High-voltage Large-capacity H-bridge Series Inverter

The energy source production and consumption are huge in China, but the situation of wasting energy source is a serious issue for a long time. According to the statistical data, in China only the power consumption of fans and pumps take the 40% of annual electric power production. It has been proved by theory and practice that variable speed motor drive can at least save electric power more than 20%, even to 70% in some situations. The background of this dissertation is based on a project of researching and developing a high voltage series H-bridge multilevel converter, which drives an induction motor of 6300V, 2240kW for driving a water flooding pump in Taigang. The research work on high voltage high power series H-bridge multilevel converter has been carried out by theory analysis, computer simulation and experiments.The series H-bridge multilevel converter's power circuit is composed of uncontrolled rectifier with filtering capacitor and single phase H-bridge voltage-type inverter. As a result of employing multilevel phase-shifted method with zig zag connection in transformer secondary, in the primary the current harmonics their orders are lower than 6M 1 are eliminated (M is the number of power cell each phase). In the inverter side because of using pulse shifting PWM control, the equivalent switch frequency of output is M times as high as one H-bridge, so the output voltage waveform of the inverter is near sine with less harmonics.The series H-bridge multilevel converter has the advantages of high output voltage, high power, lower harmonic content in line and motor sides and high input power factor. In addition, because of blocking design, it is easier to raise output voltage, trouble shooting and maintains. Moreover, the converter has no specialdemands on the motor, so it is good for revamping old systems.This dissertation overviews the current development situation of high voltage high power converter, and introduces the topology structure and working principle. In the paper it makes focal points of the zig-zag transformer' influences on the harmonics of line side and pulse shifting control influence on the harmonic of motor side. The theoretical computation and computer simulation waveforms are presented. Finally the engineering design parameters of the system and the experimental waveforms are given. From experimental results we can see that the real test results are consistent with the theoretical analysis. The equipment of series H-bridge converter has been test running now in Taigang.