Hysteresis-based DIFC in SRM: Eliminating switching harmonics while improving inverter efficiency

Recently, it has been proposed to overcome the well-known acoustic problem of switched reluctance machines (SRM) by Direct Instantaneous Force Control (DIFC). By now, DIFC has employed a PWM-based dead-beat controller which causes strong modulation-related harmonics in the spectrum and does not adapt to the non-constant dynamics of the SRM. This paper aims to overcome both problems by hysteresis-based DIFC. A control scheme was developed and compared to the PWM-based approach by simulation. The presented spectrograms show that hysteresis-based DIFC makes modulation-related harmonics effectively vanish from the acoustic spectrum. Moreover, it requires lower switching frequency at equal acoustic performance such that the inverter efficiency increases. The paper shows that hysteresis-based DIFC improves acoustics as well as efficiency only coming along with more stringent demands to sensor technology - for what a solution is presented in this paper.