| The parallel resonant SCR medium frequency power supply plays an important role in forging industry, but the difficulty of its start is still a key factor restraining its performance improvement. In order to solve the low success rate and the not good enough start performance under complex conditions, this paper established a starting model of SCR medium frequency power supply, and proposed an optimization method of starting control parameters. The start model was built based on the start process and the analysis of the load characteristics for power supply. Following works were completed in the paper.Based on the analysis of the starting process of SCR medium frequency power supply, the reasons why the parallel resonant power supply is difficult to start were found out, and measures to improve the ability of starting were correspondingly put forward.The analytic formula in inductor equivalent parameters was derived by the analytic method, the characteristic of equivalent load circuit was analyzed, and the starting process model of SCR medium frequency power supply was established. The step response experiment of open loop and closed loop system was carried out in MATLAB/Simulink circumstance, which verified the correctness of the mathematical model.In order to get better start performance, the start conditions were derived to select the control parameters based on the mathematical model of medium frequency power supply. On account of different loads, the range of rectifier trigger angle under different load decaying factor was deduced and approaches of starting for power supply were provided.A simulation model is established for the medium frequency power supply with initial energy in MATLAB/Simulink simulation circumstance. The simulation experiments were carried out under the conditions that the control parameters were optimized and rectifier angle in different decay factors was selected. The simulation results verify the correctness of the control parameters selection methods and the start strategy.The simulation results show that the proposed mathematical model of medium frequency power and the selection strategy of start control parameters are reasonable, and it has stronger ability to start compared with series-parallel resonant load start method and IGBT auxiliary bridge start method. The study on the mathematical model of the power supply system has a certain reference value for its subsequent research, such as the control problem research and the improvement of power quality for medium frequency power supply. |
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