Research On Three-phase To Single-phase Balance Compensation Power Supply Mode Based On Vv Transformer

With the continuous development of the national economy,a large number of single-phase high-power loads(such as resistance furnaces,electric locomotives,partial ore heating furnaces,alternating current welders,oil field heating equipment,etc.)have appeared in the power grid system,making the three-phase power system unbalanced.And the problem is becoming more and more prominent,which seriously endangers the safe and reliable operation of the power grid system.In order to comprehensively solve the power quality problems caused by the single-phase load access three-phase system,and simply and reliably realize the three-phase/single-phase balance conversion,a three-phase to single phase balance compensation power supply mode based on Vv transformer is proposed in this paper.Mainly completed the following aspects of the work:Firstly,the three-phase to single-phase balanced power supply method based on Vv transformer and LC method(phase-shift)was studied,which was abbreviated as Vv-LC scheme.The structure,working principle and advantages of Vv transformer are analyzed.Combining with the characteristics of Vv transformer,the conditions that it needs to meet for balanced power supply are studied.The circuit topology of different properties of the loads is discussed.Considering the symmetry of three-phase side and high power factor conditions,a set of formula for calculating the parameters of the matching element is derived,and the simulation of the proposed topology is carried out.The simulation results verify the correctness and feasibility of the Vv-LC scheme.Then the three-phase to single phase balanced power supply mode based on Vv transformer and static var generator(SVG)is studied,abbreviated as Vv-SVG scheme.The structure,working principle,working characteristics and advantages of SVG are analyzed.According to the properties of the load,two different Vv-SVG system structures are created,the working principle of the corresponding system is studied,a scheme to realize the Vv-SVG system is designed,and the hybrid compensation,the cascade of H bridge and parallel structure of the three-phase/single-phase balance transformation are constructed.Then the control strategy of Vv-SVG system was studied.A comprehensive compensation current detection and control method suitable for Vv-SVG system is proposed.Finally,in the MATLAB/Simulink environment,the Vv-SVG system simulation model is established,and the actual cases are simulated.The actual technical parameters are selected to simulate the changes of the system before and after the input of the compensation device.And under the designed detection and control scheme,the system can achieve the goal of symmetrical three-phase current,low negative sequence content and unit power factor on the three-phase input side.Simulation results verify the correctness and feasibility of the Vv-SVG scheme.