Robust and Intelligent Control for Single-stage Grid-Connected Modular Multilevel Converter in PV Applications

• Published in: Journal of electrical engineering & technology Vol. 16; no. 2; pp. 917 - 931
• Main Authors: Hafez, Ahmed A., Mahmoud, Alaa A., Yousef, Ali M.
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 01.03.2021; 대한전기학회
• Subjects: Electrical Engineering; Electrical Machines and Networks; Electronics and Microelectronics; Engineering; Instrumentation; Original Article; Power Electronics; 전기공학; Modular Multilevel Converter; Active; PV; Grid; Reactive; Controller; Loads
• ISSN: 1975-0102; 2093-7423
• DOI: 10.1007/s42835-020-00639-8

Renewable Energy Resources (RESs) are frequently interfaced to the loads/grid via the standard two/three-level inverters. These inverter circuits to comply with the utility regulations must use volumetric and cumbersome filtering arrangements. Therefore, this article advises the application of Modular Multilevel Converter (MMC) for interfacing RESs in stand-alone and/or grid-connected operating modes. The MMC offers high quality voltage/current/power waveforms without additional filtering requirements, which possibly reduce the size/cost of the interfacing circuits. A simple and innovative active and reactive power control is proposed to drive the proposed MMC such that PV arrays operate at Maximum Power Point (MPP) under different climatological operating conditions. The proposed active-reactive control is implemented via Proportional Integral (PI) controllers; their parameters are defined via constraint optimization. Genetic Algorithm (GA) is used in this research to configure the PIs of the main controller. The objective function was designed to increase the stability margins of the system while reducing the overshoot. The proposed MMC has an extra freedom degree of generating/absorbing reactive power. The static and dynamic performances of MMC are analyzed via MATLAB and its dynamic platform, Simulink. The results showed that the proposed MMC produced significantly lower Total Harmonic Distortion (THD) than the three-level inverters. The static performance of the MMC showed that the THD decreases significantly with the increase of the converter level/sub-module number. The results raveled the robustness and effectiveness of the proposed controller, such that the PV generator operates at MPP while introducing high quality power/voltage to the loads/grid.