Resonant harmonic elimination PWM based high-risk harmonic resonance suppression in autotransformer fed electrified railway

The resonant harmonic elimination PWM (RHEPWM) method is brought to mitigate resonant harmonics in the harmonic source of an autotransformer (AT) fed electrified railway in order to suppress high-risk resonances (HRRs). Firstly, the coupling model consisting of a traction power supply network (TPSN) and a traction drive unit (TDU) of a high-speed train is established, and the HRR mechanism which indicates that the composite pulse voltage of the multiple four-quadrant converters in the TDU is the harmonic source is analysed based on it. Then the RHEPWM technology applied into the multiple converters is described thoroughly, and the target functions and initial commutating angles are decided based on the conventional carrier-shifting based sinusoidal pulse-width modulation (CSBSPWM). Subsequently, the optimal commutating angles are obtained by the rolling Levenberg-Marquardt (LM) method. Finally, the combined simulation model consisting of an AT fed TPSN and a TDU is implemented in a RT-Lab simulator, and the performance comparison between CSBSPWM and RHEPWM is carried out through the time-domain simulation. The results verify that RHEPWM not only has the capacity to suppress HRR, but also improves the total power factor and mitigates the distortion in the load current.