Research On Key Technology Of Digital Medium Frequency Induction Heating Power Supply

Induction heating,as a non-contact heating technology,is widely used in the field of industrial heat treatment,such as diathermy,smelting,quenching,and fiber pulling.By using the principle of electromagnetic coupling to induce eddy current heating on the heated material,it can complete the Most industrial heat treatment requirements.With the demand for high-power,digital,and high-precision control of power supply equipment,the research on control technologies such as frequency tracking and power adjustment of induction heating power supplies has important practical significance.Therefore,this article focuses on the following researches on key technologies such as digital intermediate frequency induction heating power supply frequency tracking and power adjustment.First,take the topology of induction heating power supply as the research object,compare and analyze the working characteristics of the two topological structures of series and parallel resonance,and use the voltage-type series resonance circuit as the main circuit of the power inverter.And on this basis,the load tank circuit characteristics are analyzed,and the third-order LLC series resonant load structure to prevent overcurrent is determined.In view of the shortcomings of low load quality factor of LLC series resonant load tank circuit in traditional parameter calculations,the ratio of the two inductances of the load tank circuit is calculated according to the rated maximum output power of the power supply to determine the range of quality factor Q,and the parameter calculation of the maximum quality factor is proposed method.Secondly,taking the intermediate frequency induction heating power supply control system as the research object,a compound control strategy based on fuzzy-PID and quasi-PR dual controllers based on different control precisions is proposed.Aiming at the problem of poor reliability of frequency tracking of traditional phase-locked loop and improving frequency tracking accuracy,a mathematical model of phase-locked loop is established,and a quasi-PR controller is introduced to design a digital frequency tracking closed-loop control system,which combines the LLC series resonant load tank in the inverter main circuit.The circuit uses capacitor voltage and inverter output voltage as the control variables of frequency tracking,which improves the tracking accuracy and eliminates the steady-state error of frequency tracking.The simulation results show that the digital phase-locked loop based on the quasi-PR controller can quickly track the frequency change caused by the load change,make the power supply work in the resonant state,and the DPLL system enters the locked state,and has the speed and accuracy of frequency tracking.Certain superiority.In order to quickly adjust the output power of the induction heating power supply,an uncontrolled rectifier circuit BUCK chopper circuit is used to achieve the power adjustment of the power supply.A closed-loop control strategy combining fuzzy algorithm and PID controller is proposed.The real-time power of the load is first compared with the PID controller.The given power of the system is compared,and the change of the error value is analyzed through the fuzzy algorithm,and then the proportional and integral coefficients of the PID controller are accurately adjusted according to different working conditions by the formulated fuzzy rule table and rule statement,so as to reduce the controller.The purpose of overshoot is to speed up the dynamic response speed.The simulation results show that the closed-loop power regulation control strategy based on the fuzzy-PID controller is feasible,and it effectively improves the power regulation speed and the stability of the output power.Finally,a simulation model of a digital intermediate frequency induction heating power supply is built in the Matlab/Simulink simulation platform,which includes closed-loop control systems such as frequency tracking,power adjustment,and the overall topology of the power supply.The simulation results show that the power supply control system can effectively find the resonance point of the load circuit,and quickly adjust the output power and operating frequency in real time to achieve the maximum output power of the power supply.