Sliding mode regulator for maximum power tracking and copper loss minimisation of a doubly fed induction generator

Maximum power tracking and copper loss minimisation of a doubly fed induction generator (DFIG) can be achieved through the control of rotor currents. In this study, a sliding mode regulator (SMR) is presented to regulate the rotor current of a DFIG. The purpose of the SMR is to regulate the rotor current to the target commands of maximum power tracking and copper loss minimisation with stator flux orientation. The robustness to parameter variations can be accomplished by the proposed SMR when the wind turbine is subject to changing wind speed. Simulation results of the DFIG system on a 2.5 MW generator are provided and compared with a fixed-gain proportional-integral (PI) regulator. It is observed from the simulation results that the dynamic responses achieved by the proposed SMR are more robust than those by the fixed-gain PI regulator. The chattering effect caused by the switching function of the SMR can be reduced by an integral type SMR.