Abstract: Interconnected systems have attracted significant attention in numerous engineering applications such as energy, water, and oil, as well as gas distribution networks. However, due to their high complexity, it is enormously difficult to ensure a reliable and effective cooperation of such interconnected systems under limited communication and interaction capacities. In addition, uncertainty consideration poses further challenges in developing an efficient distributed optimization approach to such interconnected systems. Furthermore, satisfying the constraints of shared states between subsystems under uncertainty leads to conflict issues and has not been properly studied yet. This study proposes a chance-constrained distributed optimization approach to the optimal operation of interconnected systems by considering conflicting reliability levels of satisfying shared state constraints. A compromised reliability level for such constraints is determined by an averaged weighting. We establish that the optimal cost is Lipschitz-continuous with respect to the compromised reliability level, providing a theoretical basis for quantifying the marginal cost of reliability, and we show that the compromise is robust to perturbations in the subsystem weights. We develop a numerical solution framework based on the inner–outer approximation method. For the efficient computation of the high-dimensional integrals, we use Hoeffding’s inequality to determine a suitable sample size. The optimal operation of three interconnected energy distribution networks is used as a case study to demonstrate the proposed approach.

Nteutse, P.K.; Mugenga, I.R.; Geletu, A.; Li, P. Novel Ordinary Differential Equation for State-of-Charge Simulation of Rechargeable Lithium-Ion Battery.

Appl. Sci.2024, 14, 5284. https://doi.org/10.3390/app14125284

© Pu Li

Abstract: Lithium-ion battery energy storage systems are rapidly gaining widespread adoption in power systems across the globe. This trend is primarily driven by their recognition as a key enabler for reducing carbon emissions, advancing digitalization, and making electricity grids more accessible to a broader population. In the present study, we investigated the dynamic behavior of lithium-ion batteries during the charging and discharging processes, with a focus on the impact of terminal voltages and rate parameters on the state of charge (SOC). Through modeling and simulations, the results show that higher terminal charging voltages lead to a faster SOC increase, making them advantageous for applications requiring rapid charging. However, large values of voltage-sensitive coefficients and energy transfer coefficients were found to have drawbacks, including increased battery degradation, overheating, and wasted energy. Moreover, practical considerations highlighted the trade-off between fast charging and time efficiency, with charging times ranging from 8 to 16 min for different rates and SOC levels. On the discharging side, we found that varying the terminal discharging voltage allowed for controlled discharging rates and adjustments to SOC levels. Lower sensitivity coefficients resulted in more stable voltage during discharging, which is beneficial for applications requiring a steady power supply. However, high discharging rates and sensitivity coefficients led to over-discharging, reducing battery life and causing damage. These new findings could provide valuable insights for optimizing the performance of lithium-ion batteries in various applications.