A novel PLL scheme for a sensorless PMSM drive overcoming common speed reversal problems
International Symposium on Power Electronics Power Electronics, Electrical Drives, Automation and Motion
The work developed in this paper presents the building steps of an improved PLL algorithm, called "Extended PLL" , that is specifically designed to be suitable to overcome many co mmon issues coming fro m speed-reversal operations that are affecting the standard phase-detection algorithms normally used in most back-EMF-based sensorless strategies. A complete analysis of the features offered by the proposed novel PLL scheme will be presented from different points of view even though, first of
... , the build ing procedure of the imp roved structure of the algorith m will be introduced. The new scheme is mainly based on a proper definit ion of a specific nonlinear error function that gives to the algorith m several enhanced stability properties. Cause of its non-conventional constructive procedure, a formal proof of the new features has to be given through a specific stability analysis. In addition to this, another key point of this work will consist in a proper co mparison between the new algorith m and some standard solutions fro m the point of v iew of the performances with respect to the robustness against implementative imperfections, in order to enrich the present study. Such imperfections are introduced to take into account most of the practical knots involved in the implementation of the overall sensorless strategy on a real drive; in the present case study they can be grouped mainly in two categories: DC offsets and additive harmonics. The analysis were done using Simu lin k and hardware-based Real-Time simu lations, the results obtained under ideal and non ideal operating conditions and during speed-reversals will be fu lly detailed and discussed in the conclusions.