Control and Experimental Validation of the Series Bridge Modular Multilevel Converter for HVDC Applications

Abstract

The Series Bridge Converter (SBC) is a modular multilevel converter recently developed to enhance power density in high voltage, high power applications. The Modular Multilevel Converter (MMC) is a well established solution, widely researched and exploited in practical HVDC connections thanks to its high power quality and high efficiency. However, the main limitation of the MMC is the relatively large energy storage, also due to the fact that power ripples in the sub-module capacitors include a component at the fundamental AC frequency. As a result, volume becomes critical in applications such as offshore or city centre in-feeds where space is restricted and expensive. The SBC offers a more compact footprint by exploiting a series connection on the DC side and by operating the sub-modules with rectified waveforms, thus moving the minimum component of the instantaneous power to twice the AC fundamental and reducing capacitors size. The drawback of the converter is a more complex energy control compared to the MMC. This paper proposes the first experimental validation of the SBC, using a 2kW laboratory-scale prototype. Since the basic converter design has been discussed in previous papers, the focus of this work is on converter control design and experimental validation.

Modular Multilevel Converters for Large-Scale Grid-Connected Photovoltaic Systems: A Review

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“…To reduce the number of submodules, various topologies with a series connection of converter phases have also been introduced. Among them, the most prominent are the Parallel Hybrid Modular Multilevel Converter (PH-MMC) [17]- [18] and the Series Bridge Converter (SBC) [19]- [20]. Due to the coupling between AC-and DC-side voltages in the PH-MMC resulting in a fixed modulation index, the control of the AC output voltage is achieved by adding third harmonic components in the reference voltages [17].…”

Semi‐hot redundant control method for modular multilevel converter‐based high‐voltage direct current systems under submodules fault

“…Modular multilevel converters (MMCs) represent a popular topology of voltage source converters in high-voltage direct current (HVDC) transmission systems [1][2][3][4][5][6]. MMC-HVDC systems typically involve a large number of submodules (SMs).…”