松村 司郎 中部電力(株), 電力技術研究所, 研究主査
OGATA Kazuya Nagoya University, Faculty of Engineering, Assistant Professor, 工学研究科, 講師 (30252258)
周 超俊 名古屋大学, 工学部, 助手 (70262863)
MATSUMURA Siro Electric Power Research and Development Center, Chubu Electric Power Co., Inc.
A simulator has been developed for the purpose of studying of the sliding pressure operation method for thermal power plants by means of MMS (Modular Modeling System). There are a lot of modules supplied by MMS,which are developed based on the laws of thermodynamics. These modules are boiler, superheater, attemperator, turbine, economizer, piper, condenser, deaerator, feedwater heater, and so on. Two hundreds of MMS modules are used to develop the simulator together with the data collected from real plant and manufactory.
Several studies have been done in order to validate the accuracy of the developed simulator. It is shown that the results of the simulator at the rated load are agreed with that of the real plant well. Although the simulator is ahown to be stable by simulation examples, there still exist some problems in calculation aspects. The simulator is 'stiff' in calculation, because there are very fast modes and very slow modes. The fast modes originate from the turbine, and slo
w modes originate from the boiler and reheater. The simulation costs amount of CPU time if demand of load is changed largely. The calculating stiffness makes it difficult for us to validate the dynamic accuracy of the simulator. A simlified simulator has then been developed in order to improve the calculating efficiency.
After studying the current PI based control systems of the real plant, we have developed a new control system structure which is composed of a FF (feedforward) control action from the demands of load and pressure of main steam to fuel flow rate control system and temperature control of main steam. The proposed FF control can be plugged in the current PI based control systems. In order to design the FF controller, a time varying model for boiler plant is developed. This model is interpolated by several linearized models of the boiler plant at several levels of demand of load and pressure. These linearized models are identified by stimulating the simulator with PRBS (pseudo random binary sequence). According to this time varying model, a FF controller that is gain scheduled by demands of load and pressure is developed. A lot of simulation studies have been carried out for cases of small step change of demand of load and pressure and large ramp change of demand of load and pressure. The simulation results are satisfactory. The controlled error of main steam temperature has been reduced to 50% comparing with that of without FF controller.