Research On The Techniques Of The Three-phase Unbalanced Inhibition For High Power Inverter

With the development of science and technology, the demand for high quality power supplyin modern electrical equipment is becoming more and more general. UPS (UninterruptiblePower Supply, UPS) has been widely used as it can provide clean, stable and reliable powerfor load in the utility fault or normal circumstances. In recent years, the developments ofadvanced technologies as power electronic technology, microprocessor control, automaticcontrol make UPS develop towards intelligent, networking, digital, green, high frequency andparallel redundancy. The quality of output voltage waveform is one of the key factor of UPS,which will be mainly affected by output voltage imbalance caused by the three-phaseunbalanced load. So it's very important for the inhibition of three-phase imbalance. Throughtheoretical analysis, experimental verification, digital control of UPS and solutions ofthree-phase imbalance are studied in this dissertation.Research of this dissertation is based on the cooperative project "Digitized ControlSystem for High Power UPS Based on DSP", which is created by South China University ofTechnology, school of Electronic Information Engineering and Guangdong ChuangDianElectric power co., Ltd. This dissertation researches deeply on SVPWM control technique andthree-phase unbalanced inhabitation technique of invertor.In this dissertation, SVPWM technique of invertor and DSP-based implementation of itscontrol algorithm on the basis of discussion of the fundamental principle are introduced. Forthe project this paper involved in, a corresponding SVPWM control strategy has beenproposed. It also analyzes the mechanism of output voltage imbalance under the condition ofthree-phase unbalanced load and deduces the negative sequence output voltage and zerosequence out voltage as the reasons for the output voltage imbalance. Two groups of PIcontroller in the d-q coordinates have been designed to solve the problem of output voltageimbalance. Finally, related experiments are carried out in the three-phase UPS 40kVAprototype, in which TMS320F2812 DSP chip is utilized as a main control chip, to verify thefeasibility and effectiveness of relative algorithm.