An Integrated Fast Resettable Integrator Circuit based on Switched Capacitors for Sensorless Control of PMSMs

Abstract:
Permanent Magnet Synchronous Motors (PMSMs) are a widely applied drive solution in many application fields due to their compact and robust construction as well has high power density. For an efficient operation, the rotor angle is required, a quantity which is typically measured by position sensors that increase system size and cost. A possible solution to this is sensorless control. In particular, the Direct Flux Control (DFC) technique estimates the electrical rotor position by evaluating the zero-sequence voltage of a PMSM under modification of the PWM voltage. In practical implementation of this technique, it is desired to increase the delay present in the PWM in order to increase the signal-to-noise ratio of the estimation. Consequently, the maximum driving voltage cannot be applied. With the help of a Fast Resettable Integrator circuit (FRIC), the delay can be reduced while increasing the signal-to-noise ratio. Beside these advantages, the FRIC allows a more accurate estimation for usage in parameter identification problems. Since the implementation of the FRIC can be cumbersome, this work presents a realization of the FRIC based on the Switched Capacitor (SC) technology, that allows for tighter tolerances as well as size and cost reduction, which is preferable for the usage in small electric drives. The work introduces the basics of FRIC, its implementation in SC technology and experimentally compares the performance with the standard DFC- as well as the FRIC-based rotor position estimation.