Small Signal Model of Modular Multilevel Converter with Power Synchronization Control

Power synchronization control (PSC) is one of the popular control schemes in grid-forming control-based converters because it simulates the grid support capability of conventional synchronous generators. However, prior research is based on two-level converters which do not have complex internal circuits, and whether PSC can be directly applied to the modular multilevel converter (MMC) topology since MMC has sub-module capacitor voltage ripples and inherent second harmonic circulating current algorithm, has not been analyzed. This paper establishes the small signal model of MMC with PSC considering the MMC internal dynamic and circulating current suppression control (CCSC). The power oscillation phenomenon when grid short-circuit ratio (SCR) increases is also demonstrated with the closed-loop system eigenvalues calculation and verified with the experimental results.