Analysis, Modeling an‎d Robust Control of Modular Multilevel Converters

11/14/2026 12:00:00 AM

This thesis focuses on the analysis, modeling, an‎d control of modular multilevel converters (MMCs), which are widely used in high-power applications such as HVDC transmission systems, renewable energy integration, an‎d medium-voltage motor drives. The complex structure of MMCs requires the control system to meet multiple objectives, including regulation of output currents, suppression of circulating currents, an‎d balancing of submodule capacitor voltages. Accordingly, this thesis examines limitations of conventional approaches an‎d proposes improved control strategies for MMCs. Specifically, two main control methods are proposed. The first is an optimal sliding mode control (OSMC) strategy that explicitly considers control input constraints, which are often neglected in conventional SMC designs. By formulating the control problem as a constrained quadratic programming (QP) problem an‎d solving it using the infeasible active-set (IAS) method, the OSMC ensures improved performance without exceeding control input limits. Offline simulation results in MATLAB/Simulink confirm that this approach outperforms conventional SMC methods. The second contribution is a linear matrix inequality (LMI)-based linear quadratic regulator (LQR), designed to han‎dle parameter uncertainties in MMC systems. Unlike classical LQR, this approach ensures robust performance by solving an LMI-constrained optimization problem. The proposed controller’s effectiveness is validated through real-time simulations on an OPAL-RT platform, demonstrating improved robustness under non-nominal conditions. Together, these contributions advance the state of MMC control by offering solutions that integrate constraint han‎dling, robustness, an‎d practical implementation considerations.

محدوديت‌هاي ورودي كنترل , نامساوي ماتريسي خطي , تنظيم‌كننده خطي درجه دوم , مبدل چندسطحي ماژولار , كنترل مُد لغزشي بهينه , عدم قطعيت پارامترها , برنامه‌ريزي درجه دوم , شبيه‌سازي بلادرنگ

Control Input Constraints , Linear Matrix Inequality (LMI) , Linear Quadratic Regulator (LQR) , Modular Multilevel Converter (MMC, M2C) , Optimal Sliding Mode Control (OSMC) , Parameters Uncertainty , Quadratic Programming (QP) , Real-Time Simulation

Homa SHEIKHI JOUYBARY

Davood ARAB KHABURI - Ahmed EL HAJJAJI