A black-box method for the stability analysis of multi-inverter-fed power systems using Bode diagrams

Abstract

A multi-inverter-fed power system is susceptible to small-signal instability owing to weak grid influence. This study proposes a black-box method for small-signal stability analysis of a multi-inverter-fed power system based on Bode diagrams. Not only did it consider the technical confidentiality on the engineering site, but it also took into account the presence of right-half-plane (RHP) pole in the aggregated impedance, achieving Nyquist circle acquisition through Bode diagrams. The stability analysis process is thus more accurate, intuitive, and convenient. First, black-box impedance fitting for a single grid-connected inverter and impedance aggregation for a multi-inverter-fed power system are discussed. Second, the principle of the proposed method is elaborated. Using the Bode diagram, the number of RHP poles of the aggregated impedance and actual number of circles for Nyquist curves are identified. Third, a multi-inverter-fed power system is constructed, and the effectiveness of the proposed method is verified using case analysis and hardware-in-the-loop real-time experiments based on RT-LAB. Finally, the advantages of the proposed method are revealed by comparing it to the IF method.