A Compensation Strategy for Mitigating Intermittencies Within a PV Powered Microgrid Using a Hybrid Multilevel Energy Storage System

Solar PV intermittencies due to passing clouds with high ramp rates occurring for a short time produce a significant challenge to grid voltage and frequency regulations of a PV-rich microgrid. To compensate for these high ramp rates, battery and/or supercapacitors (SCs) are commonly employed using the control strategy based on a moving average (MA) or low pass filter (LPF). However, the traditional MA and LPF schemes suffer from memory and time lag effects, resulting in the need for increased storage size. To address these issues, this paper describes the design and implementation of a generic ramp-rate-based compensation strategy for smoothing the solar power output and meeting rapid load demands in grid-interactive microgrids using a hybrid multilevel storage system, consisting of high-capacity buffer storage such as battery system and hydrogen storage comprising a proton exchange membrane electrolyzer and a fuel cell, and short-term cache storage such as supercapacitors, integrated in the DC link of the power converter. This hybrid multilevel modular storage system is required to rapidly control fluctuations in solar PV outputs and load demands over a wide range of time scales and regulate the voltage at the point of common coupling (PCC). The proposed compensation strategy is modeled and validated through simulations using a measured 24-h solar irradiance profile applied to a 100-kW grid-interactive PV-dominated microgrid system.