Open Access

ARTICLE

Automatic SOC Equalization Strategy of Energy Storage Units with DC Microgrid Bus Voltage Support

by Jingjing Tian¹, Shenglin Mo^1,*, Feng Zhao¹, Xiaoqiang Chen²

1 School of Automation & Electrical Engineering, Lanzhou Jiaotong University, Lanzhou, 730070, China
2 Key Laboratory of Opto-Technology and Intelligent Control (Lanzhou Jiaotong University), Ministry of Education, Lanzhou, 730070, China

* Corresponding Author: Shenglin Mo. Email:

Energy Engineering 2024, 121(2), 439-459. https://doi.org/10.32604/ee.2023.029956

Received 15 March 2023; Accepted 23 August 2023; Issue published 25 January 2024

Abstract

In this paper, an improved sag control strategy based on automatic SOC equalization is proposed to solve the problems of slow SOC equalization and excessive bus voltage fluctuation amplitude and offset caused by load and PV power variations in a stand-alone DC microgrid. The strategy includes primary and secondary control. Among them, the primary control suppresses the DC microgrid voltage fluctuation through the Ⅰ and Ⅱ section control, and the secondary control aims to correct the P-U curve of the energy storage system and the PV system, thus reducing the steady-state bus voltage excursion. The simulation results demonstrate that the proposed control strategy effectively achieves SOC balancing and enhances the immunity of bus voltage. The proposed strategy improves the voltage fluctuation suppression ability by approximately 39.4% and 43.1% under the PV power and load power fluctuation conditions, respectively. Furthermore, the steady-state deviation of the bus voltage, ΔU_dc is only 0.01–0.1 V, ensuring stable operation of the DC microgrid in fluctuating power environments.

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Keywords

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