IGCT-Based Direct AC/AC Modular Multilevel Converters for Pumped Hydro Storage Plants

Vasiladiotis, Michail; Baumann, Remo; Haderli, Christoph; Steinke, J.K.

doi:10.1109/ecce.2018.8557594

Cited by 21 publications

(31 citation statements)

References 10 publications

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“…However, in reality this is unfeasible as the 3x3-MMSC is not capable of operating in the boost mode. So, the theoretical limit for designing the 3x3-MMSC is the one described in equation (5).…”

Section: Improved Converter Topologymentioning

confidence: 99%

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Novel Converter Topology With Reduced Cost, Size and Weight for High-Power Medium-Voltage Machine Drives: 3x3 Modular Multilevel Series Converter

et al. 2021

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The modular multilevel converter is considered the state-of-the-art power electronic solution for high-power high-voltage applications that require a DC stage and that operate with fixed frequency at their AC terminals. However, in high-power AC-AC variable-frequency applications, it has been proved that this converter topology presents an unnecessarily large number of components and an intolerably high submodule-capacitor voltage ripple at low frequencies. The modular multilevel matrix converter was proposed as a promising alternative for high-power medium-voltage electrical-machine drives since it presented improved performance at low frequencies and a reduced number of components in comparison to the modular multilevel converter resulting in reduced costs and improved efficiency. Even though, the modular multilevel matrix converter is one of the converter solutions that stands out the most for high-power machine drives, it presents some operational drawbacks such the unstable behavior under unbalanced grid conditions and the extremely complex internal control and modulation. Recently, a new converter topology named modular multilevel series converter was proposed presenting attractive operational characteristics such as the high performance at low frequencies, high performance under unbalanced grid conditions, and straightforward control and modulation, which are important advantages compared to the modular multilevel converter and the modular multilevel matrix converter. Nonetheless, as demonstrated in this paper, the modular multilevel series converter presents large component count and poor efficiency. Thus, in this paper, a new converter solution is proposed, which is an enhanced version of the modular multilevel series converter that preserves the previously mentioned advantageous operational characteristics and that presents an improved efficiency and a considerably reduced number of components in comparison to the other three converter topologies, resulting in reduced cost, size and weight.

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Section: Improved Converter Topologymentioning

confidence: 99%

“…The amplitude of the grid voltage, connected to the input terminals of the 3x3-MMSC, should be designed according to equation (5), which means that, ideally, V g = V o . However, similarly to the other topologies, a voltage margin is considered and, thus, V g = 1.25(V o ) is adopted for the 3x3-MMSC design.…”

Section: X3-mmsc 1) Number Of Componentsmentioning

confidence: 99%

Novel Converter Topology With Reduced Cost, Size and Weight for High-Power Medium-Voltage Machine Drives: 3x3 Modular Multilevel Series Converter

et al. 2021

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“…MMC was first developed for and deployed in highvoltage DC inter-ties, where typically low-loss Half-Bridge (HB) Submodules (SMs) are utilized as converter building blocks [12], [13]. In PHSP AC-AC application of interest, either a matrix-like Direct-MMC [14], or a back-to-back (Indirect-)MMC can be considered [10]. While Direct-MMC is superior for new installations with differing machineand grid-side frequencies, Indirect-MMC is more suitable for similar frequency values [15], [14].…”

Section: Introductionmentioning

confidence: 99%

“…In PHSP AC-AC application of interest, either a matrix-like Direct-MMC [14], or a back-to-back (Indirect-)MMC can be considered [10]. While Direct-MMC is superior for new installations with differing machineand grid-side frequencies, Indirect-MMC is more suitable for similar frequency values [15], [14]. As retrofit ideally presumes keeping the original machine, Indirect-MMC is the preferred topology (Fig.…”

Section: Introductionmentioning

confidence: 99%

Hybrid Modular Multilevel Converter Design and Control for Variable Speed Pumped Hydro Storage Plants

Basic¹,

Utvić

Dujić

2021

IEEE Access

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Hybrid modular multilevel converter control and design for pumped hydro storage plants is presented, addressing application-specific shortcoming of conventional back-to-back half-bridge modular multilevel converter: high common-mode-voltage machine stress. Common-mode-voltage-free operation in the entire or partial frequency range is enabled by variable DC link voltage control, through introduction of minimal full-bridge submodule share in hybrid active front-end converter stage. The developed generalized converter design approach for arbitrary DC link voltage range operation and additional internal energy balancing control layers enable down-to-zero DC voltage control. The results are verified through highfidelity switched-model simulations of 6 kV converter, with 10/6 ratio of full-bridge to half-bridge submodules in active front-end. The analyzed hybrid active front-end stage benefits from lower converter losses for equal machine operation flexibility compared to full-bridge design, while trade-off between gridside power factor range and full-bridge submodule share is offered within the design stage. Compared to the state-of-the-art, zero-to-rated DC link voltage operation is possible at lower full-bridge submodule share (62 % against 75 %), at the penalty of reduced grid-side power factor. Alternatively, operation at higher fullbridge submodule share (62 % against 50 % existing solution) enables grid-side reactive power support over wide speed range, without branch current overload.INDEX TERMS Hydroelectric power generation, modular multilevel converter, retrofit.

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“…In AC-AC applications, such is a gridconnected drive of the PHSP, either a matrix-like Direct MMC (D-MMC), or a back-to-back Indirect MMC (I-MMC) can be considered. D-MMC is an efficient solution if machine-and grid-frequency differ, making it suitable for new installations, with unrestricted choice of machine parameters [8].…”

Section: Introductionmentioning

confidence: 99%

Highly Flexible Indirect Modular Multilevel Converter for High Power Pumped Hydro Storage Plants

Basic

Schwery

Dujić

2020

IECON 2020 the 46th Annual Conference of the IEEE Industrial Electronics Society

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As fossil-fuel-and nuclear-based generating facilities are being phased-out in favor of intermittent renewable energy sources, the need for large scale, highly flexible balancing storage is imminent. By the generating capacity of readily available units, enormous potential lays in retrofitting of large pumped hydro storage plants to variable speed operation, increasing their flexibility to meet future power system demands. Indirect Modular Multilevel Converter is a highly scalable and inherently redundant topology that meets the power and voltage ratings of large pumped hydro generating units. Variable DC link converter operation, offering common-mode-free machine-side operation has been evaluated, considering constraints in retrofit of old machines, not designed for converter-fed operation. Performance evaluation over the entire operating range of the plant is performed. Grid support dynamics has been assessed. Finally, application-specific challenges in the design stage are pointed out.

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IGCT-Based Direct AC/AC Modular Multilevel Converters for Pumped Hydro Storage Plants

Cited by 21 publications

References 10 publications

Novel Converter Topology With Reduced Cost, Size and Weight for High-Power Medium-Voltage Machine Drives: 3x3 Modular Multilevel Series Converter

Novel Converter Topology With Reduced Cost, Size and Weight for High-Power Medium-Voltage Machine Drives: 3x3 Modular Multilevel Series Converter

Hybrid Modular Multilevel Converter Design and Control for Variable Speed Pumped Hydro Storage Plants

Highly Flexible Indirect Modular Multilevel Converter for High Power Pumped Hydro Storage Plants

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