Abstract
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.
Highlights
Power generation systems based on renewable energy sources, such as the solar photovoltaic (PV) and wind power plants (WPPs), present a non-dispatchable power generation characteristic.such systems are connected to the grid using power electronic inverters
This paper presented the design and comparison of seven topologies for ES-STATCOM realization based on modular multilevel converters
A comparison between Double-star chopper cell (DSCC)-distributed energy storage (DES) and DSCC-centralized energy storage (CES) topologies showed that DSCC-DES led to 55% higher ampacity and 30% higher volume than the DSCC-CES
Summary
Power generation systems based on renewable energy sources, such as the solar photovoltaic (PV) and wind power plants (WPPs), present a non-dispatchable power generation characteristic. Such systems are connected to the grid using power electronic inverters. Operational issues, such as voltage instability and instabilities during faults, harmonic resonances and flicker, may appear [1,2]. Apart from providing fast and dynamic reactive power support for improving voltage regulation, static synchronous compensators (STATCOMs) play an important role in improving voltage stability. STATCOMs provide the reactive current for low voltage ride through according to the relevant grid codes [3].
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