Space Spread-Spectrum-Based PSC-PWM for MMC to Reduce Conducted CM EMI

Modular Multilevel Converter used in high- voltage direct current transmission is prevalent nowadays. However, with quantities of IGBT modules, MMC becomes the natural source of Electromagnetic Interference. This paper puts forward a novel strategy called Space Spread-Spectrum-based Carrier Phase-Shifted PWM for MMC to reduce conducted common-mode EMI. This paper analyzes the principle of Space Spread-Spectrum with Double Fourier Transform, which deduces Space Spread-Spectrum-based Carrier Phase-Shifted PWM can change the harmonic from one high amplitude Nf
c
+nf
0
frequency spike pulse to N low amplitude Nf
c
+iNΔf+nf
0
frequency harmonics. Space Spread-Spectrum needs to follow several principles. The carrier frequency variation of corresponding submodules of the upper and lower bridge arm should be consistent. Spectrum should spread evenly and the frequency variation should not exceed f
c
/N. Simulation and experiment shows the good effect of Space Spread-Spectrum, which reduce the conducted common-mode Electromagnetic Interference about 10dB.