A Fast State-of-Charge (SOC) Balancing and Current Sharing Control Strategy for Distributed Energy Storage Units in a DC Microgrid

Qin Luo, Jiamei Wang (), Xuan Huang and Shunliang Li
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Qin Luo: School of Electrical and Information Engineering, Yunnan Minzu University, Kunming 650504, China
Jiamei Wang: School of Electrical and Information Engineering, Yunnan Minzu University, Kunming 650504, China
Xuan Huang: School of Electrical and Information Engineering, Yunnan Minzu University, Kunming 650504, China
Shunliang Li: School of Electrical and Information Engineering, Yunnan Minzu University, Kunming 650504, China

Energies, 2024, vol. 17, issue 16, 1-21

Abstract: In isolated operation, DC microgrids require multiple distributed energy storage units (DESUs) to accommodate the variability of distributed generation (DG). The traditional control strategy has the problem of uneven allocation of load current when the line impedance is not matched. As the state-of-charge (SOC) balancing proceeds, the SOC difference gradually decreases, leading to a gradual decrease in the balancing rate. Thus, an improved SOC droop control strategy is introduced in this paper, which uses a combination of power and exponential functions to improve the virtual impedance responsiveness to SOC changes and introduces an adaptive acceleration factor to improve the slow SOC balancing problem. We construct a sparse communication network to achieve information exchange between DESU neighboring units. A global optimization controller employing the consistency algorithm is designed to mitigate the impact of line impedance mismatch on SOC balancing and current allocation. This approach uses a single controller to restore DC bus voltage, effectively reducing control connections and alleviating the communication burden on the system. Lastly, a simulation model of the DC microgrid is developed using MATLAB/Simulink R2021b. The results confirm that the proposed control strategy achieves rapid SOC balancing and the precise allocation of load currents in various complex operational scenarios.

Keywords: DC microgrid; droop control; distributed energy storage units (DESUs); line impedance mismatch; dynamic consistency algorithm; SOC balancing; current allocation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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