Cascaded H-bridge harmonic generator used for impedance-frequency assessment of traction power supply system

Resonance accidents of the traction power supply system which are caused by high frequency harmonic current are detrimental to the safe and reliable operation of the electric railway. It is important to study the resonant frequency characteristics of the traction power supply system. Based on the harmonic injection method, a novel harmonic impedance measuring scheme of the traction power supply system was proposed. The method adopts the cascaded H-bridge and the hierarchical control strategy. Different harmonic currents can be injected into the traction power supply system through a boosting transformer. Then the harmonic impedance and the resonant frequency can be calculated with the measured data. The simple system, does not need detailed structure and parameters of the traction network, is valuable and reliable for practical applications.