Transient operation of carrier signal injection based sensorless techniques

This paper analyzes the interactions between the fundamental excitation and the carrier signal used for estimation in carrier signal injection based sensorless AC drives. While these interactions can be minimized during steady-state operation through filtering, transients in the fundamental excitation are not so easily treated. The analysis presented covers both negative sequence carrier signal current and zero sequence carrier signal voltage based sensorless methods. Both of these methods are shown to suffer from similar effects due to their interactions with the fundamental excitation. Techniques for mitigating these effects are developed and analyzed for both methods.