Cascaded fuzzy-PID control using PSO-EP algorithm for Air Source Heat Pumps

Heat pump systems are suitable for most commercial air-conditioning and refrigeration applications. Currently, heat pumps can be regarded as products that would help satisfy the air-conditioning system demands for medium and small sized buildings, thereby reducing electric power demand peaks in summer and achieving save energy in general. This paper presents a cascaded fuzzy-PID (proportionalintegral-derivative) controller for a class of Air Source Heat Pump Systems (ASHPS). The controller´s parameters are offline optimally selected by a combination of the well-known particle swarm optimization (PSO) and evolutionary programming (EP) algorithm. This proposed cascaded fuzzy-PID control structure retains the best merits of both fuzzy control and cascade control structures. The cascade control strategy is shown effective for such a system, and a fuzzy control strategy is shown capable of dealing with systems without accurate models. The performance of the proposed cascaded fuzzy-PID control is compared to that of a pure PID control strategy, and the results reveal that the cascade fuzzy-PID control strategy gives superior performance, reduced transient performance and smaller temperature overshoots.