Identification of Harmonic Source at the Point of Common Coupling Based on Voltage Indices

Abstract

Kertas kerja ini membentangkan teknik baru untuk mengesan punca gangguan harmonik, samada pembekal atau pengguna. Dalam kaedah ini, litar–litar setara Norton dan Thevenin diperolehi untuk tujuan pengesanan punca gangguan harmonik. Berdasarkan kedua–dua litar setara tersebut, dua kes telah dianalisa iaitu litar yang mempunyai satu punca harmonik dan litar yang mempunyai dua punca harmonik. Di dalam litar yang mempunyai satu punca harmonik, litar setara diringkaskan kepada litar setara Thevenin untuk memperolehi indeks voltan. Voltan yang diperolehi di titik gandingan sepunya (TGS) dibandingkan dengan voltan di pihak pembekal. Di dalam litar yang mempunyai dua punca harmonik, teorem tindihan dan litar setara Norton digunakan untuk menerbitkan indeks voltan daripada bacaan yang diperolehi di titik gandingan sepunya. Beberapa kes dan ujian suis dijalankan menggunakan perisian PSCAD/EMTDC. Perbandingan dilakukan dengan teknik galangan kritikal (GK) untuk membuktikan kesahihan teknik yang dicadangkan dalam pengesanan punca gangguan harmonik. Keputusan yang diperolehi membuktikan teknik pengesanan punca gangguan harmonik berdasarkan indeks voltan lebih baik daripada teknik galangan kritikal (GK). Kata kunci: Harmonik, teorem tindihan, galangan harmonik 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 identificafion. 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. Key words: Harmonic, superposition theorem, harmonic impedance