Experimental determination of inverter losses and sound consequences of using DPWM in an HEV
Paper in proceedings, 2017
This paper presents an experimental determination of the inverter losses and acoustic noise consequences of using discontinuous PWM in a hybrid/electric vehicle application. Acoustic noise and stator vibrations were evaluated using measurements and inverter losses were evaluated both with the use of measurements as well as simulations. The entire operational area for positive torque was covered in the analysis. The results show that the total inverter losses were decreased with about 10-20% when DPWM was used. The introduction of discontinuity in the voltage modulation affects the harmonic content of the phase current. This was further investigated, both electrically and acoustically, focusing on harmonics around the switching frequency, since these are acoustically challenging in the intended application. Measurements show that the magnitude of phase current harmonics around the switching frequency were increased when discontinuous PWM was used. This increase, in the magnitude of these phase current harmonics, amplifies the corresponding harmonics in the stator vibrations which also increased the associated acoustic noise. Therefore, the acoustic noise radiated from the machine and the inverter was enlarged when discontinuous PWM was used. However, the results also show that the adverse acoustic effects were significantly decreased as the machine was operated in the field weakening area.