Analytical and simulation comparison of sinusoidal and resistive modulation strategies for network-friendly three-phase grid-connected inverters

Abstract

The growing numbers of consumers distort AC networks with harmonics. Therefore suppression of the network pollution should be considered. This problem can be solved by using ``network-friendly´´ converters. In our study we examined two modulation strategies of three-phase grid-connected inverters. If these methods are used, converters behave like sinusoidal or resistive current loads of the network, which enables ``network-friendly´´ operation. The examined sinusoidal and the resistive modulation strategies are known, but the differences between the two methods have not been studied before [1,2]. This paper deals with the comparison of these two strategies. First, the analytical examination is presented. By comparing their consumed RMS currents we defined a coefficient (k[%]), which depends only on the total harmonic distortion of the network voltage (THD_u). We demonstrated that at high THD_u resistive modulation method is more favorable. Then simulation examination is discussed, by presenting our model of the three-phase four quadrant converter. Finally simulation results are represented in this article.