the method.