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Complex Vector Modeling and Series Decoupling Current Control Strategy of High-Power L/LCL Type Grid-Connected Converter Under Low Switching Frequency
Yingjie Wang*,**, Lanyi Jiao*, Bo Yang*, Wenchao Wang***, and Haiyuan Liu˘Ó
Abstract With power level of grid-connected converters rising, the switching frequency of the switching devices is commonly greatly reduced to improve its power capacity. However, this results in serious couplings of the dq current components, which leads to degradation of the static and dynamic performances of grid-connected converters and fluctuations of the reactive power in dynamic processes. In this paper, complex vector models under low switching frequency are established for an L/LCL grid-connected converter, and the relationship between the switching frequency and the coupling degree is analyzed. In addition, a series decoupling current control strategy is put forward. It is shown that the proposed control strategy can eliminate the couplings, improve the performances and have good robustness to parameter variations through static and dynamic characteristics analyses and a sensitivity analysis. Experimental and simulation results also verify the correctness of the theoretical analyses and the superiority of the proposed control strategy.
Keyword Complex vector, Decoupling current control strategy, Low switching frequency
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