Intelligent Controller Design For Waste Heat Recovery VRV Based On Embedded System

Waste Heat Recovery Variable Refrigerant Volume air-conditioning is a new type of air conditioning system that integrates condensation heat recovery technology and VRV airconditioning’s variable refrigerant flow technology.The condensing heat recovery technology recovers and reuses the waste heat emitted during the operation of VRV air conditioning,while the VRV(Variable Refrigerant Volume)air-conditioning system combines multiple units,variable frequency,energy-saving,and other technologies in one.It is widely used in residential buildings because of its low energy consumption and stable working performance.However,the addition of condensing heat recovery technology can increase the uncertainty of VRV air-conditioning systems and create difficulties for the stable control of the system.Therefore,it is important to study the control strategy applicable to the waste heat recovery VRV air-conditioning,a new type of air conditioning system.For this purpose,the following work is done in this thesis.First,the structure and cooling cycle principle of the waste heat recovery VRV airconditioning system and the operation mechanism of the main components are analyzed,and an engineering model of the air conditioning system is established.For the characteristics of large room air supply temperature perturbation,an indoor unit controller combining the modified differential evolution(MDE)algorithm and the cascade PID control method is designed,and the MDE algorithm is used to rectify the parameters of the primary and secondary PID controllers to achieve accurate control of the room temperature.Second,for the refrigeration compressor suction pressure disturbance parameters that are complex with nonlinear,time-varying,large hysteresis,and other characteristics,the refrigeration machine controller is designed with a combination of variable-domain fuzzy PID and fuzzy feedforward compensator.The variable-domain fuzzy PID control is based on the error of suction pressure and its rate of change as input,and the PID controller parameters are adjusted online to control the refrigeration compressor suction pressure and thus realize the refrigeration capacity control.Meanwhile,the fuzzy feedforward compensator is designed to correct the refrigeration compressor frequency in advance for the influence of the change of water temperature of the plate heat exchanger on the system stability in the waste heat recovery VRV air-conditioning.It is verified through simulation that the cascade PID controller based on the MDE algorithm can effectively reduce the influence on room temperature in case of fluctuation of supply air temperature,and it is also shown that the combination of variable-domain fuzzy PID and fuzzy feedforward compensator improves the influence of heat recovery water temperature variation on the cooling capacity.Then,based on the control strategy identified in the above study,an intelligent controller for waste heat recovery VRV air-conditioning was developed based on the embedded system.Completed the hardware circuit and made the PCB board.Developed the embedded controller driver program,indoor unit control program,and chiller control program.Finally,a comprehensive energy utilization experiment platform was built with the physical model of the laboratory,and the embedded controller experimented on the experiment platform.The experimental results show that the designed embedded controller operates stably and the control algorithm achieves the expected effect,which can meet the actual control demand of waste heat recovery VRV air-conditioning.