Encoderless model predictive control of back-to-back converter direct-drive permanent-magnet synchronous generator wind turbine systems

This paper presents encoderless model predictive control scheme with time-varying sliding mode observer for a complete wind turbine system. The wind turbine system consists of a back-to-back converter (AC/DC/AC) and a direct-drive permanent-magnet synchronous generator (PMSG). We give a complete model of the system and present encoderless fixed-frequency model predictive direct torque control of the generator and finite-set model predictive direct power control of active and reactive power on the grid side. The sliding mode observer utilizes a time-varying switching gain and a time-varying cut-off frequency to estimate rotor position and rotor speed without chattering. The proposed strategy is illustrated by simulations as a first proof of concept. The simulation results show that the proposed strategy achieves fast torque control dynamics and highly decoupled control of active and reactive power.