Research On Novel AC-Link Charging Technology And Its Control System Design

Great convenience was brought to electric power conversion and utilization by wide use of power electronic equipment, but also lots of harmonic pollution was brought to the power system and other electronic equipments. Therefore, improving the power factor and reducing the current harmonic has become a research focus and major issues of electronic technology.The traditional electronic devices have some inherent defects which brought a large number of harmonic current and reactive powers to the grid. If the pollution of harmonics and reactive power was not properly governed, it will cause a power system failure or lead to the breakdown of other electronic devices. Currently, the primary approaches to solve the problem of harmonic power in electronic devices lie in that:power filter and power factor correction technology. Both of the two solutions have increased the system's cost, size and weight.AC-link technology is a new type of power electronic conversion technology which has been first proposed by foreign scholars in the late 20th century. This technology eliminates the need for traditional power electronic devices in the rectifying part, directly transform the three-phrase AC into high frequency pulse, then transform the high frequency pulse into needed power form. Thus low power factor and high harmonic content problem of traditional power electronic devices was solved. AC-Link is a high frequency resonant transform technology, thus the loss and di/dt is small, then the efficiency and power density was enhanced and perfect EMC performance was obtained. Meanwhile, AC-Link is flexible transform technology that can transform power in all power form.Variety of AC-Link configuration was widely investigated in this paper. Then typical AC-Link converter was analyzed and simulated and the basic characteristic and control method was given out. A novel AC-Link charging technology was researched and simulated in the paper, the result show that this novel configuration is suitable for capacity charging applications. It combines high power factor and low harmonic character of AC-Link and natural constant character of DC-Link series resonant configuration. Meanwhile, this novel configuration can operate in constant current or constant power mode.Finally, A FPGA based controller of AC-Link technology was fulfilled. The result of simulation and experiment show that under the control fulfilled controller the experimental equipment can operate in a good state and high power factor and low harmonic content was obtained.