Vector Switching SVPWM Strategy with Spread Spectrum Modulation for PWM Frequency Harmonic Suppression in Three-Level Voltage Source Inverters

This paper presents a vector switching SVPWM (VSSVPWM) strategy for three-level three-phase voltage source inverters (VSIs), which can suppress harmonics near the PWM frequency. On this basis, combined with spread spectrum modulation technology, two comprehensive PWM harmonic suppression strategies are proposed, vector switching random carrier frequency modulation (VSRCFM) and vector switching periodic carrier frequency modulation (VSPCFM), which can further reduce the amplitude of PWM harmonics. Based on the working principle of diode clamped three-level inverters, this paper elaborates on the technical principles and phase voltage harmonic characteristics of conventional three-level SVPWM, VSSVPWM, and comprehensive spread spectrum modulation strategies. This article also explores in detail the impact of the three-level VSSVPWM strategy combined with random spread spectrum and periodic spread spectrum on PWM harmonic characteristics. Finally, simulation and experimental results verified the suppression effect of several proposed strategies on PWM harmonics, and compared the harmonic suppression ability of these strategies under different modulation ratios.