Research On A Novel Type Of Passive Soft-Switching Three-Phase PWM Inverters

In recent years, power electronic devices are developing toward miniaturization and lightening. As one of the primary power electronic converter technologies, traditional hard-switching inverter technology is mature and widely used. But when the switching frequency is very high, there will be lots of disadvantages to reduce inverter efficiency, just like high switching loss, big audio noise and poor system dynamic characteristics. The problems above are easily solved by soft-switching technology. In this context,a type of novel passive soft-switching three-phase inverter structure of topology has been proposed.Fistly, the development and the research significance of the soft-switching inverter are introduced in this thesis. Depending on whether the active switch exists or not, soft switching inverters can be separated into passive soft switching inverters and active soft switching inverters. Active soft switching inverter technoligy can reduce switching loss, but the way of control is complex. Passive soft switching inverter technology not only reduces switching loss and noise, but also have good characters of simple circuit, low cost, and high reliability. So it has been widely researched in recent years.Secondly, a new type of passive soft-switching three-phase inverter is proposed in this paper which has several advantages:(1) There is no need to change the original hard switching inverter control method, so it is very simple to control.(2) None active switching devices have been added into the hard switching circuit topology except some passive auxiliary devices such as capacitors, diodes and inductances.(3) The switching loss is reduced since the new inverter realizes soft-switching.(4) It can make a compensation about current during the dead-time by the action of energy storage device in the structure of topology, which could reduce the influence of current aberrance during the dead-time.Thirdly, this thesis analyzes the soft-switching operation mechanism of the proposed topology in detail based on the equivalent circuit figures of different working modes.Mathematical analyses of the dynamic process are also made. Control strategy is established to realize the inverter’s soft switching operation. After calculateing the loop parameters, some simulation are made under the Matlab/Simulink tituation. By comparing with the silumation result of geneal hard-switching inverter and analyzing the abberance ratio and stroboscope, the validity of topology structure and control strategy are verified. It realizes the soft-switching action of all the power switcher in the loop.Finally, a summary is made about the achivements and unsolved problems in this thesis. Some outlook of our researching work is made as well.