Repetitive control without inductance decoupling for VSR control strategy of DC charging pile

Abstract

A control strategy of repetitive control without inductorance decoupling was proposed to address the problem of high total harmonic distortion(THD) rate of the network-side current caused by the reduced stability of the rectifier module of the DC charging pile under weak grid as well as the dead zone and nonlinearity of switching devices during charging. Firstly, the parallel repetitive control was constructed in the inner current loop, and the proportional-integral(PI)+ repetitive controller based on parallel structure was designed. For system compensation, a second-order low-pass filter was selected to correct the system, and the network-side current harmonics were actively suppressed without increasing the filtering device, which effectively improves the quality of grid-connected current. Secondly, based on the synthetic vector method, the controller parameters were designed to realize the elimination of main pole by establishing two synchronous rotation coordinate system vector differential equations, so as to realize the inductanceless decoupling to cope with the influence of network-side inductance fluctuation on the stability of the control system under weak grid. By theoretical analysis and simulation, the proposed control strategy was embedded into the self-developed digital signal processor for the rectifier module of DC charging pile, simulated dynamic and steady-state operation experiments were conducted, and comparative analysis was performed to prove the feasibility of the proposed control strategy.

Keywords

weak grid / DC charging pile / voltage source rectifier (VSR) / repetitive control / inductanceless decoupling

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