Analysis of the Inter-Submodule Active Power Disparity Limits of Modular Multilevel Converter-Based Battery Energy Storage Systems

Tafti

IEEE Trans. Ind. Electron.

et al. 2022

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In the operation of cascaded H-bridge (CHB) converters and modular multilevel converters (MMCs) with energy storage or renewable power resources, unbalanced active power distribution among the submodules (SMs) is unavoidable. Depending on the operating conditions, there are certain upper and lower limits on the active power that can be processed by a single SM or a subset of SMs. The control system needs to restrict the SM power references to these limits, hence, accurate knowledge of the power limits is important. In existing methods to derive the power limits, the SM capacitor voltages are assumed to have negligible ripples, whereas in practice the ripples can be considerable. This paper analyzes the effect of capacitor voltage ripples on the SM active power control limits and highlights the importance of considering the ripple effect. A methodology is proposed to accurately incorporate capacitor voltage ripples in the derivation of SM active power control limits. Simulation and experimental results are provided to evaluate the effectiveness of the proposed methodology. Index Terms-Active power control limits, cascaded H-bridge, capacitor voltage ripple, hybrid integration of energy sources, modular multilevel converter.

Section: (B) Depictsmentioning

confidence: 99%

Effect of Capacitor Voltage Ripples on Submodule Active Power Control Limits of Cascaded Multilevel Converters

Tafti

IEEE Trans. Ind. Electron.

et al. 2022

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“…Depending on the operating condition of the converter, there are certain upper and lower limits for the amount of active power that can be processed by a subset of SMs, i.e. each single SM or any multiple SMs of the converter [12]. If the SM power references exceed the limits, the power distribution is unviable, which means the SMs will fail to track their references.…”

Section: Sm Imentioning

confidence: 99%

Unbalanced Active Power Distribution of Cascaded Multilevel Converter-Based Battery Energy Storage Systems

IEEE Trans. Ind. Electron.

Ceballos

et al. 2022

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In a battery energy storage system (BESS) based on the cascaded H-bridge (CHB) converter or modular multilevel converter (MMC), the active power distribution among the submodules (SMs) can be highly unbalanced, especially when batteries with different power ratings are used. Meanwhile, there are certain limits for the unbalanced power distribution among the SMs. It is a challenge to determine whether the active power distribution is viable for cascaded multilevel converters with unequal capacitor voltages because the complexity grows exponentially as the number of SMs increases. This paper proposes a generalized analytic solution to this problem, which reduces the complexity significantly and is readily applicable to converters with large number of SMs. The validity of this method is proved theoretically and verified with simulation and experimental results on both the MMC and CHB converter.

“…As reported in [7], [8], there exist certain limits for the amount of active power that can be processed by a subset of SMs in one arm of the MMC. The fault tolerance of an MMC-based BESS is decided by the active power limits of SMs.…”

Section: Assessment Of Battery Fault Tolerancementioning

confidence: 99%

“…In other words, the battery fault tolerance of an MMC-based BESS can be assessed with the knowledge of the SM active power limits. The derivation of active power limits of half-bridge SMs has been analyzed in [7], [8]. This section first extends the analysis to full-bridge SMs and then investigates the battery fault tolerance for both choices of SMs.…”

Section: Assessment Of Battery Fault Tolerancementioning

confidence: 99%

See 1 more Smart Citation

A Comparison of the Battery Fault Tolerance of Modular Multilevel Converters with Half-Bridge and Full-Bridge Submodules

2021 IEEE Energy Conversion Congress and Exposition (ECCE)

Gorla

et al. 2021

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