Integration of transient and fundamental wave excitation for zero speed sensorless control of AC machines

To realize a field oriented control of ac machines that is able to work at zero speed the most commonly used methods are either sensor based models or transient signal excitation methods. In this paper a new evaluation algorithm based on phase current derivation to extract the flux position information is presented. This method is working without additional transient excitation of the machine and requires only the fundamental wave excitation using standard PWM or a slightly modified PWM. Only the current response in the active states of the PWM is exploited, to avoid parasitic influences during the zero switching state. Measurement results are presented to validate the applicability of the presented approach.