Parallel Harmonic Resonance Probability Identification of Traction Power Supply System Based on Measured Data
Pulse width modulated four-quadrant converter is widely used in the high-speed railway electric locomotives in China at present.While its performance is improved,it also brings higher harmonics with wider frequency bands,which is more likely to stimulate harmonic resonance in the traction power supply system.The overvoltage or overcurrent caused by the harmonic resonance may in turn lead to equipment explosion,protection mis-operation and other safety accidents in severe cases.Therefore,it is of great significance to accurately identify the potential resonant frequency of the system.The commonly used methods,such as the frequency scanning analysis and the resonant mode analysis,depend on the accuracy of the system topology and the models.However,the accuracy of those traditional identification methods based on measured data is greatly affected by system parameter fluctuations and background harmonics.Therefore,this paper proposes a parallel resonance probability identification method for a traction power supply system based on measured data.The cosine similarity of the voltage and current waveforms is used as the resonance prediction condition to reduce invalid calculations.The probability analysis of multi-level resonance characteristics like the fundamental/harmonic power factor and the system harmonic impedance amplitude overcomes the influence of the system parameter fluctuation and background harmonics.Simulation research,measured data analysis and comparison with the existing research methods show that the proposed method is applicable even when there are strong load fluctuation and large background harmonics,and that the recognition accuracy is higher,which verifies the effectiveness and reliability of the proposed method.