基于动态特性对称补偿的并网变流器稳定控制方法

The asymmetrical vector control structure of the grid-connected converter leads to harmonic instability. In this paper, for the phase-locked loop (PLL) mainly affects the q-axis dynamics, it is proposed that the q-axis feedforward and the d-axis compensation control methods are adopted to decrease the asymmetric influence caused by the PLL based on the established complex signal impedance model. Similarly, for the DC-link voltage controller mainly affects the d-axis current reference, this paper proposes a d-axis feedforward and q-axis compensation method to improve the asymmetry dynamics introduced by the dc-link voltage controller. Considering that the proposed symmetrical control method will affect the frequency characteristics of the original system, the complex signal impedance model is used to analyze the feedforward and compensation method, obtaining the control method that has the least effect on the frequency characteristic of the original system. When the proposed methods are adopted, the components introduced by the PLL and the dc-link voltage controller in the coupling terms are eliminated, thereby improving the system stability. The theoretical analysis and the experimental results show that the proposed methods are effective.