Research On Induction Heating Power Supply For Steel-plastic Pipe Heating

Plastic-steel-plastic composite pipe(steel-plastic pipe)as a widely used plastic pipe in industry,with the advantages of corrosion resistance,long service life,has been widely used in water supply,communication protection,chemical industry,and other fields.Induction heating has become the first choice for steel-plastic pipe hot melt welding because of its advantages of easy temperature control.The commonly used temperature control method in steel-plastic pipe hot melt welding process is discontinuous constant power control,which may affect the effect of steel-plastic pipe hot melt welding because the temperature of this method reaches the stable stage for a long time.In addition,the pulse frequency modulation(PFM)method commonly used for low power range heating load pipe power inverter efficiency is low.In order to shorten the time of temperature regulation and improve the quality of steel-plastic pipe hot melt welding,the model reference adaptive control is applied to the induction heating system,and in order to improve the efficiency of the power inverter in the low power stage,an asymmetric frequency modulation(AFM)method is studied.Firstly,the AFM power regulation method is introduced in detail,and it is analyzed that different working modes of the inverter can output different levels of power under this power regulation method.According to the heating power range of the pipe,different load pipe are corresponding to different working modes of the inverter.Then,the principle of the model reference adaptive control is introduced,and the key to the design of the adaptive control system is to establish an ideal temperature model and design the adaptive control law of the system.Firstly,the mechanism modeling method was used to determine the structure of the system model,then the least square method was applied to the parameter identification of the experimental modeling method to obtain the final temperature model of the system,and the local parameter optimization method was used to design the adaptive control law of the system,and the stability of the system was verified.Finally,the correctness and feasibility of the scheme are verified by simulation and experiment.