Simplified Indirect Model Predictive Control Method for a Modular Multilevel Converter

• Published in: IEEE access Vol. 6; pp. 62405 - 62418
• Main Authors: Nguyen, Minh Hoang, Kwak, Sangshin
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2018; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Alternating current; Capacitors; circulating current; computational load; Control methods; Converters; Cost function; Dynamic response; Metal matrix composites; Model predictive control (MPC); modular multilevel converter (MMC); Modularity; Predictive control; preselection; Sorting; Sorting algorithms; Switches; Voltage control
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2018.2876505

Demand for modular multilevel converters (MMCs) has been steadily increasing for utilization in medium- to high-power applications because of qualities such as high modularity, easy scalability, and superior harmonic performance. Furthermore, there has been a growing trend toward utilizing model predictive control for MMCs due to its simplicity, good dynamic response, and ease of multi-objective control. However, the rise in computational load leads to a great drawback when increasing the number of submodules (SMs). This paper presents an approach to reducing the computational load and using on-state SMs and circulating currents, by preselecting the number of SMs inserted in the upper and lower arms. This approach is based on using the number of on-state SMs and the circulating current, to compute the number of SMs inserted in the upper and lower arms, which is evaluated in the next sampling instant. This facilitates a significant reduction in the number of control options and the computational load. A sorting algorithm is used to retain the balancing capacitor voltages in each SM, while the cost function guarantees the regulation of the ac-side currents, arm voltages, and MMC circulating currents. Simulation and experiment results validate the performance of the proposed approach.