Characteristics analysis and reduction of the high order harmonics of DC-link voltage for railway traction converters

Aiming to suppress DC-link voltage harmonics of dual PWM rectifiers with DC-link parallel connection in electrical traction AC drive system, the operating principle of single-phase PWM rectifier is firstly introduced in this paper. Then the characteristics of DC-link voltage harmonics in the steady-state are derived, and the effect between carrier phase-shifting technology and DC link voltage harmonics of the dual PWM rectifiers is analyzed in detail. Theoretical analysis shows that the high order harmonics of DC-link voltage are mainly distributed around the twice switching frequency, and the carrier phase-shifting technology can suppress the DC-link voltage harmonic coefficient through reducing these high order harmonics. Finally, the performances of carrier phase-shifting and non-carrier phase-shifting technology are verified in computer simulation and hardware-in-the-loop(HIL) experiment system tests, respectively. And both of the simulation and experimental results verify the validity and effectiveness of theoretical analysis.