Shaping of the noise spectrum in power electronic converters

Operation of switch-mode converters results in electromagnetic noise propagating throughout the power electronic system. PWM strategies with fixed switching frequency generate harmonics in the spectra of converter voltages and currents. Random pulse width modulation techniques allow elimination of the harmonics, resulting in a continuous spectrum of noise, that is, a spectrum retaining all frequency components. As a next step in advanced spectral shaping, a method presented in this paper produces spectral nulls at selected frequencies. This allows carving communication channels in the noise and removing spectral power at frequencies harmful to the system. Theoretical analysis, computer simulations, and experimental results are presented.