Optimal Coordinated Scheduling of Grid-Connected Hybrid AC/DC Microgrid for Minimizing Battery Degradation Costs and Interlink Converter Stress Levels

The interlink converter (ILC), functioning as the tie-link between sub-grids, forms the backbone of the hybrid AC/DC microgrids (HMGs). The stress of the ILC encompasses the wear it undergoes due to power exchange between subgrids and increases in the junction temperature of the switches. This stress leads to the degradation of the converter over time, leading to reduced lifespan. Therefore, it is imperative to consider the stress level of the ILC in the optimal scheduling of the HMG. Additionally, battery energy storage systems (BESS) play a crucial role in the economic operation of HMGs by charging at low energy prices and discharging at high energy prices. However, existing HMG scheduling systems have overlooked the stress reduction of the ILC in the scheduling systems that affect HMG operations technically and economically. This paper proposes a risk-constrained stochastic distributed scheduling system to simultaneously minimize the stress level of the ILC, the degradation cost of the BESS due to its capacity fade, and the purchasing power expenses from the grid. A new methodology is introduced to calculate the stress levels on the ILC using the Arrhenius equation. Real data is utilized to validate the performance of the proposed scheduling system. Various detailed comparisons are conducted to demonstrate the superiority of the proposed strategy over existing approaches.