A PWM strategy for acoustic noise reduction for grid-connected single-phase inverters

In grid-connected single-phase inverters, high carrier frequency PWM has been normally applied in the past to obtain a good acoustic performance. With conventional simultaneous switching PWM methods, the current ripples through the inverter output filter inductor are at the carrier switching frequency, which is one of the major causes for inverter's acoustic noise. This paper describes a new PWM strategy using a split switching scheme to increase the inductor current ripple frequency to twice the carrier frequency. Therefore, it is possible to increase the acoustic noise frequency to a sufficiently high level so that the noise is inaudible to the human ears. At the same time, the switching frequency of power semiconductor devices remains relatively low for safe operation and reasonably low switching losses. In addition, this new switching scheme improves the power quality of the inverter output by reducing the current harmonics and dc-link current ripples. Experimental results as presented in this paper have verified the benefits of the proposed PWM strategy.