Evaluation of Grid-Connected Micro-Grid Operational Strategies

Abstract

Abstract This study investigates the operational performances of a grid-connected microgrid with integrated solar photovoltaic and battery energy storage. The study is based upon the techno-economic specifications and theoretical performance of the distributed energy resource and storage systems, as well as on measured consumer load data and electrical utility retail and distribution data for representative residential and commercial loads for the city of Vasteras, Sweden. The open-source Matlab®-based simulation tool, OptiCE, is used for performing simulations and optimization. To support the attainment of one of the objectives, peak shaving of the consumer load, a battery operational strategy algorithm has been developed to balance peak shaving and PV self-consumption. Comparisons among three types of battery, lead-acid, lithium-ion and vanadium-redox flow, are also performed. A 117 kWp photovoltaic system paired with a lithium-ion battery of 41.1 kWh capacity is the optimal solution found for the considered commercial load. The calculated battery capacity represents the best trade-off for the set multi-objective optimization problem. The simulation of this system predicts the possibility to shave the customer load profile peaks up to 20% for the month of April. The corresponding self-consumption ratio is 88%. Differences in the relationship between the load profiles and the system performance have been qualitatively noted. Furthermore, the simulation results for lead-acid, lithium-ion and vanadium-redox flow battery systems reveal that lithium-ion batteries delivers the best trade-off between total annualized cost and peak shaving performance for both residential and commercial applications.