Global matrix method for frequency-domain stability analysis of hydropower generating system

Abstract

Safe and stable operation of hydropower plants is the basis and prerequisite of great importance for clean energy production and integration of renewables. To better analyze the operating stability of hydropower generating systems (HGSs), a novel frequency-domain method (global matrix method) is proposed in this paper. First, the principle of the new method and the mathematical models of each common hydraulic component in HGSs are presented. Second, three general steps for deriving the global matrix of an arbitrary system and order-reduction and numerical calculation of the matrix are illustrated in detail. In two case studies of HGS stability analysis, the transfer function method (TFM) suitable for time-frequency domain analysis is applied to evaluate the global matrix method. For simple single-unit system, the new method is compared by the TFM from both frequency domain and time domain. For complicated multi-unit system, the TFM is not applicable to the frequency-domain stability analysis, and only the time-domain simulation is applied to verify the new method. The results indicate that the stability regions by the two methods are in good agreement, verifying the accuracy of the new approach. The proposed method can replace the TFM for stability analysis of HGSs in frequency domain, outperforming the latter in applicability, flexibility, and quantification function.