Permanent-magnet wind turbines control tuning and torque estimation improvements

This paper presents and discuses different PI tuning methods and control strategies for a permanent magnet synchronous machine. The machine is a part of a wind turbine generation system in which two back-to-back-connected three-level converters are the power interface to the electrical grid. It is demonstrated that, for the speed control loop, the zero-pole cancellation method does not provide good performance to the system. Therefore, the PI regulator should be tuned using other strategies. Furthermore, a torque estimator is included in the speed control loop which practically avoids any transient process due to wind torque disturbances. The results are experimentally verified in a laboratory prototype.