Grid-connected micro-grid operational strategy evaluation : Investigation of how microgrid load configurations, battery energy storage system type and control can support system specification
Abstract: Operational performance of grid-connected microgrid with integrated solar photovoltaic (PV) electricity production and battery energy storage (BES) is investigated. These distributed energy resources (DERs) have the potential to reduce conventionally produced electrical power and contribute to reduction of greenhouse gas emissions. This investigation is based upon the DER’s techno-economic specifications and theoretical performance, consumer load data and electrical utility retail and distribution data. Available literature provides the basis for DER specification and performance. Actual consumer load profile data is available for residential and commercial consumer sector customers. The electrical utility data is obtained from Mälarenergi, AB. The aim is to investigate how to use simulations to specify a grid connected microgrid with DERs (PV production and a BES system) for two consumer sectors considering a range of objectives. An open-source, MATLAB-based simulation tool called Opti-CE has successfully been utilized. This package employs a genetic algorithm for multi-objective optimization. To support attainment of one of the objectives, peak shaving of the consumer load, a battery operational strategy algorithm has been developed for the simulation. With respect to balancing peak shaving and self-consumption one of the simulations supports specification of a commercial sector application with 117 kWp PV power rating paired with a lithium ion battery with 41.1 kWh capacity. The simulation of this system predicts the possibility to shave the customer load profile peaks for the month of April by 20%. The corresponding self-consumption ratio is 88%. Differences in the relationship between the load profiles and the system performance have been qualitatively noted. Furthermore, simulation results for lead-acid, lithium-ion and vanadium-redox flow battery systems are compared to reveal that lithium ion delivers the best balance between total annualized cost and peak shaving performance for both residential and commercial applications.
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