Researches On Single-phase UPS And Its Digital Control

With the rapid development of modern communication system and the massapplication of advanced equipments, UPS (uninterruptible power supply), as the powersupply of these equipments, has been widely used. Meanwhile, the demands for thereliability, the flexibility and capacity of UPS power supply system are increasing andhigher.By controlling the two switches of the interleave PFC (Power Factor Correction,IPFC), the Boost converter works in staggered180degrees. Compared to the single BoostPFC circuit, at the same switching frequency, the current ripple of the inductance can getthe multiplication frequency effect, and higher input power factor and the current THD(total harmonic distortion). Thus, the output power of the single-phase circuit is increased,which meets the new requirement of UPS.With the advantages of simple circuit structure and mature theory of the full bridgeinverter (FBI) circuit，and the feature of the output voltage of the interleave PFC Boostconverter，which can be connected to the full bridge inverter directly, and no need to otherintermediate processes. So the combination of IPFC and FBI will be a good choice, whichcan be used as the rectifier and inverter topology of UPS. Firstly, the feature of the IPFC isintroduces, in this article, and the operating characteristics is also analyzed, the controlscheme is given as well. And then the characteristics of the FBI is introduced in detail, thecontrol method is put forward to improve the ability of the system with nonlinear load.Finally, the validity of the theoretical analysis and the feasibility of the control strategy areverified by simulation, which proved the practicability of the combination of the twocircuits used in the single phase UPS. Along with the development of microprocessors anddigital control technology, more and more high performance digital processors such asDSP(Digital Signal Processor) is introduced into the UPS control system, UPS changedfrom analog to digital control.A new single-phase UPS digital prototype is built in this paper, with IPFC being thefront-end and FBI being the rear-end. The TMS320F2810DSP control chip of TI has been used for digital control. The theoretical analysis is validated and the effectiveness of thecontrol method is proved by the experiments, and high PFC is achieved by the results withthe proposed topology. Also, the high practical value is proved in the experimental resultsby using the proposed topology of the digital single phase UPS.