Optimization-Based Cell Selection Method for Grid-Connected Modular Multilevel Converters
2016 (English)In: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 31, no 4, 2780-2790 p.Article in journal (Refereed) PublishedText
Modular multilevel converters (MMCs) are widely used in different applications. Due to low-loss operation, compactness, and high modularity, MMC is extremely attractive for high-voltage direct-current (HVDC) transmission systems. The HVDC station loss is highly related to the converter switching pulse pattern, which is generated by modulation algorithm and cell selection methods. This paper formulates the switching pulse pattern generation, as a versatile optimization problem. The problem constraints and objectives are formulated for HVDC applications and compared with similar problems in the field of computer science. To overcome the computational complexity in solving the introduced optimization problem, a heuristic method is proposed for cell selection algorithm. The method utilizes the current level in order to obtain lossless switching at zero-current crossings. The study of the proposed method, in a time-domain simulation platform, shows that the method can reduce the switching converter losses by 60% compared to carrier-based modulation, maintaining the same capacitor voltage ripple. Eventually, the practical functionality of the proposed method is verified in a real-time digital simulator, RTDS, for a 512-level converter in a point to point HVDC link. Although this paper focuses on HVDC, the mathematical model is applicable for any MMC application.
Place, publisher, year, edition, pages
IEEE , 2016. Vol. 31, no 4, 2780-2790 p.
High-voltage direct-current (HVDC) transmission, modular multilevel converter (MMC), power conversion, switching frequency, switching loss, zero-current switching
Electrical Engineering, Electronic Engineering, Information Engineering
IdentifiersURN: urn:nbn:se:kth:diva-180195DOI: 10.1109/TPEL.2015.2448573ISI: 000365953100009ScopusID: 2-s2.0-84960095195OAI: oai:DiVA.org:kth-180195DiVA: diva2:895949
QC 201601202016-01-202016-01-082016-09-16Bibliographically approved