Research On Harmonic Transformation Characteristics Of Train Roof Voltage Transformer

In the traction power supply system,abnormal voltage caused by harmonic resonance occur from time to time.Serious voltage quality problems may cause damage to the insulation of the train or ground equipment,increase losses,and even train shutdown.The roof voltage transformer is the only voltage-transformed equipment in the high-voltage electrical equipment on the train roof.It transforms the high voltage of the catenary into a low voltage on the secondary side to supply power to the secondary measurement equipment or relay protection device on the train.In the power frequency state,the voltage transformer can accurately transform the catenary voltage into a low voltage on the secondary side;under harmonic conditions,the harmonic transformation error of the voltage transformer will increase,and the accuracy of voltage measurement cannot be guaranteed.Therefore,it is necessary to study the harmonic transformation characteristics of the roof voltage transformer,grasp the transformation law of the voltage transformer under the harmonic,discuss the factors that affect the accuracy of the voltage transformer harmonic measurement,and improve the measurement of the voltage transformer under the harmonic The accuracy ensures that the secondary equipment of the train works reliably and stably,so that the train can operate safely and stably.This thesis studies the measurement problem of high-voltage voltage transformer on the train roof under harmonics.Through the combination of theoretical analysis and experimental measurement,the factors that affect the transformation error of voltage transformers under harmonics are studied.The transformation errors of voltage transformers of different manufacturers under harmonics are established.A harmonic model that can accurately reflect the voltage errors of voltage transformers under harmonics is established.The transformation errors of voltage transformers under harmonics are corrected and finally carried out test verification.The main research work is as follows:(1)From the perspective of the structure of the voltage transformer,introduce the similarities and differences between the roof voltage transformer and the traditional transformer,theoretically analyze the influence of harmonic voltage on various parameters of the voltage transformer,and conduct parameter calculation.(2)Conducted laboratory test and measurement on the harmonic transformation error of the voltage transformer.In order to study the influence of the voltage change of the contact network on the primary side of the voltage transformer on its transformation characteristics,pure harmonic test,fundamental wave and harmonic superposition test were carried out,respectively,by measuring the voltage transformer primary side and secondary side voltage,Through FFT analysis,the law of the influence of the primary voltage on the harmonic transformation characteristics of the voltage transformer is obtained.(3)Establish a model that can accurately reflect the harmonic transformation characteristics of the voltage transformer,and analyze the effects of various parameters of the model on the transformation characteristics of the voltage transformer.Derivation and analysis of the transfer function of the voltage transformer,through a series of experiments to obtain the various parameters of the voltage transformer model,build a voltage transformer harmonic model in MATLAB / Simulink,by changing the size of different parameters,each parameter to the voltage mutual inductance the effect of the harmonic transformation characteristics of the transformer.(4)To correct the measurement error of the voltage transformer under harmonics,use a quadratic polynomial to fit the actual transformation ratio,and use linear fitting to the phase difference to find the actual transformation ratio of the voltage transformer and the difference between the phase difference and the frequency law.Use the fitted voltage ratio and phase difference to correct the harmonic error of the voltage transformer.The test verifies that the correction method has certain accuracy,and provides a new idea for solving the harmonic measurement problem of the roof voltage transformer.