Control Strategy of a Wind Turbine Drive by an Integrated Model

In this paper, an integrated equivalent circuit is defined to analyse the operation of a wind generator-rectifier system connected to a DC link, with the electric machine consisting of a surface-mounted permanent magnet synchronous generator (SPMG) directly coupled to the wind turbine. Such circuit is defined by integrating the models related to the electromechanical equations implemented into a Simulink (R) code, where the SPMG parameters are derived by the elaboration of sequences of magnetostatic FEM analyses. The integrated equivalent circuit can be very useful to examine the wind generator dynamics because of wind speed variations, and to analyse the influence of the electromechanical parameters on the energy output in order to identify the appropriate control strategies involving the regulation of the rotor speed, the DC link current and the blade pitch angle. In particular, a sensorless algorithm is implemented to estimate the main mechanical quantities (output torque and rotor speed) and to determine the wind speed by means of only electrical measurements. The comparison with an anemometer-based solution shows that similar performances can be achieved in different operating conditions. The control strategies set up by the circuit model are verified on a 20 kW-rated SPMG with outer rotor, comparing the sensor and sensorless approaches in terms of capability of energy production, dynamic promptness and sensitivity to parameter disturbances, also with wind turbulence.