Construction Of Low-Power Test Platform Based On Scott Transformer For Oblique Co-Phase Power Supply

Since the 1950s,the development of electrified railway in China has undergone earth-shaking changes.However,due to the structure of traction power supply system and the particularity of load locomotive,the existing problems of traction power supply system mainly focus on the following two aspects:firstly,the unbalance of traction load,The negative sequence current and high-order harmonic content of the power system side will be increased,and the power factor will be reduced.Secondly,the traction power supply system adopts the power supply mode of phase sequence rotation at present.There will be excessive phase problems in the operation of trains between different power supply arms,which will lead to serious transient processes such as transient overvoltage and speed drop.The rapid development of electrified railway,especially high-speed railway,has been seriously restricted.In order to solve the problem caused by excessive phase,domestic and foreign scholars have put forward the method of in-phase power supply for traction power supply system,that is,all the power supply arms use the same phase sequence,which cancels and reduces the use of phase-separating insulators.In order to achieve this purpose,a power quality control device should be added to the traction power supply station to compensate for the influence of the in-phase power supply on the power supply system.Therefore,the research of co-phase power supply is of great significance for the development of high-speed railway.According to the research status of co-phase power supply both at home and abroad,this dissertation proposes a new type of power supply based on the assumption of co-phase power supply,that is to say,the oblique edge of Scott transformer is used for power supply,the so-called beveled edge,That is,the two auxiliary side windings of the transformer are connected in series to supply power to the load together.This kind of power supply is still a kind of unbalanced power supply mode.Therefore,the power flow controller based on the isolated AC-DC-AC power electronic converter is used to adjust the harmonic,reactive and negative sequence components generated by unbalanced power supply.The similarities and differences between this form and the traditional form of power supply are also analyzed.In this dissertation,the principle of PWM converter is introduced,then the extraction method of active and reactive power components of traction load is analyzed,and the corresponding traction load balance control strategy and modulation algorithm are put forward.The circuit model is built by MATLAB simulation software,and the low power system under laboratory conditions is simulated.The results verify the feasibility and correctness of the new structural balance strategy and control scheme.Based on the dSPACE real-time simulation platform integrated with H bridge and I/O port,through the selection and calculation of the relevant equipment parameters,the power grid simulator is used as the power supply to supply the Scott transformer of 220/275,and the oblique resistance inductance load is used to be the electric locomotive.The low power test platform is built to verify the effectiveness and reliability of the control structure by debugging it and the related waveform data collected by oscilloscope.It provides valuable experience for the development and development of high-power devices.