Reduction of Return Current Noise by Energy-Compensating Active Control

A newly proposed Energy-Compensating Active Control is implemented to reduce the return current noise which is caused by inverter-driven electric car systems. The Energy-Compensating Active Control detects the energy charged at the filter capacitor, reduces the energy and current of the noise frequency component by simple feedback loop incorporated with the conventional motor torque controller. No additional sensors or circuit arrangements are necessary, therefore the return current can be attenuated effectively without any further cost. The return current with an inverter system is measured using a current probe and a FFT analyzer, and it is shown that the 25Hz noise current is reduced by up to 10dB with the control. The results explain that the low frequency return current noise can be attenuated with the simple control scheme, which would expectedly reduce the size of filter reactors and capacitors to meet with the current limit level of signaling system's track relays.