Resonance Stability Analysis of Hangzhou Flexible Low Frequency AC System

The modular multilevel matrix converter (M3C) based low frequency alternating current (LFAC) system is an attractive solution for the flexible interconnection in urban power grids. However, M3C stations show negative damping in certain frequency bands due to their fast control system dynamics. It is necessary to analyze the resonance stability when M3C stations are connected to the power grid. This paper aims at the resonance stability analysis of Hangzhou M3C based LFAC system. Firstly, port impedance models are built for both power frequency sides and low frequency sides by frequency domain scanning. Secondly, the resonance modes in the normal condition and some extreme conditions are calculated through the s-domain admittance matrix (s-DAM) method. The analysis indicate that all resonance modes have positive damping and no resonance instability risk exists in Hangzhou LFAC system.