Identification of excessive harmonic flow in large industrial loads

The application of electronic equipment to industrial facilities has seen an important increase, making the harmonic content of the power flow more difficult to control. When the utility system impedance is subject to variations, the harmonic power flow through the point of common coupling (PCC) can be magnified by resonance phenomena, even in the presence of appropriate harmonic filtering. In this paper, an algorithm is proposed to identify the unacceptable cases of resonance between the customer network and the electric utility power system by calculating the most critical utility system impedance inside a given impedance locus. An optimisation under constraints is carried out for the maximisation of both the voltage and the current distortions of each harmonic at the PCC. The performance indices are then calculated and can reveal the worst cases of excessive harmonic flow through the PCC.