SHAN Changshuai, GENG Qiang, ZHAO Chendong, JIANG Ke

 

(School of Electrical Engineering and Automation, Tianjin Polytechnic University, Tianjin 300387, China)

 

 

Abstract: Aiming at the problem that the original offgrid type wind power generation systems in some remote areas were in urgent need of expansion, a novel common DC bus cascade rectifier device was proposed, and the simultaneous parallel operation of two generators can be achieved based on the device. The topological structure of the novel cascade rectifier device, the commutation process of the generator′s current, and the computing method of duty cycle were studied. The relationship between the speed of generator and the output average voltage of uncontrolled rectifying circuit was established. The operating states in series or in parallel of the two generators were analyzed and concluded in detail. Meanwhile, the switching method of state based on the hysteresis loop principle was proposed. In addition, the system was verified by simulation using Matlab. The results indicate that the device can change the working modes of the two generators according to the different speed of the generators, expand the speed adjustable range of generators and increase the capacity of system effectively, at the same time, the device allows that the duty cycle of power switching device operates in the reasonable range, avoids the occurrence of narrow pulse, decreases the highorder harmonics and improves the system performance.

 

Key words: permanent magnet generator; wind power generation; offgrid type; cascade rectifier