Benchmarking of Modular Multilevel Converter Topologies for ES-STATCOM Realization

In recent years, the integration of the high-power static synchronous compensator (STATCOM) and energy storage in the same device has gained interest. Such a system is referred to as ES-STATCOM. Modular multilevel converter (MMC) topologies constitute a promising converter family for ES-STATCOM realization, providing a modular and scalable solution with a high efficiency that handles high-power and high-voltage ratings in grid applications. There is a gap in technical literature discussing the design and the comparison of MMC-based ES-STATCOMs while utilizing batteries to find the most suitable MMC topology for ES-STATCOMs. Therefore, this paper benchmarks MMC family members for ES-STATCOM realization. Both centralized and distributed energy storage approaches are investigated. The proposed design flowcharts can be employed for comparison and optimization purposes. In total, seven topologies are compared in terms of number of cells, required silicon area and total battery volume. Different semiconductor devices and battery types are analyzed. The result indicates that centralized energy storage systems are the most suitable due to their design flexibility, low volume and small silicon area. Moreover, the possibility of using over-modulation in MMC using bridge cells has an important role in the optimization of ES-STATCOM. The results for the adopted case study shows that the decentralized approach can lead to 55% higher silicon area and 30% higher volume than the centralized approach. The double-star bridge cell MMC with centralized energy storage is determined as the most suitable solution for ES-STATCOM systems.