Silent injection for saliency based sensorless control by means of current oversampling

Abstract

Sensorless control approaches for low and zero speed determine the rotor position by injecting high frequency voltage signals. Current measurement noise and quantization necessitate a minimum amount of injection amplitude, which implies an acoustic noise emission that for many applications is unacceptable. This paper proposes to sample the current with the maximum A/D conversion frequency while processing the data with an FPGA. By means of a recursive least squares method and an algorithmic extension, high precision current slopes are calculated from low injection voltage. Experimental results show that the injection magnitude can be reduced by factor 7 to 10 compared to standard PWM centered current measurement.

Silent and parameter independent hybrid sensorless control for SPMSM based on current oversampling

“…7: Reference speed step from standstill to half rated speed and back indicates the speed controller bandwidth of about 16/s (2.5Hz), for which the q-current command is still smooth. However, in comparison to parametrized hybrid methods that have been implemented at the same test bench [13], [19] this dynamic performance is relatively weak, which advises the application to systems with increased inertia.…”

“…In continuation of [13] this paper proposes further ways of utilizing the oversampling data: In standard SPMSM 1 operation (no saliency and i d = 0) the passive state current slope reveals the EMF position independent of machine parameters and unaffected by the IGBT interlock time. The Arbitrary Injection scheme [14] is naturally free of machine parameters.…”

“…However, each current sample is subject to measurement noise and quantization, which impairs the performance of the sensorless methods and necessitates a clearly audible amount of HF injection around zero speed. The latter issue has been addressed in [13], where the actual sampling rate potential of commercial AD converters has been exploited to obtain the anisotropy position even under very weak injection. A least squares algorithm approximates high precission straight parameters from the current evolution during the passive switching states (zero voltage) of the PWM.…”

Analytical Design of Self-Sensing Control for PMSM Using Quasi-Direct Calculation

“…For this purpose, the stator voltage equation is brought into a form, that leads to a simple calculation of the residual (and its partial derivative, which is also needed for the optimization process). For this purpose, current oversampling according to [9] and [10] is used to measure the current slopes within a pulsewidth modulation (PWM) period. As excitation, a square-wave injection (SWI) [11] is used.…”

“…Compared to the state of the art, the simple description of the transfer function leads to advantages during commissioning. In the majority of the publications, the design of the parameters of the SSC and the speed control is not described [2], [3], [5], [6], [7], [8], [9], [10], [11]. While the publication [13] gives rules for the parametrization of the position estimation, speed control is not addressed.…”