Injektion raumzeigerzerlegter Stromharmonischer zur Minderung tonaler Geräuschanteile in asymmetrisch sechsphasigen Permanentmagnetsynchronmaschinen

• Vector space decomposed current injection to mitigate tonal noise components in asymmetrical six phase permanent magnet machines

Hollstegge, Philipp; de Doncker, Rik W. (Thesis advisor); Doppelbauer, Martin (Thesis advisor)

Aachen : RWTH Aachen University (2021)
Book, Dissertation / PhD Thesis

In: Aachener Beiträge des ISEA 157
Page(s)/Article-Nr.: 1 Online-Ressource : Illustrationen, Diagramme

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021

Abstract

Although the noise emission of electric drive trains is lower in comparison to combustion engine drives, the noise spectrum is dominated by few tonal components. These components have a negative impact on the sound impression and thus on the comfort in the driver’s compartment. It is known that current harmonics have an influence on the Noise Vibration Harshness (NVH) behavior. However, their control is limited in terms of speed range due to lack of voltage reserve. Moreover, the natural frequency of the noise-critical breathing mode is often excited at the beginning of the field weakening region, where in addition to the low voltage reserve, the rotor skew is less effective. This thesis contributes to the understanding of how at the beginning of the field weakening region, a six-phase permanent magnet synchronous machine with 30° phase shift, the so-called asymmetrical six-phase machine, is regulated with NVH-optimized control. The asymmetrical six-phase machine offers advantages in the control of current harmonics. Due to their topology, current harmonics are opposed with low a impedance resulting in a wide usable amplitude range at the beginning of the field weakening region, enabling NVH-optimized current injection. By the application of Vector Space Decomposition (VSD) the electrical quantities are transformed into vector subspaces, which decouples them from the fundamental frequency components, and are subsequently used for tonal noise reduction. In this work, a lumped parameter machine model is chosen and compared with measurements, regarding the formation of the current harmonics. A comparison between radial forces, derived using the analytical winding function approach, corresponding to the three-phase and the asymmetrical six-phase machine is shown. Subsequently, the effect of current harmonics on the noise-critical breathing force-mode is elaborated. For regulating the current harmonics, the VSD control concept is chosen, compared to latest publications and adapted regarding the balancing of the phase currents. FEM simulations, based on statistical experimental design, are performed and subsequent regression curves determine the optimal amplitudes and phases of the current harmonics. These optima are verified on an electrical machine acoustic test bench housing a 250 kW test device, provided by Mercedes-Benz AG. A targeted injection of current harmonics resulting in a reduction of 22 dB in the relevant order of the sound pressure level can be verified in measurements. During the test bench characterization, NVH-optimal feed forward voltage tables for variable speed operation are determined and their influence on efficiency reduction and operating point shift due to additional harmonic torque is evaluated. Furthermore, the potential of using current harmonic injection in a skewed and unskewed rotor design is compared based on test bench measurements.

Institutions

• Institute of Power Electronics and Electrical Drives [614500]
• Chair of Power Electronics and Electrical Drives [614510]