The DC Link Of Power Electronic Transformer

Traditional transformer has a wide range of applications in power systembecause of its outstanding stability and high efficiency, but its weight and volume isvery large and its lack in dealing with the power quality problems in recent years isalso gradually apparent; At the same time, the power electronic technologyrepresented by Flexible AC Transmission Systems has a successful application inpower system, so whether power electronic technology can be used in transformerfield to improve the problems of traditional transformer or not becomes a researchfocus and the concept of power electronic transformer(PET) comes into being.The DC link with high frequency is the key part of power electronictransformer and it has a great effect on efficiency and size of the device.This papertakes the DC link as the main study object and analyse the effect and problems on it,then adopts soft switch technology in order to reduce the loss of PET and promotehigh-frequency be applied in PET. Through the comparision of three kinds of DC-DC converter, this paper determines to adopt the ZVZCS full bridge three-levelconverter as the DC-link, then gives the topology.As a new type of power electronic devices, PET should also have the ability ofimproving power quality besides the base function of voltage regulation, isolationand energy transmission. This paper sets the corresponding control strategy towardsthe three links of PET and proves that it has the functions of achieving power factorcorrection, resisting voltage fluctuation, suppressing harmonic diffusion and dealingsudden load change and voltage flicker.In this paper a lab prototype whose control chip is DSP is built based on thetheory analysis and simulation experiment. The selection of parameter and thedesign process of software and hardware are introduced in this paper. The functionof soft switch of the DC link and the abilities of voltage regulation, isolation andenergy transmission of the PET are realized through the hardware experiment andits results prove that the DC-DC converter researched in this paper can be used inPET.