Impact of Low Switching-to-Fundamental Frequency Ratio on Predictive Current Control of PMSM: A simulation study
Predictive current control algorithms for permanent magnet synchronous (PMSM) drives rely on an assumption that within short intervals motor currents can be approximated with linear functions. This approximation may result either from discretizing the motor model or from simplifications applied to the continuous-time model. As the linear current approximation has been recognized as inaccurate in case when the drive operates with low inverter’s switching-to-fundamental frequency, it is expected that this inaccuracy affects precision of predictive control. This paper investigates the current prediction errors, related to the linear approximation, for an exemplary PMSM drive. Two methods are considered – a model based current prediction and a model-free algorithm. The analysis, carried out by simulation, reveals substantial errors that disqualify both considered prediction methods from applying them to drives operating with low switching-to-fundamental frequency ratio.
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