NDLI: Fundamental grid impedance estimation using grid-connected inverters: a comparison of two frequency-based estimation techniques

Content Provider	IET Digital Library
Author	Mohammed, Nabil Ciobotaru, Mihai Town, Graham
Abstract	With the continuous increase in distributed energy resources that are being integrated into the utility grid, it becomes necessary for inverters to estimate the grid impedance online to be used for several applications. Despite the fact that online grid impedance estimation techniques using grid-connected inverters gained more attention recently, no comprehensive study has been evaluating the performance of different estimation techniques under several grid conditions. This study proposes an extensive comparison to assess the accuracy of two online frequency-based grid impedance estimation techniques at the fundamental frequency. These two techniques are based on the 75 Hz frequency injection technique and pseudo-random binary sequence injection, respectively. Results from MATLAB/Simulink and PLECS RT Box present the advantages and disadvantages of these estimation techniques and the required trade-offs. This comparison study analyses the effects of disturbance magnitude and its injection time, the variation of grid impedance and non-ideal grid voltage. Furthermore, solutions are proposed to enhance the estimation accuracy of both techniques for non-ideal grid voltage containing inter-harmonics and sub-harmonics. The study concludes with recommendations regarding the best use of these two frequency-based grid impedance estimation techniques to suit a particular low voltage grid scenario.
Starting Page	2730
Ending Page	2741
Page Count	12
ISSN	17554535
Volume Number	13
e-ISSN	17554543
Issue Number	Issue 13, Oct (2020)
Alternate Webpage(s)	https://digital-library.theiet.org/content/journals/iet-pel/13/13
Alternate Webpage(s)	https://digital-library.theiet.org/content/journals/10.1049/iet-pel.2019.1458
Journal	IET Power Electronics
Publisher Date	2020-07-30
Access Restriction	Open
Rights Holder	© The Institution of Engineering and Technology
Subject Keyword	75 Hz Frequency Injection Technique Binary Sequences Control of Electric Power System Different Estimation Technique Distributed Energy Resources Distributed Power Generation Estimation Accuracy Frequency 75.0 Hz Frequency-based Estimation Technique Fundamental Frequency Fundamental Grid Impedance Estimation Grid Condition Grid-connected Inverter Harmonics Invertors Nonideal Grid Voltage Online Frequency-based Grid Impedance Estimation Technique Online Grid Impedance Estimation Technique Particular Low Voltage Grid Scenario Power Converter Power Grid Power Supplies to Apparatus Power Supply Quality Power System Control Power System Harmonics Pseudorandom Binary Sequence Injection Statistics Utility Grid
Content Type	Text
Resource Type	Article
Subject	Electrical and Electronic Engineering

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