Research On The Technique Of Phase-Lock And Parallel For Wireless Parallel System Of Single-Phase UPS

With the development of informationization, users’ demands for the quality of power system become higher and higher, UPS (Uninterruptible Power Supply) have been applied more and more as the power supplies of key equipments in important occasions. And with the increase of the electric equipment, users’demands for the reliability and capacity of UPS power system also improve gradually. Base on the background, the control technology of modular parallel UPS system is becoming an increasingly important area of research. Based on the summary of the existing UPS parallel control theory and applications, the realization method for single-phase UPS is analyzed and discussed, which is focusing on the control method.The paper first briefly introduces the research situation of UPS. Based on the analysis of the advantages and disadvantages of the existing UPS control method, reasonable system structure and related control method are being chosen, including the respective control method of the two converter, as well as the related control of the whole UPS system.While UPS switches to bypass working mode, a very large circulation will be produced. In view of the phenomenon, and based on the detailed analysis of the exiting digital phase locked technique, a phase lock method of the UPS system is proposed in the paper. First the phase lock method for the single system is presented. Then based on the analysis of the contradiction between the wireless parallel control and the phase lock, several improved coordination methods are proposed gradually. And after the analysis of the several coordination methods, a kind of improved coordination control method is chosen to alleviate the contradiction. Then the experimental results show that the rationality of the design method.Then this paper gives the limitations of the classical wireless droop control method, while the parallel system interconnector impedance is resistive-inductive and different. In order to improve the phenomenon that parallel system has poor current sharing under different interconnector impedance, the paper improves wireless droop control from the aspect of line impedance voltage compensation. And then based on the analysis of the small signal modeling, this paper selects the appropriate droop parameters of the improved droop control method. Finally the new control strategy is validated by simulations and experiments.