Arbitrary injection based sensorless control with a defined high frequency current ripple and reduced current and sound level harmonics

Most Anisotropy based sensorless control schemes are using an additional voltage injection in order to create a measurable current ripple. This injection causes some unwanted side effects such as additional noise and torque oscillations, introduced by the harmonics of the current. This paper proposes an operating point dependent injection in combination with an arbitrary injection scheme in order to reduce these disturbances. It avoids, that more voltage is injected than needed during saturation, this results in reduced current and acoustic noise harmonics. The method includes an approach, how to define the injection amplitude in order to produce a measurable minimum high frequency current ripple. The method was developed with the aim to be easily implementable, without additional measurements and with less computational effort. The operating point dependent injection is verified by simulation and measurement results. For the illustration of the method a triangular shaped injection is used exemplary. The process is carried out for a reluctance synchronous machine.