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DC-Side Impedance Interaction Analysis in an MMC-Based Back-to-Back VSC-HVDC System

In this paper, harmonic stability of a back-to-back modular multilevel converter based voltage source converter high voltage direct current system is analyzed. These systems are prone to ac- and dc-side resonances and interactions between the converter and its interconnected systems. The stability of the system can be predicted by the impedance based stability criterion, which requires the modeled or measured converter impedance. The analysis in this paper focuses on interoperability when the converters employ different control schemes in order to utilize the inherent damping properties of the sum capacitor voltage balancing control loops.