Equipment Development Of High Power Modular High Frequency Power Supply

Among all kinds of power electronic equipment,high-frequency switching power supply plays an important role as the power supply system.With the continuous development of science and technology,more strict requirements on high-frequency switching power supply have been put forward like volume,high reliability,efficiency,capacity and so on,which also makes high-frequency switching power supply technology innovate and develop towards high frequency,integration,intelligence constantly.Therefore,it is significant to study the high-efficiency and high-reliability power supply for industrial production.Modular equipment has the advantages of easy capacity expansion,small size,large power density,low cost and good versatility.So it is more and more widely used in industrial production and daily life.This paper,based on the two-stage switching power supply,makes a detailed research and parameter design about the pre-PWM rectifier and the post DC-DC converter,the specific work includes the following aspects:Firstly,the development and research status of the high-frequency switching power supply are introduced briefly.Based on the analysis and comparison of different DC-DC structures,the full-bridge topology is then chosen.The topology structure and its working principle for PWM rectifier are analyzed briefly.Then,the mathematical model of PWM rectifier under unbalanced grid voltage is deduced,and the mechanism of the second ripple of DC-side voltage is explained from the point of view of power.For the extraction of positive and negative-sequence components in the unbalanced control system,this paper introduces the working principle adopting the signal-delay method.Then,an active negative-sequence current injection method is used to improve the DC voltage under the two-phase synchronous rotating coordinate system in order to reduce the adverse effects of DC-side fluctuation on the post DC-DC converter.On this basis,the PI parameters of voltage and current control loops are designed.At last,the effectiveness of the control method is verified by the simulation.Secondly,with regard to the DC-DC full-bridge converter,the structure and working principle of phase-shift full-bridge zero-voltage-switching DC-DC converter(ZVS DC-DC)is analyzed in detail,on the basis,a small-signal model of phase-shift full-bridge DC-DC converter is established and an accurate transfer function from control to output inductance current can be obtained as a result.Then,according to the frequency-characteristic analysis method,the control parameters of the dual-closed loop PI control are designed on the basis of the open-loop transfer function,and the performance of the closed-loop feedback control for the whole system is analyzed according to the Potter chart.Then,an input-parallel output-parallel DC-DC converter mode is studied,where an improved automatic current sharing is adopted to improve current sharing characteristics.In order to realize the soft switching technology,the parameters of the resonant inductor and capacitor are designed.At last,the simulation results show the effectiveness of the proposed control strategy.Finally,a rated power of 25kW high-frequency switching power supply prototype is developed,and its detailed design scheme of the main circuit and control system and the corresponding software control subroutine flow chart is given out.Then,the system is debugged and tested on the prototype.The experimental results show that the prototype can output stable and low-ripple DC voltage,which verifies the effectiveness and practical value of the research.