Arm equivalent circuit based and average arm model of a DC MMC branch including distributed energy storage submodules to integrate energy storage in HVDC system

Abstract

Energy Storage Systems (ESSs) integrated in high voltage direct current (HVDC) applications are a promising approach for power systems dominated by power electronics and non-dispatchable resources. This paper focuses on modular multilevel converter (MMC) with distributed energy storage modules directly connected to MMC modules (ES-SMs). It presents an arm equivalent circuit-based model and an arm average model of a branch of ES-SMs. The simplified detailed model developed in this paper provides trade-off between a representation of the behaviour of each individual ES-SM and reducing the computing resources requirement. This model is well-suited for studies such as converter loss calculations and analysis of balancing algorithms between ES-SMs. In contrast, the average model reduces the number of state variables, making it more suitable for system-level studies. The simplified detailed model is developed with an algorithm for balancing the voltages of the capacitors of the ES-SMs and the states of charge/energy of the storage elements. In addition, an off-line script has been designed to estimate the converter losses. Simulations are first used to validate the effectiveness of the simplified detailed model of the branch of ES-SMs and its control, before performing other simulations to make a comparison with full and average models. The detailed simplified model and the simplified model are validated against full detail model.

Sidlawendé Ouoba, Florian Errigo, Heitor Farias de Barros, Ahmed Islam Zama, Joan Sau Bassol, Florent Morel, Pierre Rault, Abdelkrim Benchaib, Xavier Bourgeat

Presented at CIGRE Symposium Trondheim 2025

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