Interaction between the current controller and the injection of alternating carriers in sensorless drives

The injection of an alternating voltage carrier, which is generated by the inverter, allows to detect the rotor position in PM synchronous motors by evaluation of the anisotropies. There are however some limitations on the carrier frequency. On one hand, it must be much lower than the inverterpsilas switching frequency. On the other hand it must be high enough in order to avoid being attenuated by the current controller. As the current controllers are usually designed to reach the highest possible bandwidth, in the proposals for carrier-based position detection methods their bandwidth are limited. In this paper, the interaction between the current controller and the injected carrier is studied. A method to keep the highest bandwidth for the current controller while maximizing the carrier path gain is proposed in order to optimize the position detection.