Energy-Based Full-State Feedback Linear Control for Modular Multilevel Converters With Improved Damping and Reduced Model Order

Modular multilevel converters (MMCs) are widely utilized in high-power conversion applications. Typically, a cascaded proportional-integral (PI) control scheme is employed for the regulation of the MMC’s dc-bus voltage, which is based on a second-order system model. However, achieving an optimal balance between dynamic performance and disturbance rejection using such schemes poses significant challenges. Moreover, MMCs often exhibit substantial energy nonlinearity, especially at the high-voltage dc-bus, which further complicates their operation and control. To address these issues, this article introduces a full-state feedback control (FSFC) strategy specifically designed for MMCs. The proposed method involves constructing an energy-based model to linearize the dc voltage control process. By incorporating full-state variable feedback, the FSFC reduces equivalent system model order, thereby enhancing disturbance suppression and accelerating response times. The article also presents the block diagram of the FSFC, determining the state feedback gain that yields optimal damping characteristics. Comparative analysis of the cascaded PI control and the proposed FSFC is performed under identical crossover frequencies and phase margins. Simulation and experimental results confirm that the FSFC offers superior advantages in terms of dynamic response and stability compared with existing advanced control schemes.