Simulation Of The Dynamic Performance And Research On The Control And Optimization For The District Heating System

With the rapid development of the urbanization, District Heating System has play an even more important role in our life. Many researchers have done much for the DHS.Dynamic models of district heating systems are essential for simulation and control design. Subsystem models have to be developed for the heat source, pipelines, heat exchangers, and pump. The pipe can be regarded as one dimension and the equations for the heat transfer and flow of the pipe are evolved and resolved. The pump models adopt the variable frequency pump and the math model is deduced and resolved. The node equation is also constructed and the dynamic performance of the node is also studied. The math model of the heat exchanger is established and the dynamic response is also settled.The subsystems constitute the whole DHS simulation system. The variable flow and the heat transfer conditions are researched in the system. The impact of the leak of the node is also discussed. When the pump frequency changes or the flux in some pipe changes, the movement trend of other pipes is alike in the gross. When the frequency decreased, the temperature of the cycle water firstly rises and then fall down. Mean while the temperature of the nodes share the same trend. When the resistance is reduced in one pipe, the flux of others soars up.. the return water temperature increases and the supply water temperature of heat consumer also increased. When the leak of some node happened, the flux of out of pump get a raise and the temperature gets down if the temperature and the flux of heat source keep constant. The flow and the heat transfer far from leak point experience little influence. The flux of pipe near to the leak point decreased and the return water of heat exchanger and the supply water of the heat consumer decreased also when the pipe is in the front of leak point. When in the behind, the flux increased and the temperature also rise.To implement the automatic control of the branches of the district heating system, the two-degree-of-freedom PID controller is developed in this paper and the parameters are optimized too. MATLAB/SIMULINK is applied to simulate the new PID controller. Compared with the traditional PID, the new controller is more accurate and stable. With considering the thermal loss and the leak loss, the primary district heating system energy consumption equation is set up and the three regulation modes for the district heating system are compared for economic analysis. The GA is used to optimize and solve the equation to obtain the optimized supply temperature and supply water flow in different operation conditions.