Advanced Control Strategies and Topology Analysis of Multi-Cell Converters for Power Electronic Applications

The growing need for reliable, efficient power conversion in high-voltage, high-power applications has accelerated the development of new converter topologies and control methods. This paper provides a comprehensive analysis of multicellular (series multicell) converters, focusing on their topologies, mathematical modeling, and advanced control methods in both chopper and inverter setups. The multicellular converter topology offers many advantages, including distributed voltage stress, modularity, improved output waveform quality, and enhanced dynamic performance. However, to ensure the system runs smoothly, it needs advanced control systems to maintain balanced floating-capacitor voltage and respond effectively to changing or disturbed conditions. Two mathematical modelling approaches—instantaneous and average value models—are developed for the series multi-cell converter. Building on these, three control strategies are proposed and analyzed: open-loop natural balancing, closed-loop proportional-integral (PI) regulation for floating capacitor voltages, and a robust sliding-mode control integrating decoupled current and voltage regulation. The phase-shifted pulse-width modulation method is used to implement these controllers, and detailed MATLAB/Simulink simulations of a three-cell converter driving an R-L load are used to test them. The results show that advanced control techniques have led to significant improvements, including faster dynamic response, better voltage balancing, less variation in output voltage and current, and greater resistance to disturbances. The paper lays the groundwork for the use of multicellular converters in renewable energy systems. Future work will focus on integrating a three-arm inverter into wind turbine conversion chains, further reducing control chattering and testing performance in real-world conditions.