AC-DC Converter with Asymmetrical Higher Harmonics Compensation Function in Sustainable AC Grid

Abstract

In this paper the grid current higher harmonic compensation method for two level AC-DC converters in sustainable AC grid is described. The algorithm is based on Direct Power Control with Space Vector Modulator (DPC-SVM), which was extended by additional Higher Harmonics Compensation (HHC) module. The HHC block is composed of several resonant filters tuned to appropriate frequencies. Both, symmetrical and asymmetrical types of grid currents distortions are analyzed. Operation of the HHC module in stationary αβ coordinates and rotating dq coordinates is discussed. Selected waveforms illustrating operation of the developed algorithm are presented. It is shown that in dq coordinates asymmetrical voltage distortions needs additional effort for its compensation in comparison to symmetrical higher harmonics. The subject is important because in practice asymmetrical higher harmonics usually can appear when one phase nonlinear load is connected to the grid. Even within such conditions the grid connected ACDC converter (GCC) should provide sinusoidal-like current. This assumption provides the reduction of negative impact of the GCC in power quality in Point of Common Coupling (PCC) in sustainable AC grid