Analyzing and restraining on harmonic of the SPWM inverter

With the increasing of switch frequency, the carrier wave frequency become higher and higher. High switch frequency can enhance the performance and decrease the output filter of power supply system. However, higher switch frequency may also bring about heavy harmonics interference. By analyzing the harmonics of the conventional SPWM inverter, a harmonics suppression method adopted frequency-hopping modulation is proposed in this paper. The carrier wave frequency of the inverter is modulated by using frequency hopping to spread the frequency spectrum and to decentralize the harmonics energy in order to decrease the amplitude of the harmonics obviously. Theoretical analysis and simulation are performed and a 1 KW experimental prototype is designed. Comparative test shows that by using frequency hopping modulation, the harmonic amplitude of the SPWM inverter is about 10 dB lower than the conventional one.