Spectrum Relocation PWM Method for High-power Inverter to Output Specific Interharmonics

A pulse width modulation (PWM) method of specific interharmonic control is proposed for high-power inverters, whose main idea is to use time-shift and phase-shift characteristics of the signal to generate spectrum relocation, and to selectively relocate the specific frequency to the desired interharmonic frequency. Firstly, the mathematical model of phase-shifted modulation is established, the principle of phase-shifted modulation with different modulation sub-periods and amount of spectrum relocation are analyzed, and the amplitude-frequency characteristics of modulation signal are derived. Then, the selective harmonic control based on asymmetric SHE-PWM is used to perform linear phase-shifted modulation on characteristic harmonics and eliminate other adjacent characteristic harmonics at the same time. The spectrum relocation PWM method can be adopted to move the fundamental or characteristic harmonics to adjacent interharmonics and suppress the parasitic interharmonics. Theoretically, the maximum spectrum relocation range is −50~50 Hz. Simulations and experiments show that the spectrum relocation PWM based on asymmetric SHE-PWM is better than the conventional SPWM to control three-phase inverter output specific interharmonics at the switching frequency lower than 1 kHz, and the spectrum relocation PWM based on SVPWM controlling the grid-connected inverter has good specific interharmonic compensation performance. © 2022 Science Press. All rights reserved.