Predictive phase locked loop for sensorless control of PMSG based variable-speed wind turbines

Abstract

In this work, a new predictive phase-locked loop (PLL) for encoderless control of a permanent-magnet synchronous generator (PMSG) in a variable-speed wind energy conversion system (WECS) is presented. The idea of the predictive PLL is derived from the direct-model predictive control (DMPC) principle. The predictive PLL uses a limited (discretized) number of rotor-angles for predicting/estimating the back-electromotive-force (BEMF) of the PMSG. subsequently, that predicted angle, which optimizes a pre-defined quality function, is chosen to become the best rotor-angle/position. Accordingly, the fixed gain proportional integral (FGPI) regulator that is normally used in PLLs is eliminated. The performance of the predictive PLL is validated experimentally and compared with that of the traditional one under various operating scenarios and under variations of the PMSG parameters.