Multi-objective Optimization Of Central Air-conditioning

With the rapid development of modern technology,people's demands for life are constantly improving.It has led to a sharp increase in building energy consumption.The central air-conditioning system can provide people with a comfortable working and living environment and play an important role in building.However,because of the complexity of the system and the considerable number of equipment,creating a comfortable environment for people,at the same time,would result in a large amount of energy consumption.Therefore,it is of great significance to study how to effectively balance between the energy-saving and comfort requirement in the operation of central air conditioning to solve the problem of building energy consumption.It is considered that the realization of energy-saving and comfort in the operation of the central air conditioning are two conflicting goals in practice.It is unreasonable to achieve single optimization of central air-conditioning,it should be a multi-objective optimization process.In this thesis,firstly,the application,structure and working principle of the central air-conditioning system are introduced in detail,and the operation energy consumption of the central air-conditioning system and the comfort requirements of the air conditioning room are analyzed.After analyzing the operating characteristics of the system,the total energy consumption model and the comfort evaluation model of the central air-conditioning system are established respectively.The total energy consumption model includes the energy consumption of chiller,chilled water pump,cooling water pump,cooling tower fan and air conditioning unit.The evaluation index PMV,which characterizes the thermal response of human body,and the PPD index,which indicates the degree of dissatisfaction of the thermal environment,are used to describe the comfort model.The physical constraints of the system parameters and the mutual constraints among the parts of the air-conditioning system are given in detail.And based on constraints,the problem model is simplified.Finally,a multi-objective optimization model of central air-conditioning is established with the aim of minimizing the total energy consumption and comfort PPD index of central air-conditioning.In this thesis,the MOPSO algorithm is selected to solve the multi-objective optimization problem of central air-conditioning.In order to avoid the problem of poor diversity and premature solution,the standard MOPSO algorithm is improved before solving the optimization problem.Competitive learning mechanism is introduced in population update to change the way of speed update.It does not need to select individual optimal value and global optimal value,aim to balance between the convergence and diversity of the algorithm.Dynamically adjusting the inertia weight of speed update to balance the global search capability with local search capability of the algorithm.Using non-dominated and crowded distance sorting to update and maintain external file to ensure that they are closer to the real Pareto front and more evenly distributed.Compared with three comparison algorithms,ZDT series test function and IGD evaluation index are selected to verify the algorithm.The results show that the improved algorithm has better overall performance in dealing with multi-objective optimization problems,which verifies the effectiveness and superiority of the improved algorithm.Finally,under the same operating condition,the standard and improved MOPSO algorithm are applied to solve the multi-objective optimization problem of central air-conditioning system at the same time.Simulation results show that the improved algorithm is more effective than the traditional algorithm in dealing with the problem.In order to fully explain the effectiveness of the proposed algorithm for solving problem,different working conditions are chosen for the study.Simulation results show that the algorithm can effectively balance energy-saving with comfort.It can not only meet the requirements of personnel comfort,but also reduce the energy consumption of central air-conditioning system.