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

The Multi-terminal HVdc systems is a key technology for bulk power transmission. The stability analysis of such power electronics-dominated power systems is a new challenge. This paper focuses on the analysis based on impedance representation of a modular multilevel converter. Therefore, a small signal input impedance modeling 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 analyzed by means of Nyquist criteria.