Optimal power extraction control schemes for five-phase PMSG based wind generation systems

Abstract

This paper presents a variable speed -wind energy conversion system (VS-WECS) based on a large-scale grid-connected five-phase permanent magnet synchronous generator (PMSG). This work studies control techniques for five-phase PMSG, where back-to-back converters (BTBC) are employed on the machine and the grid side converters. Two control loops are employed to control the machine side converter (MSC) in order to attain the optimum power at any wind speed. The outer control loop is applied to adjust the rotor speed while the inner control loop is employed to regulate the generator current. On the other hand, the grid side converter (GSC) employs two control loops; the outer loop controls the DC-link voltage while the inner one regulates the grid current. Moreover, the maximum power point tracking (MPPT) and pitch angle control schemes are utilized to obtain the optimal power during different environmental conditions. The proposed integral sliding mode controller (ISMC) is employed to regulate the rotor speed of the five-phase PMSG to track the reference speed at different wind speed. The proposed ISMC considers the limitations of the conventional PI controller and the dynamic system disturbance, especially in the large wind turbine inertia. Furthermore, the proposed ISMC stability is examined using Lyapunov’s stability function. The performance of the proposed ISMC is compared to a conventional PI controller, the study shows the superior performance of the ISMC. The overall WECS efficiency is improved using the proposed ISMC to 92.45% compared to the PI controller which is 88.12%. The effectiveness of the proposed control scheme is carried out through simulation results using MATLAB/SIMULINK.