Energy allocation strategy based on fuzzy control considering optimal decision boundaries of standalone hybrid energy systems

Abstract

Energy management and cost control are inevitable problems that restrict the development of standalone distributed renewable energy systems used in buildings. This paper presents a flexible allocation strategy based on a two-stage fuzzy logic controller to address these problems. Special attention has been paid to the management of stored energy and emergency resource. Decision boundaries are optimised based on actual operating characteristics of units. The fuzzy controller considering decision boundaries is more objective and realizes more accurate real-time energy management with less cost. Sensitivity analysis is conducted for uncertainty factors, which would affect decision boundaries. The effectiveness and advantages of the proposed strategy are verified through a typical hybrid system on an isolated island in the South China Sea. Results indicate that fuzzy controller considering decision boundaries saves 14.15% of the operating cost compared to fuzzy controller without considering decision boundaries, and it saves 20.45% when compared to the fixed priority strategy without flexible allocation. Moreover, its loss of power supply probability is the smallest, which is only 0.72%. A maximum synergy between the power supply and cooling demand is achieved. This novel controller performs better in reliability, economy, and response speed for a real time system. The proposed strategy has a positive effect on practical application of hybrid renewable energy systems for buildings in isolated areas.