Research On Control Method For Electrode Regulating System Of Electric Arc Furnace

The process of EAF steelmaking is a typical industrial control process with nonlinearity, time-variation and randomness. The control objectives, such as electric power input, reducing its energy consumption and shortening the duration of steelmaking, are mainly completed by electrode regulating system. So the control method of automatic electrode regulator becomes the primary object of the research in EAF control system. But the research of arc model is not profound for long and the electrode is controlled based on linear arc resistance strategy generally, so control effectiveness is not perfect. Therefore, this thesis made an in-depth research on control strategies and controller design for electrode regulating system, based on an new arc model of AC EAF.Based on a great deal of documents related with the EAF, the thesis introduces the process of EAF craft and the components of equipment and summarizes a brief introduction about the current situation and the tendency of development of steel-making process and electrode regulating system of EAF both at home and abroad.Starting from the energy conservation law and related physical theory of arc, and according to the characteristics of the production process of EAF, a time-domain model of the electric arc which is described with nonlinear differential equations is established. The model can reflect the microcosmic properties of the electric arc, and can reflect the time-varying characteristics at different production stages as well.According to the question that parameters in the electric arc model are difficult to determine, the variation range of model parameters is derived from mechanism analysis and then the particle swarm optimization algorithm is applied to estimate the value of model parameters by using the actual data on the basis of the above mentioned variation range. The proposed determination method, compared with the measurements taken from field, is validated.The thesis uses the measured data and the established model to simulate, and applies phase space reconstruction and Lyapunov index method to make analysis qualitatively and quantitatively. It is proved that there is chaos in the electric arc furnace system and the voltage wave form in EAF system is chaotic.The hydraulic system model and the power system model is established. Considering EAF process with the characteristics and properties of the electrode system itself,as well as the existence of chaos in electric arc furnace system, with the entire electrode system model as a controlled object, the thesis purposes a new electrode regulating control method. Chaos electrode compensation controller can effectively eliminate the chaotic phenomenon in the electrode regulation system and achieved the desired control effect.