Research On High-efficiency And High-Power-Density Power Supply

As a kind of special power supply, the high-voltage converter is applied in many fields,including High-Power-Microwave(HPM) System, Active Denial System, X-Ray machine,Electron Beam Welding machine, High Energy Physics and Controlled Fusion Reactor. With some research results used outside the laboratory and with the trend of system miniaturization, the demands for high voltage power supply are no longer limited to the output performances, the efficiency, electromagnetic compatibility, reliability and size are also needed to be considered. In view of the drawbacks of current high voltage power supply when used to meet the above comprehensive demands, on the base of fully investigation to scientific and technical literature, in this paper, research is carried out around the input power quality, efficiency and power density of high voltage charging and DC power supply.The main contents of this paper are below:In this paper, capacitor charging power supply is studied firstly. With the analysis of the target of constant input power and constant output current and based on the feature that the resonant circuit absorbs energy in the first half of resonant cycle and release the excess energy in the latter half cycle under discontinuous mode, a new topology and corresponding control strategy of this kind of CCPS with auxiliary energy storage capacitor are proposed.Analysises of the topology and control strategy are carried out and the corresponding control parameter is deduced. Circuit simulation and experiment are conducted, and the results show that during the period of charging with constant output current, the input power of the proposed CCPS is basically stable and the value of it is about half of the peak value in traditional CCPS. With this way, it can not only avoid series voltage distortion under high repetition condition, but also can reduce the power level of power generator and distribution part in HPM system. It contributes to high efficiency and high power density in system level.In addition, the feasibility of this topology used in uninterruptible-power-supply(UPS)system is discussed.The following chapters focus on the relevant issues in the AC-link route. The third chapter studies the control of input current of 30 AC-link based converter. Firstly, the distortion of the input current in the experiment is classified and analyzed, and solutions to modify the control strategy and the algorithm based on the trend of current distortion are presented. Secondly, the phase-shift control of input current is studied to compensate the phase shift caused by the input filter and improve the input PF at a low output power condition. Based on the analysis of input current control in principle, the modified method to the original control scheme is introduced to realize the phase-shift function. Circuit simulation and experiment are conducted to show the feasibility. Besides, the above two modified methods can be used as the basis for the following research. In the fourth chapter,the high voltage power supply based on AC-link and discontinuous current mode of series resonant is studied. With state diagram method, the characteristics of resonant current pulse are analyzed and the theoretical control parameters are derived. According to the relations of the average current of single pulse with the grid phase and the output voltage, the theoretical evidence of the linear frequency modulation scheme is found and closed-loop control system including feed-forward and feed-back method is set up. Circuit simulation and experiment are conducted for verification of feasibility. The combination of the discontinuous mode with AC-link route is used as a transition scheme to realize good performance (high PF and low THDi) at input side and high total efficiency in the high voltage power converter.In the following chapters, the high voltage power supply based on AC-link and continuous current mode of series resonant is studied to further improve the power density level. The working principles of AC-link converter with the above and below resonance mode and combined frequency and phase-shift control method are explained. With the energy conservation constraints, high input power factor constraints, stable oscillation constraints and output current conditions, the complex resonant process with 3 related time parameters are deduced. The applicable conditions and merits and demerits of these two types of resonant mode are analyzed. The switch commutation for the complex working process is introduced. On the base of analyzing the series-resonant circuit and working mode,the closed-loop control method is given. Optimal design for the AC-link based converter with 100kW output power and 50kV output voltage is made. Circuit simulation and experiment are conducted, and the results show that the voltage ripple factor is less than 1%,the input power factor is 0.99,the total efficiency is 95% and the power density is 1.17W/cm~3.