Research on a risk evaluation and suppression method for high-frequency resonance of flexible low-frequency transmission

Abstract

Due to the long delay of their control chains， voltage source converters （VSCs） in the high frequency band tend to show negative damping， which may give rise to high-frequency resonance when VSCs are connected to power systems. Flexible low-frequency alternating current transmission （LFAC） system adopts the modular multilevel matrix converter （M3C） as the core equipment and its high-frequency resonance risk needs to be evaluated. Based on practical engineering， this paper establishes the high-frequency impedance model of M3C. It evaluates the high-frequency resonance risk of the LFAC system under multiple operating modes through impedance analysis method. The operating conditions with high resonance risk are obtained， and the generation mechanism of the resonance is analyzed. Furthermore， a high-frequency resonance suppression strategy of installing an extra low-pass filter in the voltage feedforward control of M3C is proposed for practical engineering. Finally， the accuracy of the analysis results and the effectiveness of the proposed high-frequency resonance suppression strategy are verified by electromagnetic transient simulation.

Keywords

• modular multilevel matrix converter （m3c）
• flexible low-frequency alternating current transmission （lfac）
• high-frequency resonance
• control delay
• resonance suppression