Study Of Doubly Fed Induction Machines Regulation System Based On Direct Torque Control

The doubly fed induction machines speed adjustment system has the advantage of good speed adjusting behavior, low harmonic pollution, high reliability and cheap productive price. Due to these characteristics, it is especially suitable for those situations with high voltage level, high power and not large speed adjustment range, such as wind machines and pump load. In addition it can be used in the situations of generating electricity by wind power and tide. So it is very important to study the doubly fed induction machines speed adjustment. Direct Torque Control (DTC) which was developed rapidly in the middle of 1980's has been applied to many occasions up to now. It will be very important to apply the idea of DTC to the doubly fed induction machines speed adjustment.Based on the analysis of the control theory of the DTC of doubly fed induction machines, in this paper , two control schemes are proposed: the least mode of rotor current and the stator power factor adjustable mode. In the first control scheme , we may make the rotor voltage the same or opposite phase with the rotor current by throwing suitable rotor voltage vector. Therefore . the unit rotor power factor can be implemented. In the second scheme, the stator power factor can be improved by adjusting the angle between rotor voltage and rotor magnetic linkage. In the paper, the detailed reasoning about the two schemes is carried on by analysis and experiment.The study about speed sensorless has been a important research aspect in the field of electric drive. Many methods have been found out. Some people think that the direct method is the most suitable way to doubly fed induction machine. In this paper, a direct method based on fixing the rotor current is proposed. By the experiment, we can prove that the method is correct.