Study On Full Digitized On-Line UPS Based On Parallel Operation

With the development of science and technology and the improved requirement of the client, Uninterruptible Power Supply (UPS) system, as an important power electronics device, is widely used for supplying critical loads which can not afford utility power failure. In order to improve the performance and practicability of the UPS, this paper focuses on the digital parallel on-line UPS by the means of analysis, design and experiment, receiving some useful conclusions and experience. Firstly, some topologies of AC/DC conversion are studied. Because of the difference of the power stage and the technique requirement, the required topologies of the rectifiers are also different. In this paper, some different AC/DC topologies are analyzed and the corresponding control tactics are presented. For realizing the fully digitized control, the scheme of digitized control and the experiment results are presented according to the main topology and the work condition, which performs very well. Battery correlates the AC/DC conversion of UPS closely, and also is respond to no supplying failure, so the charge and monitor of the batteries is disserted in this paper. Then, the more attentions are pay to the research on the digitized control of DC/AC conversion of UPS. From the mathematic model of the single-phase half bridge inverter, the control tactic of PI dual-loop with the forward feed of output current is presented. Because of the control delay of the digital control, the design of the state observer is presented. For designing the parameters of the digitized control system, the method of pole configuration is presented, which satisfies the required dynamic and static performances. The experimental results demonstrate that the control scheme can resolve the problems well and the process of this scheme is easy. Otherwise, to improve the capacity and reliability of UPS, it is a good choice to applying parallel operation techniques. The characteristic of the parallel operation is analyzed, and then the realization of digital PLL (Phase Locked Loop) is discussed and the control tactic of circle current is presented in this paper. At last, according to the characteristics of CAN bus, the method, which achieves communicating the run parameters and monitoring the run states when the UPS system is running, is presented.