Control of stator torsional vibration in PM brushless AC drives due to non-sinusoidal back-EMF and cogging torque by improved direct torque control

Abstract

This paper presents a comparative study of the stator frame torsional vibration induced in indirect-and direct-torque controlled permanent magnet brushless AC drives with nonsinusoidal back-EMF waveforms. An improved direct torque controller, which accounts for the influences of non-ideal back-EMF and cogging torque, is proposed. Its effectiveness in minimizing low order stator frame torsional vibration is validated and confirmed experimentally.Index Terms-brushless AC machine, direct torque control, permanent magnet, torsional vibration.

Reduction of Torque and Flux Ripples in Space Vector Modulation-Based Direct Torque Control of Asymmetric Permanent Magnet Synchronous Machine

“…Then, the stator flux-linkage magnitude and position can be obtained by utilizing either current (2) [12], [14], or voltage-model (3) [2], [13] based estimator as ˆ.…”

“…The output reference voltage vectors (RVVs) are generated using either one PI-regulator (cascaded) DTC-SVM [8], [9] or two PI-regulators (parallel) DTC-SVM [10]- [14]. The PI-regulators in torque and flux loops can be further eliminated if model predictive/dead-beat control strategies are used [15], [16].…”

“…Parallel DTC-SVM strategy, which employs two PIregulators for flux and torque control achieves a satisfactory performance when the machine is symmetric [10]- [14]. However, it is common that the electric machines are exposed to various types of asymmetries such as stator flux linkage distortion [1], non-sinusoidal back-EMF [14], [17], asymmetric phase impedance [18], errors in current measurements, and inverter nonlinearity [19], [20].…”

“…However, it is common that the electric machines are exposed to various types of asymmetries such as stator flux linkage distortion [1], non-sinusoidal back-EMF [14], [17], asymmetric phase impedance [18], errors in current measurements, and inverter nonlinearity [19], [20]. Such abnormal conditions lead to the rise of negative sequence components and parasitic harmonics at low frequency in the torque, speed, and flux linkage, i.e., 2 nd , 4 th , 6 th , and 12 th [14], [20]. These harmonics behave as alternative components (ac) overlapped with the original direct (dc) quantities.…”

“…The classic PI-regulator cannot control the ac components due to its bandwidth limitation [20]- [22]. Therefore, different control techniques have been presented to mitigate these harmonics [14], [19]- [26]. In [14], the authors compensate the influence of non-sinusoidal back EMF and cogging torque by improving the torque estimator, which requires the information about cogging torque, and only…”