Multistage coordinated planning approach for RES-rich microgrids incorporating flexible power balancing unit, V2G scheduling, and hydrogen storage systems

The growing integration of renewable energy sources (RESs) introduces substantial operational challenges, particularly voltage and current unbalance in unbalanced microgrids. This highlights the need for effective compensation strategies, plug-in electric vehicles (PEVs) with vehicle-to-grid (V2G) services, and robust demand response (RDR) programs to mitigate unbalance and boost the hosting capacity (HC) of RES-rich microgrids incorporating hydrogen storage systems (HSSs). Accordingly, this study proposes an innovative compensation strategy employing a flexible power balancing unit (Flex-PBU) that is equipped for independently injecting/absorbing active and reactive power per phase. Smart inverters integrated with RESs provide localized voltage regulation. Moreover, a smart PEV scheduling model featuring V2G services at parking lots is developed, considering energy cost, battery degradation, and an incentive mechanism. This model dynamically aligns charging/discharging activities with forecasted RES availability, demand, battery health, and electricity prices. In addition, an RDR program is proposed to optimally adjust load profiles in response to renewable generation forecasts and price signals by integrating two new adaptive indicators into a unified control framework. To coordinate these technologies, a two-stage planning approach is adopted: in the first stage, the operation of Flex-PBUs, PEVs, and the RDR program is optimized; in the second stage, a multi-objective planning optimization determines the optimal allocation of RESs and seasonal HSSs to minimize voltage and current unbalance, alleviate line congestion, and maximize HC. Simulation results confirm the superiority of the proposed approach, maintaining power quality within standards while achieving a 190% improvement in RES penetration and an 5% reduction in line congestion.