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A New Trapezoidal Modulation Technique to Reduce Acoustic Noise

This paper proposes a new trapezoidal modulation (NTM) technique for systems that use a rechargeable battery and boost converter. A conventional DPWM method can reduce switching loss much more than the sinusoidal PWM method. However, in the DPWM method, the electromagnetic acoustic noise in the motor and reactor increases because the noise containing not only the carrier and its harmonic frequency components but also their sideband components increase significantly. The proposed technique can soften only the part with high voltage change rate in the conventional 120-degree DPWM method. Under the boosting condition, the maximum and minimum values of the voltage references are set to the maximum and minimum values of the carrier. By simulation, the FFT analysis of the line-line voltage with proposed technique shows that the carrier frequency component and its sideband components can be reduced. Furthermore, the reducing effect of the acoustic noise is verified by experiments.