The Research On Three-phase Delta Transform UPS

Traditional double transform UPS(that is AC/DC and DC/AC transform) is not efficient and unable to utilize power sufficiently, moreover it produces heat greatly, so the probability of equipment malfunction is increased; and the online interactive UPS has some disadvantages which the output voltage accuracy is not high and there is no function of adjusting. A kind technology which arises in the domain of electricity power compensation is studied in the paper, which is Delta transform technology. This UPS have the good virtues of the traditional dual conversion UPS and their shortcomings are overcome.In this dissertation, the analysis of the theory of Delta conversion UPS is firstly made. It shows that the combined power quality regulation of UPS can be achieved by controlling the Delta converter as a sinusoidal current source and the main converter as a sinusoidal voltage source.The separate operation of the Delta converter and the input current control are studied. In order to suppress the influence of non-ideal input voltage, two effective control methods are introduced. One is three phase ABC individual control and the other is dq+0 axis control. The voltage unbalance between the two group capacitors is analyzed and a simple and valid method is provided. Simulation results verify the validity of the control methods.The separate operation of the main converter and the output voltage control are studied. For unbalanced and nonlinear load bound to lead to the imbalance and harmonic output voltage of the main converter ,the corresponding two control strategies are introduced, which are three-phase individual control combined repetitive control and the introduction of negative sequence control and harmonic control based on the dq+0 axis control. Simulation results verify the effectiveness of these control methods。Based on the coordination control strategy of the Delta converter and the main converter, the three-phase four-wire Delta transform UPS system is simulated under various working conditions. The results shows that the UPS system can well adjust the unified power quality of the input line current and the output load voltage.