Research On PFC Of Full-digital On-line UPS

With the fast development of information technology, digital CVCF-PWM power supply become possible. The performance of the on-line UPS is the best among all kinds of UPS, and it is widely used in many fields. But because the on-line UPS needs the DC voltage from the rectifier, in order to reduce the harmonic pollution caused by the non-control rectifier, this dissertation focuses on the study of a designing method of PWM rectifier with power factor correction (PFC) that applied in the on-line UPS.This kind of rectifier can reduce the pollution to the supply by the on-line UPS, and make the source become 'green'. This dissertation introduces analyzing and designing method of a digital PWM rectifier, and the core control chip is TMS320F240.At first, the current and future development of UPS and the technology of the PWM rectifier are summarized. Then, the state-space model of the system are analyzed and established based the characteristics of the rectifier used in this system. The work mode, the work condition and the problem in the system also discussed. The solution for the problem is presented. All control methods are confirmed and analyzed using the Matlab software.After the characteristic of the TMS320F240 chip is taken into account, in this dissertation the UPS system based DSP is presented. By insulating the source and the ground between the power circuit and the control circuit, the stability of the system is improved, and the disturbance of the system is reduced. The detection circuits of voltage, current and correlative protection circuit are discussed in detail.After comparison of all control methods for this system is discussed, the predictive control method is used and the improvement of the conventional control method is presented. The validity and feasibility of the method is confirmed by the experiment.The software design of the system is described. The digital methods to generate the sine wave, the interruption and some important flowcharts are all presented in detail.At the end of this dissertation, the experiment results of the system are provided, and these results show that the proposed control scheme can stabilize the output DC voltage and unit power factor.