Power Fluctuation Suppression Strategy for MMC‐SESS Based on Particle Swarm Rolling Optimisation

ABSTRACT

The modular multilevel converter with integrated supercapacitor‐based energy storage system (MMC‐SESS) has been considered promising to increase the stability of the renewable generation. However, power fluctuations in MMC‐SESS operation decrease the power quality and stability of the grid connection. In this paper, a rolling‐optimised fluctuation suppression strategy for MMC‐SESS is proposed. The instantaneous arm power model is first established, incorporating dual‐harmonic injection and associated parameter constraints. Based on this, the particle swarm optimisation algorithm is applied to obtain the best‐so‐far solutions of the main parameters in injected harmonics. Simulation verification shows that the proposed strategy can inject harmonics online as wind power fluctuates. It effectively suppresses arm power, submodule (SM) capacitor voltage, and SESS current fluctuations. It also extends the lifetime of the IGBT and supercapacitor. It also reduces the volume and cost of SM capacitors. These benefits demonstrate practical economic value for engineering applications.