Studies on sensor-less hysteretic multi-scalar control of doubly fed machine for wind power generators

As one of the advanced technologies, the variable speed constant frequency doubly-fed induction generator (VSCF-DFIG) has been widely used nowadays. The multi-scalar control scheme of DFIG is firstly introduced in this paper, the current hysteresis PWM technology is then introduced to simplify the control system. An open-loop speed observer is designed according to the multi-scalar control system. By using the rotor current reference components instead of the real current components, the observer design is simplified and observes effect is evidently improved. The dynamic respond performance is better in multi-scalar control system and the whole control process does not depend on any electric machine parameters. The proposed speed observer can overcome some of the disadvantages of the traditional open-loop speed observers. PSCAD/EMTDC simulation software is used to test the proposed scheme. Testing results have demonstrated the efficiency of the control scheme as well as the speed observer.