Performance comparison of wind turbine based doubly fed induction generator system using fault tolerant fractional and integer order controllers

A typical grid connected wind energy system is always associated with the nonlinear dynamics, uncertainties and external disturbances. Moreover as per the adopted grid codes and in the occurrence of specific faults the wind energy system should remain connected to the grid for a defined time period. Keeping in view all the effects this article proposes a high performance fault tolerant fractional order control system for the rotor side converter of a doubly fed induction generator (DFIG). The base line controller is formulated using novel fractional order sliding manifolds and the stability of the closed loop is ensured using fractional order Lyapunov theorem. As a case study the faults are introduced in the rotor current sensors and a model based fault tolerant rotor current estimation algorithm is proposed which is based on the stator measured currents and the voltages. Numerical results are presented to show the superiority of the proposed base line fractional order control method over the classical sliding mode control system in normal operating conditions. Finally the proposed algorithm is tested under the rotor current sensors fault and the results under faulty conditions are compared to that without faults. (C) 2017 Elsevier Ltd. All rights reserved.