Study Of Harmonic Responsibility Quantitative Calculation Method And Evaluation Indices

With the wide application of the nonlinear power electronic devices and many distributed power connected to grid by the inverters, harmonic distortion has captured the attention of many researchers. As we all know, the harmonic pollution is generated by the interaction of a number of nonlinear loads in power system with wave distortion. For the customer with non-linear loads, how to distinguish the harmonic responsibility between it and the supply system at the point of common coupling (PCC), is the key premise for harmonic pollution economic rewards and punishments and governance. At present, the study for this aspect is still in its infancy at home and abroad.Before allocating the harmonic contributions between the customer and the supply system at PCC, the very first question is that which evaluation indice we should adopt. Firstly, this paper summarizes several traditional harmonic responsibility assessment indices and analyzes their existing problems and disadvantage, thus draws forth two basic questions for harmonic responsibility quantitative calculation, namely, the equivalent circuit of harmonic analysis and the principle of harmonic responsibility allocation. Then, the supply system side is equivalent to the Thevenin model and it adopts the mixed total least squares (LS-TLS) method to estimate the equivalent parameters with the synchronous harmonic voltage and harmonic current at PCC; Contrast to the complex least squares method, when the harmonic data have a big error, the mixed total least squares method could get more accurate results. On the other hand, the customer side is equivalent to the Norton equivalent circuit, get its fundamental impedance by the fundamental voltage and current at PCC and get its harmonic current source in parallel by the harmonic voltage and current at PCC. Finally, according to the equivalent circuit for harmonic analysis and the principle of superposition, the physical meaning of harmonic responsibility allocation at PCC is clear and the principle of harmonic voltage and current responsibility allocation is redefined based on the amplitude weighted, and further puts forward new evaluation indices, which include the restriction indices(individual harmonic voltage ratio or harmonic current emission values)^ the equipment capacity occupancy index(responsibility index of the nonfundamental apparent power) and harmonic energy loss index, the overall process of harmonic responsibility quantitative assessment is presented at last.Based on IEEE 14-bus test system by PSCAD/EMTDC, the results and comparisons of case studies demonstrate that, the parameters calculation methods for the equivalent circuit of supply system side and customer side have high accuracy and the equivalent circuit model is suitable for harmonic responsibility allocation; All of these quantitative evaluation indices can illustrate the specific meaning of harmonic responsibility more comprehensively and reasonably, which have important guiding significance for engineering practice and great application value.