Harmonic Injection Method for NVH Optimization of Permanent Magnet Synchronous Motors Considering the Structural Characteristics of the Machine

Noise, vibration and harshness (NVH) is one of the most important performance evaluation aspects of electric motors. Among the different causes of the NVH issues of electrical drives, the spatial and temporal harmonics of the electrical drive system are of great importance. To reduce the tonal noise of the electric motors induced by these harmonics, harmonic injection methods are applied in many applications. However, a lot of existing researches focus more either on improving the optimization process of the harmonic injection parameter settings, or on the controller design of the harmonic injection process, while the structural dynamic characteristics of the motor are seldom considered. A lot of literature shows that the harmonic injection strategies can more effectively influence the mode 0 (M0) radial forces than the higher spatial orders, so it is more efficient to apply such methods at the frequencies/orders where the effect of mode 0 forces are dominant with respect to the surface vibration or acoustics of the motor. In this paper, a guideline is proposed for the design and optimization of current harmonic injection strategies, where a 2-dimensional linear transfer function is computed to quantify the contributions of different force modes and it is used as the reference for the harmonic injection control settings. The proposed method is tested and validated with the multi-physics co-simulation of a finite-element model for an interior permanent magnet synchronous motor (IPMSM), where the influence of the inverter and pulse width modulation (PWM) are also considered and analyzed. The simulation results show that the proposed scheme can effectively reduce the surface vibration (~1.5dB) at the chosen sensor location without deteriorating the torque output performance of the IPMSM model.