Pressure Multi-level Inverter Device

Recently, for the medium and high voltage inverter equipment, it is focused on the application of multi-level converter and that topology of multi-level inverter is a preferred candidate in the medium-voltage equipment. In this dissertation, the problem which is interrelated with the topology of three-level H-bridge cascade type multi-level inverter with clamped-diode is investigated in detail;1. First of all, conventional topology and modulation method are respectively generalized, consequently, topology of three-level H-bridge cascade type multi-level inverter with clamped-diode is specified, furthermore, both operating principle and mathematical model are presented.2. Modulation schemes those appropriate to the specified topology are analyzed in detail. Considering the character of ultra-multi output level, optimized harmonic step modulating technique is adopted, and furthermore, theory analysis and simulation investigation are implemented. Considering characters of the basic unit that is three-level H-bridge structure with clamped-diode and the cascaded units construct each phase, three carrier modulation schemes based on cascaded carriers and phased-shifted consideration are presented, and their respective implementations are correspondingly specified, furthermore the feasibility are verified by simulationresults, finally, comparison analysis among the schemes is implemented.3.A cost-effective strategy is proposed for signal isolation and communication using optical fiber to solve the problem of signal isolation and communication existing in the medium-and-high-voltage equipment. A number of optical fibers can be saved by coding the parallel PWM signals in serial and then decoding them into parallel. It also can solve the related problems in other high-power applications.4.From the angle of modularization and expandability, a experimental prototype of the medium-multilevel inverter is designed, in which a technology based on the patent of high frequency AC bus is adopted to design all 57 isolated auxiliary power supplies for the equipment. Finally the experimental results validate the strategy.