Analysis and optimization of hybrid modular multilevel converters under over-modulation conditions. (March 2020)

• Record Type: Journal Article
• Authors: Hu, Pengfei; He, Zhengxu; Yin, Rui; Guo, Jie; Guerrero, Josep M.; Teodorescu, Remus
• Is Part Of: International journal of electrical power & energy systems. Volume 116(2020)
• Publication Date: 2020-03
• Subjects: Hybrid modular multilevel converters -- Over-modulation -- Optimization of modulation index -- Voltage ripple; Electrical engineering -- Periodicals; Electric power systems -- Periodicals; Électrotechnique -- Périodiques; Réseaux électriques (Énergie) -- Périodiques; Electric power systems; Electrical engineering; Periodicals; 621.3
• DOI: 10.1016/j.ijepes.2019.105578
• Languages: English
• ISSNs: 0142-0615

Abstract

Highlights: An improved wave-distributing approach to reduce the loss of the two types of SMs is proposed. Capacitor voltage fluctuations of the FBSMs and HBSMs in hybrid MMCs are analyzed. Optimization of the ratio of the AC voltage to the DC voltage is proposed. Abstract: This paper firstly analyzes the operating principles of a hybrid modular multilevel converter (MMC) which utilizes a combination of half-bridge submodules and full-bridge submodules, and proposes an improved modulation method. After that, the capacitor voltage fluctuation of sub-module is comprehensively analyzed in over-modulation condition. Furthermore, according to the above analysis, the optimal modulation index resulting in the smallest capacitor voltage ripple is derived based on the proposed mathematical relationship. In order to verify the proposed modulation method, capacitor voltage fluctuation analysis and modulation index optimization, a PSCAD/EMTDC based simulation model is constructed and some experiments are carried out on a scaled-down hybrid MMC prototype. Both simulation and experimental results confirm the correctness of the analysis and optimization.