Harmonic Analysis of Output Voltage in PWM Inverters

Three-phase two-level pulse width modulation (PWM) inverters have recently been increasing applied due to better performance than thyristor inverters. However, the PWM inverter will bring more high-order harmonics, which may cause the resonance and instability of the power system. Quantitative assessment the effect of PWM strategies on harmonics are significant for system parameter design and filtering. This paper presents a switching angle generation mechanism and calculation method of sinusoidal pulse width modulation (SPWM). Combining the calculated switching angles, the numerical calculation equations based on single Fourier series is derived to perform quantitative evaluation harmonics in SPWM. The proposed method is compared with the method based on classical double Fourier series for computational complexity. The influence of modulation index on each high-order harmonic is summarized. Simulation results are given to validate the correctness of the harmonic quantitative analysis.