Broadly speaking, the choice of lower stator voltage depends on the new maximum slip under consideration. Since most transformers have the provision of tappings, such a voltage switch-over does not warrant any design modifications or additional cost. Further, since the speed is a slowly changing variable, a speed sensor along with a contactor based voltage switching is adequate for real time implementation. The scheme is simple and economical in implementing and yields greater annual returns through increased LAQ 824 harvesting.
The proposed scheme is verified through MATLAB simulations on a 250 kW wind turbine and also through simulations and experiments on a 2.3 kW laboratory test bench using Altera cyclone II FPGA controller. Results demonstrate the feasibility of moderately efficient extended speed operation with the limited rating converters.
This paper is glucocorticoids organized as follows. Detailed mathematical modeling of a doubly fed induction machine including iron losses is described in section 2. Further the decoupled control of DFIG with RSC and GSC are explained in section 2. Maximum Power Point Tracking from the wind is explained in section 3. Section 4 describes the proposed scheme of extended low speed operation of DFIG. In the first case study, the simulation results of a 250 kW wind driven DFIG are presented and in the second case, the simulation and test results for a 2.3 kW laboratory DFIG are illustrated in section 5.