Research on the Impacts of Digital Control Delay on the Effectiveness of Current Loop Decoupling

Abstract

This paper analyzes the effect of digital control delay on the effectiveness of current loop decoupling (feed-forward decoupling and complex vector PI decoupling) in the synchronous rotating frame, revealing the nature of the decoupling failure under the condition of low switching frequency or high control frequency. And the delay compensation method for suppressing the current loop coupling is proposed. The advantages and disadvantages of the two decoupling methods are then compared in term of the decoupling effectiveness and the dynamic response speed of the current loop. Compared to the feed-forward decoupling, the coupling between d axis and q axis of complex vector PI decoupling is reduced by 50%, and the dynamic response speed is about twice. Simulation and experimental results are carried out to verify the correctness of the theoretical analysis.