Cascaded fuzzy control for air source heat pumps

Air source heat pump systems (ASHPS) are particularly useful for most commercial air-conditioning and refrigeration applications. Currently, such systems can be regarded as products that satisfy the air-conditioning system demands for small and medium sized buildings, thereby reducing electric power demand peaks in summer and saving electric energy in general. To accomplish out temperature control of ASHPS, this paper presents a cascaded fuzzy control strategy which retains the merits of both fuzzy control and cascade control structures. The cascade fuzzy control strategy is designed without accurate models of ASHPS, and it is shown effective and powerful in achieving temperature tracking. Simulation results are conducted to compare the proposed cascaded fuzzy control with a cascaded PI (proportional and integral) control strategy, and the results reveal that the cascade fuzzy control strategy gives superior performance, reduced reaction time and smaller temperature overshoots.