Investigation of Instability in Multiple Grid-Connected Inverters with LCL Output Filters

Fariba Asghari; Arash Safavizadeh; Hamid Reza Karshenas

Investigation of Instability in Multiple Grid-Connected Inverters with LCL Output Filters

Fariba Asghari

Arash Safavizadeh

Hamid Reza Karshenas

Vol. 18, No. 3, pp. 757-765, May 2018

10.6113/JPE.2018.18.3.757

Grid-connected inverter

Harmonic compensator

Proportional-resonant controller

Resonance

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Abstract

This paper deals with the instability and resonant phenomena in distribution systems with multiple grid-connected inverters with an LCL output filter. The penetration of roof-top and other types of small photovoltaic (PV) grid-connected systems is rapidly increasing in distribution grids due to the attractive incentives set forth by different governments. When the number of such grid-connected inverters increases, their interaction with the distribution grid may cause undesirable effects such as instability and resonance. In this paper, a grid system with several grid-connected inverters is studied. Since proportional-resonant (PR) controllers are becoming more popular, it is assumed that most inverters use this type of controller. An LCL filter is also considered at the inverters output to make the case as realistic as possible. A complete modeling of this system is presented. Consequently, it is shown that such a system is prone to instability due to the interactions of the inverter controllers. A modification of PR controllers is presented where the output capacitor is virtually decreased. As a result, the instability is avoided. Simulation results are presented and show a good agreement with the theoretical studies. Experimental results obtained on a laboratory setup show the validity of the analysis.

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Cite this article

[IEEE Style]

F. Asghari, A. Safavizadeh, H. R. Karshenas, "Investigation of Instability in Multiple Grid-Connected Inverters with LCL Output Filters," Journal of Power Electronics, vol. 18, no. 3, pp. 757-765, 2018. DOI: 10.6113/JPE.2018.18.3.757.

[ACM Style]

Fariba Asghari, Arash Safavizadeh, and Hamid Reza Karshenas. 2018. Investigation of Instability in Multiple Grid-Connected Inverters with LCL Output Filters. Journal of Power Electronics, 18, 3, (2018), 757-765. DOI: 10.6113/JPE.2018.18.3.757.