OWIM Drive Operated With Synchronized PWM With Odd-Non-Triplen and All-Triplen Pulse Numbers for Railway Traction Application

Two-level voltage-source inverter (VSI)-driven squirrel-cage induction machines (SCIMs) are the most popular choice for electric propulsion in the railways. VSIs in such systems are operated with low switching frequency (
$f_{\text{sw}}$

$\leq$
500 Hz for a fundamental frequency
$f_{m}$
of 65 Hz) to curb switching energy losses. Pulse number (
$P$
, ratio between
$f_{\text{sw}}$
and
$f_{m}$
) is maintained at odd-triplen integers (i.e., 3, 9, 15, 21, etc.) for carrier-based synchronous pulsewidth modulation (PWM) techniques. Such motor drives suffer from high
${dv}/{dt}$
stress, poor line current quality, and large current transients. This article proposes an open-end winding induction machine (OWIM) drive for railway propulsion. The proposed system includes minimal modification in the existing structure. However, it reduces the
${dv}/{dt}$
stress and improves line current quality significantly. Furthermore, a multiple-carrier-based synchronized sine-triangle PWM technique is proposed to incorporate odd-non-triplen (5, 7, 11, 13, etc.) and even-triplen (6, 12, 18, etc.) pulse numbers apart from standard-triplen pulse numbers. Thus, variation in
$f_{\text{sw}}$
is restricted within a narrowband over the complete range of speed. The performance of the proposed OWIM drive is compared with that of the SCIM drive in simulation on an open-loop constant
$V/f$
-controlled 850-kW traction system. The same is also validated experimentally on a 3.7-kW laboratory prototype.