Photovoltaic grid-connected multi-inverter system resonance observation method based on node mapping

Abstract

The invention discloses a photovoltaic grid-connected multi-inverter system resonance observation method based on node mapping, comprising three parts: detecting the resonance frequency, determining aresonance center and evaluating the participation degree of each element. A network node admittance matrix is constructed based on a multi-inverter system node mapping model; feature values and feature vectors of the matrix are calculated, an approximate singular matrix is searched, and the reciprocals of the feature values and the frequency spectrum curve of frequencies are output; and the participation factor of each node under each resonant frequency is calculated, the position of the resonance center is determined, the resonance sensitivity of the nodes is compared, the sensitivity of each element is analyzed, and the resonance participation degree of each element is evaluated. According to the method, comprehensive resonance condition analysis can be carried out on a photovoltaic grid-connected multi-inverter system, the harmonic resonance analysis efficiency of the system is improved, a basis can be provided for the topological design and element type selection of a photovoltaicpower station, and a foundation can be laid for the research of a resonance suppression strategy.

Description

technical field [0001] The invention belongs to the technical field of power system analysis and control, in particular to a node mapping-based photovoltaic grid-connected multi-inverter system resonance observation method. Background technique [0002] The world's energy industry is undergoing major changes, the situation of fossil energy is becoming increasingly severe, and the new energy industry in various countries is developing rapidly. In 2018, my country's newly added photovoltaic grid-connected installed capacity was 44.26GW, ranking first in renewable energy, and the cumulative photovoltaic installed grid-connected capacity reached 174.46GW. Photovoltaic power stations in my country are mainly concentrated in remote areas such as the Northwest, and the long-distance transmission lines make the grid impedance cannot be ignored. When the photovoltaic grid is connected, multiple inverters are usually connected in parallel through a common connection point, and the gr...

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Problems solved by technology

[0003] In recent years, LCL filters have been more and more used in photovoltaic grid-connected inverters, but LCL filters are underdamped third-order systems, and there are resonance peaks themselves, which will affect the stability of the system

Under the condition of weak grid, due to the increasing application of photovoltaic access and power electronic devices, as well as factors such as LCL filter, phase-locked loop, multi-inverter and grid interaction, and dynamic interaction between multi-inverters, photovoltaic parallelism The grid multi-inverter system will be coupled into a complex high-order network, which will easily cause harmonic resonance problems, degrade power quality, and threaten the safe and stable operation of the system

[0004] However, the spectrum method is generally used to observe the resonance of the power system. This method can accurately determine whether the resonance occurs and obtain the resonance frequency, but it is difficult to give more comprehensive and deeper resonance information, and the steps are complicated and the detection speed is slow.

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