Mechanism Analysis of PCC Harmonic Resonance Based on Nonlinear Self-Oscillation Concept in a High-Power Grid-Tied Photovoltaic Plant

Abstract

With the high penetration of photovoltaic systems, the interaction between grid-tied inverters and line impedances results in harmonic resonance at point of common coupling (PCC) in high-power photovoltaic (PV) plants. Thus far, most publications have reported about this issue from a theoretical perspective, and there is no field verification in a real PV plant. To fill this gap, field waveforms are captured in a high-power PV plant to figure out the mechanism of the harmonic resonance phenomenon. This paper, for the first time, presents a nonlinear self-oscillation concept to clarify the mechanism of the harmonic resonance in a high-power PV plant. The field harmonic measurement of a grid-tied PV plant is carried out. The analysis of harmonic spectra and current distributions in a photovoltaic plant shows that these harmonic characteristics are different from the signals generated by the resonances of PV inverter output filters. The correlation of frequency, phase sequence and amplitude show that the different harmonics at PCC are generated by the same source inside PV inverters. Based on the comparison of PCC harmonics with periodic steady-state outputs of nonlinear systems, the nonlinear self-oscillation concept is proposed to clarify the mechanism of the harmonic resonance in a high-power PV plant. The tests in field and signal analysis verify the effectiveness of the proposed method and solution.

Keywords

• grid-tied PV plant
• harmonics resonances
• nonlinear self-oscillation concept