Common Mode Interference Suppression Method for Inverter Based on Markov Process

The fast switching behavior of the power semiconductors in three-phase inverter will bring large common-mode (CM) interference to the electric drive system, which is extremely harmful to the motor and the power grid. To solve this problem, an improved active zero state PWM strategy based on pseudo-random carrier frequency (PRF-AZSPWM3) is proposed. On the basis of no zero vector effect, this strategy simultaneously generates two sawtooth waves and anti-sawtooth waves with the same frequency, and randomly selects a sawtooth wave for combination in each modulation cycle. After being randomly combined, it will no longer be a sawtooth wave in the traditional sense, but an irregular sawtooth wave containing four different modes (sawtooth, anti-sawtooth, triangle, and anti-triangle). At the same time, to generate a random synthetic signal, a two-state Markov chain is employed, so that the carrier frequency changes randomly within a certain range, and the energy content within the harmonics is extended to a greater frequency spectrum. Finally, the effectiveness of the proposed modulation strategy is verified by simulation experiments.