Parameter stability region analysis of nonlinear link in primary frequency regulation process based on description function method

Abstract

For the primary frequency regulation process of power system, there are some key nonlinear links in the model. After the optimization and transformation of water turbine governor for suppressing ultra-low frequency oscillatory in southwest power grid, its ability to participate in power grid frequency regulation is weakened. And the amplitude and frequency limit of power grid frequency fluctuation are increased; the number of frequency crossing the deadband limit of primary frequency regulation is increased; and the influence of nonlinear link is prominent. The previous pure linear system analysis methods are difficult to carry out effective analysis. Based on this, the paper proposes to use the description function method to analyze the influence of nonlinear links in the system. The parameter stability regions of nonlinear links in different types of frequency regulation models are determined according to the improved Nyquist criterion. Firstly, the nonlinear transfer function models of primary frequency regulation for different types of hydropower, thermal power, and direct current FC are established. This paper summarizes the structural similarity of nonlinear links of different primary frequency regulation resources, and the steps of analyzing its nonlinear link are put forward, and the corresponding simulation verification is carried out.