Accurate current sharing with SOC balancing in DC microgrid

• Published in: Electric power systems research 2024-07, Vol.232, p.110386, Article 110386
• Main Authors: Wang, Kai, Zhang, Jiyong, Qiu, Xianqun, Wang, Jiakang, Wang, Chuanyuan
• Format: Article
• Language: English
• Subjects: Current sharing; DC microgrid; Droop control; State of charge (SOC); Voltage restoration
• ISSN: 0378-7796; 1873-2046
• DOI: 10.1016/j.epsr.2024.110386

•In this paper, the effect of mismatched line impedances in the system on the precise current distribution among ESUs is considered. A current compensation term is introduced into the droop coefficient. By adjusting the weight of the compensation term, precise current distribution among the energy storage units is achieved on the basis of rapid equilibrium.•The control strategy proposed achieves precise current distribution by altering the droop coefficient. Compared to traditional current distribution strategies, the use of proportional-integral controllers can be reduced. In the presented study, a novel droop control method has been developed for distributed energy storage systems, which ensures the precision of current sharing and the balance of state of charge (SOC). A strategy that has been newly introduced facilitates a logical allocation of SOC and ensures precise sharing of current in autonomous island DC microgrids. Within the framework of droop control, a linkage is established between the SOC value and the converter's output current. By mitigating the impact of disparate line impedance on SOC equilibrium, the service life of energy storage units (ESUs) is significantly improved. The droop coefficient has been augmented with the inclusion of a current compensation term. It has been ascertained that the ratio of SOC to output current within the droop coefficient can be determined independently, utilizing the state information of SOC. By incorporating accurate current sharing that considers SOC, ESUs with higher SOC levels output larger currents, while those with lower SOC levels output smaller currents. A newly devised control approach is distinguished by its reliance on low-bandwidth communication. This method ensures the stabilization of the DC bus voltage, maintaining it at a pre-set level, achieved through the application of a voltage restoration technique.