Harmonic Emission Level Assessment Considering the Influence of Filters in Harmonic Source Side

Abstract

Evaluation of the harmonic emission levels for a harmonic source at the point of common coupling (PCC) is of major significance for harmonic mitigation. Traditional emission level evaluation methods are based on the assumption that the target harmonic source side impedance (ZH) is far higher than the utility side impedance (ZU). Therefore, only ZU must be calculated during the evaluation process. This assumption is satisfactory for general industrial nonlinear loads. However, for situations in which harmonic filters have been installed on the target harmonic source side, ZH is reduced and may not be far greater than ZU at certain frequencies. In this situation, it is then necessary to obtain the harmonic impedances for both sides at the PCC. However, most existing methods can only calculate ZU. To solve this problem, the complex independent component analysis (ICA) method, which is a widely-known algorithm in this field, is improved in this paper to assess the harmonic emission level accurately when the amplitude of ZH is not much higher than that of ZU. First, a sparse component analysis is introduced into the traditional complex ICA to screen the local signals which are strongly consistent with the true harmonic source signals. Subsequently, a screening mechanism is proposed to screen the local signals again with the objective of non-Gaussian maximization. Finally, using the local signals that are obtained from the two screening processes, we can calculate the harmonic impedances of both sides at the PCC accurately and also evaluate the harmonic emission level.