Time-domain harmonic source location and evaluation methods based on non-linear and time-varying properties of devices

Most of the existing methods for harmonic analysis are from frequency-domain perspective. In fact, the essential factor for generating harmonics is non-linear characteristic or time-varying property. Therefore, the harmonic generation mechanism and the harmonic source location method are investigated from the time domain perspective in this paper. Firstly, a general model of non-harmonic sources is established. The non-harmonic sources will match well with the proposed general model while the harmonic source will not. Then correlation coefficient that reflects compliance degree between each device and the general model is defined for distinguishing harmonic sources from non-harmonic sources. On this basis, a novel time-domain harmonic source location method is proposed. Numerous simulations and experiments have demonstrated that the proposed method has good performance under fluctuations, saturations, pre-distortions, transient process, and resonances. The defined correlation coefficient can reflect non-linearity/time-varying degree of the harmonic source, which can be used for evaluating harmonic emission level of each harmonic source. On this basis, a simple harmonic responsibility division method is proposed, which is immune to possible fluctuations, pre-distortions, saturations, resonances, and impedance variation.