IDENTIFICATION OF HARMONIC SOURCE AT THE POINT OF COMMON COUPLING BASED ON VOLTAGE INDICES

This paper presents a new method to determine harmonic source either at the utility or the customer based on voltage indices. In the method, both Thevenin and Norton equivalent circuits are first derived for harmonic source identification. Based on these circuits, two cases are analyzed, that is a circuit with a single harmonic source and a circuit with two harmonic sources. In a single harmonic source, harmonic circuit is simplified to a Thevenin equivalent circuit which is used to derive the voltage indices. The voltage measured at the point of common coupling (PCC) is compared with the voltage at the utility sides. In a two harmonic source system, the superposition theorem and Norton equivalent circuits are employed to derive the voltage indices at utility and customer sides based on the voltage and current measurements at the PCC. For both systems, the voltage index based on the higher voltage magnitude is identified as the main harmonic source. Several case studies and a series switching tests are performed in the simulations using the PSCAD/EMTDC program. Comparisons are made with the Critical Impedance (CI) method to verify the accuracy of the proposed method in harmonic source identification. Results proved that the identification of harmonic source at the point of common coupling based on voltage indices is more accurate when compared to the CI method.