Energy Storage Units Optimal Operation Strategy with Efficiency Improvement and State of Charge Balance

The integration of numerous distributed energy storage units (ESUs) on a point of common coupling (PCC) necessitates more precise control. This includes ensuring state-of-charge (SoC) balancing across units while explicitly accounting for long-term efficiency. This paper presents a decentralized optimal operation strategy for ESUs, aiming to improve efficiency and ensure SoC regulation. Unlike traditional research on ESUs that focuses solely on SoC balancing, this approach integrates converter efficiency optimization by considering both converter efficiency characteristics and line resistance effects. A comprehensive power loss model is established, combining converter and network losses, and the efficiency-oriented power-sharing ratio is derived using the Lagrange multiplier method. The proposed strategy dynamically adapts to varying system conditions by switching optimal objectives of efficiency priority and SoC regulation. Real-time simulations and experimental results demonstrate that the strategy achieves efficiency improvement in paralleled ESUs while maintaining SoC deviations within the desired range, ensuring stable power-sharing and bus voltage operation under various scenarios, including sudden load changes and branch disconnections.