Frequency scanning of power electronic-based smart grids: the modular multilevel converter application

Multi-terminal HVDC systems are a key technology for bulk power transmission. The stability analysis of such power electronics-dominated power systems is a new challenge. This presentation focuses on an analysis based on the impedance representation of a modular multi-level converter (MMC). Therefore, a small-signal input impedance modelling method is described for high and low frequencies. A comparative evaluation with the impedance obtained via simulations was performed by the application of a voltage perturbation to the DC side. In addition, the stability of the interconnection of two MMCs in a back-to-back configuration was analysed by means of Nyquist criteria.