Electric Power ›› 2021, Vol. 54 ›› Issue (3): 109-116.DOI: 10.11930/j.issn.1004-9649.202003086

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A Method for Assessing Harmonic Emission Level of Photovoltaic Access Point Considering System-Side Harmonic Voltage Fluctuations

ZHANG Xu, XU Yonghai, LIU Ziteng, JIANG Haiwei, TAO Shun   

  1. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Source, North China Electric Power University, Beijing 102206, China
  • Received:2020-03-15 Revised:2020-05-20 Online:2021-03-05 Published:2021-03-17
  • Supported by:
    This work is supported by the National Natural Science Foundation of China (No.51777066)

Abstract: With the extensive application of photovoltaic inverter, the harmonic generated during its operation overlaps with the background harmonic of the system at the access point, which causes harmonic amplification and even resonance problems. It is therefore of great significance for the prevention of harmonic problems to evaluate the harmonic voltage emission level of the access point. Different from the traditional non-linear load, the photovoltaic inverter is connected to the power grid after being filtered by filter, which may cause the PV-side harmonic impedance at the point of common coupling (PCC) not to meet the condition of the traditional power grid that requires the PV-side harmonic impedance to be much greater than the system-side harmonic impedance. At the same time, the continuous access of power electronic equipment leads to a large number of harmonics in the system, and the fluctuation of harmonic voltage increases gradually. Therefore, according to the parameters of photovoltaic inverters and filters and the harmonic impedances of the lines, the photovoltaic-side harmonic impedance is estimated firstly. Secondly, the harmonic voltage and harmonic current data of the PCC are classified according to the logistic regression, and the data sets with basically identical background harmonic voltages are selected. And then the system-side harmonic impedance is estimated using partial least square method, so as to reduce the influence of system-side harmonic voltage fluctuation. Lastly, based on the estimation of photovoltaic-side and system-side harmonic impedance, the harmonic voltage emission level is evaluated. Compared with other methods, the proposed method is proved to be superior and accurate.

Key words: photovoltaic, harmonic impedance, harmonic voltage, harmonic emission level, logistic regression