Research on Two-Stage Low Power Inverter
|School||Nanjing University of Aeronautics and Astronautics|
|Course||Power Electronics and Power Drives|
|Keywords||DC/DC DC/AC Flyback Converter Dual Buck Inverter Peak Current Control Loss Analysis Close Loop Design Parasitic Parameters|
Two-stage low power Aeronautical Static Inverter (ASI) is being researched in this thesis. Based on the comprehensive investigation of different strategies, and for the purpose of improving overall efficiency and realizing low profile, the first stage of ASI employs flyback converter, which is simple and easy to get multi-output voltages, and the second-stage selects the dual buck inverter (DBI), which is highlighted by high efficiency and high reliability.The operation principles and characteristics of basic flyback converter were first presented. Then for the requirements of the application, several prototypes were developed, and they were single-switch flyback converter and dual-switch flyback converter, both operating in both the discontinuous current mode (DCM) and the continuous current mode (CCM). Loss analyses of these converters were performed with the help of MathCAD software, and through comparison, it revealed that the efficiency of DCM dual-switch flyback converter was highest, and that of CCM single-switch flyback converter was lowest. The experimental results verify the correctness of the theoretical analysis. It also shows that the proper design of transformer is very critical to the performance improvement of flyback converter in high-voltage, high-frequency applications. As a result, the effects of parasitic winding capacitance on the operations of high-voltage, high-frequency flyback converter were analysed and the influence of winding strategy on winding capacitance was studied. Then some suppression methods to the light-load unsteady problem were proposed and they were verified by experimental results. Moreover, the modeling and close-loop design of flyback converter under DCM and CCM modes are discussed, and some initial research on cross regulation in multi-output flyback converters was also given.Compared to conventional half-bridge inverter, dual buck inverter (DBI) overcomes the short-through problem, and can choose the power switches and the power doides separately, and realizes the optimum design of power devices, with the result of higher overall efficiency and high reliability. With the introduction of the working principle of DBI, a 100VA prototype was developed. And suitable for low power application, the current detecting element employs resistance instead of current LEM and it features simple, low cost, small size and light weight. Simulation and experimental results verify the feasibility of the proposed current detecting method. At last, the two-stage ASI is tested, and the experimental results show that the developed ASI has high efficiency and high stability.