Sensorless Model Predictive Direct Current Control Using Novel Second-Order PLL Observer for PMSM Drive Systems

The model predictive direct current control (MPDCC) is a promising control approach for high- power converters. It takes the discrete states of the voltage source inverter (VSI) into account, and the future converter behavior is predicted for each sampling period. Possible voltage vectors are selected by a graph algorithm, and the most appropriate one is chosen based on an optimization criterion in order to obtain high dynamics. Applying this method to sensorless MPDCC drive systems, special observer characteristics are required. For this reason, an angle and speed observer has been designed. The position of the internal voltage vector, i.e., the back electromotive force, is obtained with a phase-locked loop structure. Control strategy and observer have been developed for permanent-magnet synchronous machine drive systems, and they have been implemented on a small-scale system with two-level VSI for demonstration. This new observer has the advantages to combine high bandwidth with disturbance robustness and can be applied to round rotor and salient pole machines. Moreover, the possibility to combine MPDCC with a sensorless observer is shown.