Speed Sensorless Model Predictive Control for Load Commutated Inverter-Fed Electrically Excited Synchronous Motor

Load commutated inverter (LCI)-fed electrically excited synchronous motor control system is widely used in medium and high voltage industrial applications. In response to disturbances and load change, the system dynamic response performance is poor due to its large inertia coefficient and low switching frequency. A speed sensor less model predictive control method based on LCI-fed electrically excited synchronous motor is proposed in this paper. Firstly, the prediction equation of state is established according to the LCI model, and the appropriate cost function and constraint conditions are given. Then, the control vector model in load commutation mode is analyzed. The design method and parameter selection principle of designed speed observer are given, and the effect of load change on speed observation is analyzed and compensated. At the same time, the designed observer can observe the inverter input voltage and terminal voltage phase. Finally, the proposed speed sensor less model predictive control methodis verified ata 3.75kW LCI-fed electrically excited synchronous motor experimental platform. The results show that the proposed control method can effectively improve the dynamic response performance of system, and the designed observer is feasible. The speed observation error is less than 13°with rated step load.