Research On Control System Of Digital Induction Heating Power-supply

With its advantages of low energy consumption,high heating efficiency,clean and no pollution,induction heating power supply has been widely used in machinery manufacture,metal heat treatment,petrochemical industry and domestic heating,and other fields.According to the disadvantages of traditional induction heating power supply,for example,complex structure,low ability of anti-interference,can not automatic control,this paper designed an adjustable frequency digital induction heating power supply.The frequency can be regulated from 800 Hz to 40 kHz by setting parameters in the program.The paper mainly made a deep research on digital phase locked loop(DPLL)technology and compound power regulation technology,also made a electromagnetic field and temperature field simulation of steel strand induction heating model.The main circuit construction of the power supply used AC-DC-AC transformation,designed LC parallel resonant loading.TMS320F28335 is the core of the control circuit,designed sampling circuit,driving circuit,protecting circuit,as well as its corresponding soft-programs.The new DPLL designed could implement the function that converter's switch frequency followed the frequency of loading.The function of DPLL implemented completely by programming.And it could implemented frequency tracking of different range by modifying corresponding parameter conveniently.In order to guarantee the stability of output power,this paper designed a parallel compound controller which its weight could be regulated continuously.And this controller gave consideration to the advantages of adaptive neural fuzzy controller and PID controller,depending on the error of power to distribute the weight of two parallel controllers.The simulation result showed that the compound algorithm have good dynamic control property and strong anti-interference property.The compound controller could obtain accurately and stably control effect for the power-supply.Then this paper made a series of experiments on a prototype,and measured rectification triggering pulse,rectification voltage waveform,IGBT driving waveform and loading resonant waveform,verified the correctness of theoretical analysis and the feasibility of scheme design.With the example of steel strand heating,the paper used finite element analysis method based on ANSYS made a calculation of electromagnetic field and temperature field for steel strand induction heating model.By analyzing the distribution of electromagnetic field and eddy field,we had a intuitive recognition for the electromagnetic field theory of induction heating power-supply.And in the condition of specific current density andheating frequency,by analyzing the distribution of temperature,we obtained the best time of steel strand heating.