Research On Double-closed Loop Control IGBT Induction Heating Power

As a new heating mode, induction heating has the advantages of energy saving, environmental protection and security etc. With developing rapidly in recent years, it is widely applied in heat treatment of metals and other fields. The development level of induction heating power supply is closely related to semiconductor power device. IGBT (Insulated Gate Bipolar Transistor) is the main switch power device in the power electronics. Due to the fast switching speed and low dropout voltage, it is widely used in power electronic devices. It is very valuable to research on the application of IGBT in the induction heating power.Taking10kW/20kHz induction heating power as an example, in view of intelligent driving and large power consumption of IGBT, the paper was carried out a research in the aspects of frequency automatic tracking, power closed-loop control and soft switch technology. First, based on DSP a design scheme of perceptual phase-shifting PWM&PFM was proposed. The main loop consists of three-phase uncontrolled rectifier, IGBT full bridge inverter and series resonance load. Second, combining PID (Proportional Integral Differential) controller with DPLL (Digital Phase-Locked Loop), the double closed-loop control strategy was adopted. The simulation modeling of induction heating power system was realized by SIMULINK. Third, on the basis of simulation, the driving circuit with the core of SKHI22AH4R module was implemented. Finally, through the signal acquisition of the load output voltage and current, modular design including PWM module, PID module and DPLL module is adopted by DSP. The software programming control is realized. The experimental platform and the integrated debugging are completed.The simulation is analyzed in the condition of open and closed loop. The results of closed loop system indicate that the time reaching constant power output is200ns. After6to7cycles, phase locking and frequency automatic tracking can be realized, and power factor is approximate to0.99. Moreover, there is no periodic jump phenomenon. Through integrated debugging, PWM pulse of which width and frequency are adjustable is generated by the DSP. It has a dead zone of3.3μs. The driving control voltage (+15V/-7V) of the IGBT is acquired. Through programming, the digital frequency tracking and ZVS soft switch technology have been realized, reducing the IGBT switch consumption.Experimental and simulation results indicate that the phase-locked frequency automatic tracking and power control are implemented. The power factor of the induction heating power supply is improved, and the high power consumption of IGBT in the process of work is solved. The dynamic characteristics and stability control of the induction heating system are improved. Meanwhile, feasibility and effectiveness of the scheme are verified.