Critical Issues of Alignment Procedures for a Novel Single-Stage Current Source Inverter With Discharge Path

The intrinsic boost capability of the current source inverter (CSI) increase the power density of the machine and this is of interest in aerospace and electric vehicles (EVs) applications.With the classical power converter, the machine can work only in a limited range above a base speed. In this scenario the alignment of the rotor is forbidden due to the uncontrolled increase of the DC current. A recently proposed single-stage CSI with discharge path allows to achieve the whole speed range extending the operating region of the converter down to zero speed. In this way it is possible to align the rotor during the power-up phase in a controlled way avoiding unwanted behaviors of the DC current. Unlike voltage source inverter (VSI) architectures that have a constant DC voltage, with single-stage CSI the DC current depends on the working condition and is not constant. For this reason, it is not possible to use the common alignment on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</i>-axis of the stationary reference frame because the active vectors exhibit different mean values due to the variations of the DC current. An alignment procedure for electric drives that employ an incremental encoder for position sensing is designed for this power converter, using a rotor position alignment on one of the active vectors with a predefined startup procedure without the use of any signal injection. Simulations and experimental results show the effectiveness of the proposed solution.