Analysis Of Frequency
The coefficients are multiplied with the base switching frequency to provide the operating switching frequency of the inverter, as shown in Fig. 5. It should be noted that the base switching frequency magnitude does not depend on the sub-cycle current ripple variation and is typically adjusted based on operating current, speed and temperature of the traction drive . SIMULATION RESULTS
For the simulation study, a two-level inverter driving a three-phase R-L load is used, as shown in Fig. 7. The proposed approach was tested on a system which operates at a nominal switching frequency of 6 kHz at the linear modulation index range and with 12 kHz at the over-modulation index range. The DC-link voltage …show more content…
The proposed approach was implemented, tested and validated for SVPWM and DPWM2 techniques, including the over-modulation region. The proposed switching frequency variation strategy was able to reduce switching losses up to 20% over the conventional constant switching frequency SVPWM and DPWM2 techniques.
This strategy also spreads peaky harmonic spectrum of the output waveform which may help in reducing acoustic noise, however, consequent introduction of lower frequency harmonics in the spectrum increase current THD which may heat up the motor and the magnet. Thus, in the future study, hardware validation will be done to test the impact of the proposed strategy on the SUMO MD drive system, and an operating region would be defined in which the strategy can be used without any appreciable effect on the motor. REFERENCES
 K. Hayashi and M. Suhama, “Motor driver and methods of controlling the same,” US patent 2011/0193506 A1, Aug. 11, 2011.
 J. W. Kolar, E. R. T. L. Hans, and C. Zach, “Influence of the modulation method on the conduction and switching losses of a PWM converter system,” IEEE Trans. Ind. Appl. VOL. 21, NO. 6, November/December 1991, vol. 21, no. 6, pp. 1063–1075,