Modeling and Control of Modular Multilevel Converters' Current Dynamics via Modified Nodal Analysis and Linear Quadratic Regulator

This paper addresses the challenges associated with the modeling and control of modular multilevel converters (MMCs), which excel in handling high-power density while minimizing harmonic distortion due to their inherent modularity, scalability, and superior waveform quality. To harness these benefits, a comprehensive methodology that combines modified nodal analysis (MNA) for precise full-state-space modeling of MMCs with an optimized linear quadratic regulator (LQR) for effective control is proposed in this paper. The MNA method systematically describes the dynamic behavior of currents within the MMC, accommodating its complex electrical components. Facing the challenge of high-dimensional state-space models, a dimension-reduction technique to simplify model structure without compromising accuracy is introduced. The LQR control strategy is tailored to the MMC's state-space representation, focusing on cost-function design to ensure rapid transient response, minimal steady-state error, and outstanding dynamic performance. Simulation results validate the effectiveness and reliability of the proposed approach. This study contributes valuable insights into advancing power electronics and supports the ongoing development of technologies for integrating renewable energy sources into the power grid.