Direct torque control strategy applied to the grid connected wind farm based on the PMSG and controlled with variable structure approach

Abstract

This study proposes a direct torque control (DTC) and variable structure (VS) scheme for grid connected variable speed wind farm (VS-WF) based on the permanent magnet synchronous generators (PMSGs). The control strategy combines the DTC to achieve maximum power point tracking (MPPT) and nonlinear sliding mode (SM) control theory to sustain the DC-bus voltage and to regulate the grid-side power factor. Moreover, control strategies are developed in the sense of Lyapunov stability theorem for the VS-WF to satisfy multiple objectives. The performance of controllers is evaluated for fault conditions as well as for normal working conditions. The validity and the effectiveness of the proposed scheme are verified by simulation with Matlab/Simulink. Also, a comparison of simulation results based on the proposed algorithm and proportional-integral (PI) scheme shows that the proposed approach is superior.