Two-stage coordinated planning of hybrid BESS–hydrogen storage incorporating unbalance compensation and dynamic demand response for renewable-rich microgrids

Abstract

The increasing integration of renewable energy sources (RESs) into unbalanced microgrids introduces operational challenges, including voltage and current unbalance, feeder overloading, and reduced system performance. Energy storage systems (ESSs), such as battery energy storage systems (BESSs) and hydrogen storage systems (HSSs), can support reliable RES integration and enhance operational flexibility. This article proposes a coordinated two-stage planning framework for the optimal placement and sizing of RESs, BESSs, and seasonal HSSs to mitigate unbalance, reduce feeder loading, and maximize hosting capacity (HC). The framework incorporates a hybrid unbalance compensation strategy and a dynamic demand-response (DDR) program. The compensation strategy combines a flexible phase-power-balancing unit (Flex-PBU) with coordinated smart inverter control. The Flex-PBU enables independent phase-wise active and reactive power regulation while considering converter ramp-rate limits, degradation costs, and unbalance levels. Smart inverters associated with RESs and ESSs provide additional local voltage support. The DDR program integrates electricity tariffs, carbon pricing, and RES variability to improve demand-side flexibility. In the first stage, the operation of the Flex-PBU and DDR program is optimized using day-ahead forecasts of demand and electricity prices. In the second stage, a multi-objective optimization model determines the optimal locations and capacities of system assets. Simulation results demonstrate the effectiveness of the proposed approach, maintaining voltage and current unbalance within standard limits while achieving a 106% increase in RES integration and an 11% reduction in feeder overloading.