Research On Control System Of The Series Mediate Frequency Power Based On DSP

This paper analyses the base structure and principle of the induction heating power supply,and comparing the merits and demerits of the parallel resonant medium frequency power with the power connected in series, this paper chose finally the series resonant medium frequency power supply as the research object. The rectifier circuit of Mid-frequency Source used the diode not-controlled rectification and the inverter circuit adopted the topological structure of the IGBT the single-phase all Bridge.For the shortage of the harmonic distortion of output voltage produced by traditional control strategy in large, this paper emphatically put forward to the innovation of reducing the harmonic distortion of output voltage by using SPWM control strategy in the induction heating power supply. And the double closed-loop system is simulated by MATLAB, the result of simulation experiment verify the feasibility of this project. On the basis of the theoretical analysis, the digital-control system of the medium-frequency induction heating power supply is designed based on TMS320F28335 by researching the digital control of power system, and the digital phase-locked loop(DPLL) is designed to track the load frequency for maximizing the machine efficiency. The control method applied to the double closed-loop control strategy. Power outer ring can be stable output power, and the frequency inner ring make the phase of voltage and current consistent. In addition, the driving circuit of power tube and other related protection circuit are designed.This experiment writes software and debugs hardware according to the unipolar SPWM control algorithm as the core of DSP program by a 5kW series resonant induction heating power experimental prototype. The test result is consistent with theoretical analysis and simulation experiment, so the SPWM control strategy in combination with DPLL using in the medium frequency heating power supply is verified well feasible. The experiment shows that this control strategy applied to the series resonant induction heating power supply makes the wave of output voltage close to sine wave for improving the performance of power quality and power supply.