Research On Modeling Of DSG Trough Solar Collector System And Predictive Control

Parabolic trough DSG (Direct Steam Generation) system, using water as the working fluid, is regarded as the future development direction of solar-thermal power generation. Precise calculation and improvement of solar field efficiency, to ensure the stability of control are the technical challenges for DSG system. The foundation of realizing above research goals are to establish the mathematic models of solar field and heat-transfer, to research its operational mechanism, control methods and energy utilization strategies. Therefore, taking trough collectors as the main research object, this article studies the DSG thermal process model and control strategies for the outlet steam temperature by principle analysis, mathematical modeling and simulation. The main results are shown as follows:(1) The optical loss of solar field is researched. Optical loss of trough collector is subdivided into optical loss of reflector and optical loss of collector tube. Then, for the optical loss of distribution, this article does simulation calculation on cosine efficiency, mutual occlusion between rows and the loss at the end of the collectors in different areas and seasons. Two steam complementary schemes are also put forward. The above research presents some technique data for the solar field design and its performance improvement.(2) Steady-state heat-transfer model of DSG collector is developed with thermodynamic principle. Using infinitesimal method in the process of solving the model, this article has carried on the coupling solution for the temperature of the outer wall, heat transfer coefficient, water temperature, dryness and other parameters. By simulating analysis, the proposed model is verified by the comparison between the experiment data and simulation analysis. Then the relationship between the outlet steam temperature and the direct normal insolation (DNI), fluid mass flow is investigated.(3) Dynamic model of DSG collector is set up. It presents the dynamic response of the working fluid temperature under the step disturbance of DNI and fluid mass flow. In addition, the transfer function of the working fluid temperature as fluid mass flow disturbs obtained by two-point method is given. The approximation function has high accuracy, which lays the foundation for the research of the control strategy of the outlet steam temperature.(4) The generalized predictive control (GPC) based on dynamic model of DSG collector is studied in depth. In order to improve the shortcoming of local minimum of basic PSO algorithm, this article introduces the dynamic particle swarm D-SWPSO algorithm based on any initial small world neighborhood firstly. Simulation analysis shows that the D-SWPSO algorithm owns higher search efficiency and accuracy than basic PSO algorithm. The D-SWPSO algorithm is more suitable for the set-point tracking and optimization solution of GPC whose controlled objects always have great inertia and pure time-delay. Then this article makes the transfer function of the working fluid temperature as fluid mass flow disturbs and the transfer function model of the spray desuperheating system as the controlled object to simulate with proposed algorithms. Simulation results prove that the algorithm has better performance than traditional PID control algorithm, so it can provide reference for outlet steam temperature control of actual DSG trough collector.