Stable and Passive Traction

In this thesis we discuss and analyze aspects and methods for low-speed poeration, startup, and particularly rotational reversal for sensorless control of non-salient permanent-magnet synchronous motors (PMSMs), i.e., stabilization in the low-speed region. Furtermore, a speed and position estimation algorithm for speed-sensorless control of electrically excited synchronous machines (EESMs) with damper windings is developed. For EESM drives, an initial rotor position estimation algorithm is also developed. Regarding the PMSM drives, it is shown that the sensorless drive synchronizes from any initial rotor position, recovers from initial rotation in the wrong direction, and also reverses rotation without lockup or instability phenomena.The result regarding sensorless control and preformance in the low-speed region are simulated and experimentally verified, which indicates that the proposed estimator is effective. An additional subject in this thesis is control traction converters. One major problem is that trains with pulse-width-modulation (PWM) converters have active input impedance; thus the phase shift between the input current and voltage is greater than +90 degrees or less than -90 degrees for a certain ferquency region. This may result in poor damping and in worst case unstable operation. Here, it is shown that via sophisticated current control and improved feed-forward, one may stabilize the system with respect to passivity.