Optimal RSC Control for Loss Reduction in Wind Turbine Driven DFIG-Grid System

This work presents an optimal control for RSC (Rotor Side Converter) of a wind turbine driven doubly fed induction generator (DFIG) interfaced to the three-phase grid. The RSC control is designed to minimize the total losses of the DFIG, which is a combination of stator and rotor copper losses. The total loss reduction is achieved at every wind speed by supplying the reactive power of DFIG both from RSC and grid side converter (GSC). The analysis is carried out on a 3.7 kW DFIG to determine the optimal reactive power sharing by the RSC at each wind speed. Moreover, the variations of stator, rotor and total losses with respect to reactive power sharing from RSC, are presented at all wind speeds between the minimum and maximum speed regions of DFIG. The optimal control gains are obtained within the maximum power point tracking (MPPT) region of the wind turbine generator. The control performance is validated by developing a prototype in the laboratory. Moreover, test results are presented when the DFIG is operating at below synchronous speed, during the transition from below to above synchronous speeds, under wide varying wind speeds, and at load change.