| High power medium frequency induction heating power supply is widely used in smelting,diathermy,quenching and many other fields.Advanced control technology is the guarantee of high-efficiency and stable operation of induction heating power supply system.Therefore,in order to meet the needs of industrial high-power rapid heating,this thesis takes the series harmonic medium frequency induction heating power supply as the research object,focusing on fast frequency tracking and fast power regulation.The research on control technology has theoretical significance and application value.At present,in the high-power and high-frequency state,there are some problems in the medium frequency induction heating power supply,for example,the fast heating speed of load easily leads to the too fast frequency change,the working frequency can not track the natural frequency in time,the working state of the power supply is not stable,and the adjustment response time is long.Based on the principle of induction heating power supply,this thesis analyzes the structure and working characteristics of series resonant and parallel resonant medium frequency induction heating power supply.According to the parameter requirements and working conditions of the power supply,a series resonant inverter topology suitable for fast heating of workpieces is given.In order to solve the problem that the frequency of high-power medium frequency induction heating power supply changes too fast with the increase of temperature,which causes the system instability,an improved frequency tracking control strategy is proposed based on the traditional frequency tracking control technology.The improved frequency tracking control strategy adds a fuzzy-PI controller to the phase-locked link,and divides the frequency tracking into two stages of “coarse tuning” and “fine tuning”.Combined with their respective control advantages,different appropriate control means are adopted in different stages.Comparing the real-time phase difference with the given threshold value,the fuzzy rule is used to “coarse tune” the phase difference when it is greater than the threshold value,and the PI control algorithm is used to “fine tune” the phase difference when it is less than or equal to the threshold value,so as to shorten the total frequency tracking time,realize fast frequency tracking and improve the system response speed.The fast power regulation control technology adopts the phase-shift PWM power control mode,the voltage and current double closed-loop control strategy,the proportional integral controller as the feedback controller,and the integral separation algorithm to solve the integral saturation problem,so as to realize the stable operation of the system.The simulation model is built in MATLAB/Siumlink,and the algorithm is used to realize the digital control of high-power if induction heating power supply,which shortens the adjustment time of frequency and power.The simulation results show that the improved frequency tracking control strategy and power control strategy are fast and effective,and provide a theoretical basis for the development of high-power induction heating power control technology. |
