What is it about?

The relationship between system stability and resonance of grid-connected inverters is identified in this paper. Moreover, the principle of harmonic amplification of the grid injected current is analysed thoroughly.

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Why is it important?

It is revealed that the resonance is a local concept and the system stability is a global concept. The resonance can arise due to the uncertain grid impedance. The complete resonance will gradually be induced when the stability of the inverter is reduced. And the negative incomplete resonance will arise when the inverter is unstable. Therefore, the system stability and resonance can be unified to some extent. It is found that the cause of harmonic amplification is the low stability of the system, and the lower the stability of the system, the more serious the harmonic amplification. The center frequency of harmonic distribution is where the system has the lowest stability. Therefore, in order to reduce the harmonic content of the grid injected current, the system requires sufficient stability margin.

Perspectives

The above research work is meaningful for the next study. It tells us a fact that the stability, resonance and harmonic amplification of the system can be unified to some extent. In order to reduce the harmonic content of the grid injected current and avoid the complete resonance and negative incomplete resonance, the system requires sufficient stability margin. Therefore, we are going to focus on improving the stability of grid-connected inverters under weak grid.

Bao Xie
Chongqing University

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This page is a summary of: Analysis of resonance and harmonic amplification for grid-connected inverters, IET Generation Transmission & Distribution, February 2019, the Institution of Engineering and Technology (the IET), DOI: 10.1049/iet-gtd.2018.6499.
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