Suppressing the Maximum EMI Spectral Peak Through Asynchronous Carriers in the Three-Phase Inverter With the Periodic CFM

In inverters, high-frequency switching of pulsewidth modulation is the main source of electromagnetic interference (EMI). The carrier frequency modulation (CFM) technology can effectively reduce the spectral peaks of EMI. This letter proposes an asynchronous carrier scheme. In the scheme, the carrier frequencies of three legs are staggered from each other to avoid the possibility of superposition, which will appear by using the same carrier in the three-phase inverter. Based on the suppression of the spectral peaks in the periodic CFM, the use of the asynchronous carriers will further disperse the EMI peak energy. The case that the maximum EMI spectral peak is suppressed to the lowest is sought out under some given parameters. The feasibility and effectiveness of the asynchronous carrier scheme are verified by the simulations and experimental results in a three-phase inverter.