Synchronous Continuous SVPWM Strategy for High-speed Maglev Three-level Active Neutral Point Clamped Traction Inverter

The design speed range of high-speed maglev is 0–600km/h. When the output frequency of the traction inverter is high, synchronous modulation strategies are required to ensure phase voltage symmetry and reduce harmonics. For the three-level active neutral point (3L-ANPC) inverter adopted in the high-speed maglev power supply system, a total of eight synchronous continuous SVPWM (SCSVM) strategies are proposed under the carrier ratio $(C_{\mathrm{r}})$ is an odd or even integer multiple of three, which can satisfy synchronization, three-phase symmetry (TPS), and half-wave symmetry (HWS). With the line voltage weighted total harmonic distortion (WTHD) as the standard, the switching sequence with the best harmonic performance is obtained under the same phase voltage halfcycle pulse number P. Moreover, two methods for realizing single-pulse SVPWM (SPSVM) are proposed, which have the characteristics of TPS, HWS, and quarter-wave symmetry (QWS). The SPSVM can also work in the overmodulation region. According to the optimal sequence of WTHD, a smooth switching method is proposed, which can avoid the two-level jump (TLJ) of the phase voltage. The proposed strategies are verified by simulation and hardware-in-the-loop experiments.