The Application Of Supervisory Predictive Control In Organic Rankine Cycle (ORC) System

Low temperature waste heat resources exist widely in industrial processes, and the amount is huge. The effective utilization of waste heat has huge economic and social benefits. In low temperature waste heat power generation field, Organic Rankine Cycle system receive considerable attention because of its characteristics of high efficiency, low requirements for equipment and using organic fluid. In ORC system, As the key element of system, evaporator and scroll expander has a direct relationship with all the system. So, the paper has conducted deep study on their mathematical models and control algorithm.Based on deep research on scroll expander’s working process, the paper establishes dynamic mathematical model of scroll expander by making study on the scroll expander leakage model in reference, and according to the principle of governing system, establishes scroll expander electro hydraulic governing system. Scroll expander electro hydraulic governing system includes nonlinearities behavior and uncertainties. To resolve this problem, single variable supervisory predictive control is used to control the governing system. Supervisory predictive control (SPC) based on GPC theory is an effective optimization control algorithm for complex system which can be realized by adding a supervisory optimal level without modifying the regulatory level. To decrease the time spent on optimization, the improved algorithm of SPC is studied. Single variable improved supervisory predictive control is studied. And it is applied in scroll expander governing system. Comparisons with the Generalized Predictive Control are made. The method has good control effect and improves the governing system’s performance effectively. And Simulation results show excellent tracking results.Evaporator, as the energy exchange device, plays an important role in ORC waste heat power generation system. It has obvious change by the influence of random changes in heat sources and other factors. Based on the superiority of supervisory predictive control in scroll expander governing system, the paper realizes multvariablev supervisory predictive control on evaporator. The results show effectiveness of the algorithm and the improved supervisory predictive control has better control effect.