Harmonic Reduction Method for a Single-Phase DC–AC Converter Without an Output Filter

This study suggests a sine-wave modulation technique to achieve low total harmonic distortion (THD) of a buck-boost converter connected to a changing polarity inverter. First, we present the main characteristics of the converter´s topology. Then, we describe how the suggested modulation improves the harmonic content of the output in comparison to the previously used technique, whether harmonics are caused by the inductive nature of the source (e.g., domestic wind turbine) or they are created from external sources at the point the converter is connected (e.g., grid). A prototype was built and the efficiency of the method to tackle harmonics was experimentally verified. Experimental results demonstrate the ability of the method to drastically reduce THD, in comparison with the previous modulation method, so that the output complies with the 5% limit without the use of filters.