Comment on “Impact of Load Frequency Dependence on the NDZ and Performance of the SFS Islanding Detection Method”

International audienceWe read with interest an article [1] published in the IEEE Transactions on Industrial Electronics in 2011 and tried to reproduce the results of this article for the needs of our own research. Unfortunately, we were led to think that the load model equations used by the authors contained an inconspicuous but significant mathematical error, leading to erroneous results and conclusion. The present paper brings a correction to some figures and their analysis as well as the paper conclusion. The new results show that the load's frequency dependence has actually no significant impact on the NDZ of the SFS method. Index Terms—Distributed generation (DG), inverter, islanding detection, Sandia frequency shift (SFS)

A survey of islanding detection methods for microgrids and assessment of non-detection zones in comparison with grid codes

Detection of unintentional islanding is critical in microgrids in order to guarantee personal safety and avoid equipment damage. Most islanding detection techniques are based on monitoring and detecting abnormalities in magnitudes such as frequency, voltage, current and power. However, in normal operation, the utility grid has fluctuations in voltage and frequency, and grid codes establish that local generators must remain connected if deviations from the nominal values do not exceed the defined thresholds and ramps. This means that islanding detection methods could not detect islanding if there are fluctuations that do not exceed the grid code requirements, known as the non-detection zone (NDZ). A survey on the benefits of islanding detection techniques is provided, showing the advantages and disadvantages of each one. NDZs size of the most common passive islanding detection methods are calculated and obtained by simulation and compared with the limits obtained by ENTSO-E and islanding standards in the function of grid codes requirements in order to compare the effectiveness of different techniques and the suitability of each one

Anti-Islanding Techniques for Integration of Inverter-Based Distributed Energy Resources to the Electric Power System

The emergence of microgrids and the increasing adoption of Distributed Generation Systems (DGS) have created an opportunity to replace traditional fossil fuels with renewable resources. Such a shift poses security and power quality challenges that must be addressed by academics and industrial research paradigms. Unintentional islanding is an important security concern, as it can result in power quality degradation, electrical hazards, and equipment damage. To address this problem and find efficient solutions, many anti-islanding techniques to detect and eliminate the phenomenon can be found in the specialized literature. These solutions can be classified as passive, active, remote, hybrid, or based on machine learning and signal processing techniques. In this context, this paper provides a comprehensive review of existing anti-islanding methods, highlighting their importance in preventing dangerous situations. The review includes a detailed analysis of the advantages and limitations found for each method, as well as its suitability for practical applications. The goal is to provide a valuable resource for researchers and practitioners in the field of distributed power systems, enabling them to choose the most appropriate anti-islanding method for their specific needs. Overall, this paper aims to address the challenges posed by unintentional islanding and promote the adoption of renewable energy resources for a more sustainable future.© 2024 The Authors. This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/fi=vertaisarvioitu|en=peerReviewed

An Islanding Detection Method for Micro-Grids With Grid-Connected and Islanded Capability

With the increasing prevalence of renewable energy and distributed generation (DG) in distribution systems, micro-grids are becoming more popular and an attractive option for enhancing system operation and reliability. This can be attributed to the micro-grid ability to operate in both connected and disconnected modes. Equally important, micro-grids are the best solution to meet the increasing demand of electric power in a cost effective manner due to the close proximity to the load demand and thus minimizing system losses. Islanding detection methods have been proposed for inverter based distributed generation with only grid-connected capability. Micro-grids are composed of DGs that are capable of operating in two modes: grid connected and islanded. This thesis introduces and proposes the concept of micro-grid transition detection where the status of the micro-grid is detected based on adaptively modifying the droop slope. The droop coefficient is chosen such that the micro-grid is stable while grid connected and in the contrary Unstable once an islanded micro-grid operation is initiated. The droop coefficient is adaptively modified, once the micro-grid transitions from grid-connected to islanded operation, to stabilize the micro-grid for the islanded mode of operation. The proposed method is capable of detecting micro-grid transition in less than 600 ms under various active and reactive power mismatches. The proposed micro-grid transition detection method is tested on a micro-grid equipped with inverter based DGs controlled using the droop approach. The main objective of this thesis is to develop a novel islanding detection method for micro-grids with grid connected and islanded capability. A micro-grid model was developed using power system computer aided design/ electromagnetic transient and DC (PSCAD/EMTDC) as a platform for testing the proposed method. Simulation results were conducted considering the Institute of Electrical and Electronics Engineers Standard 1547(IEEE Std. 1547) standard islanding detection testing procedure

Unintentional Islanding in Distribution Networks with Large Penetration of Power Electronics and Renewable Energy Systems

The PhD thesis focus on the analysis and investigation of a crucial issue related to increasing number of distributed energy resources (DERs). This recent issue is the unintentional (i.e. uncontrolled) islanding operation in distribution network with large penetration of DERs based on power electronic converters. Particular focus has been addressed to the interaction between DERs, protection systems and new connection rules required by standard bodies. The aim of the research activity is the investigation on the causes and the influencing factors of unintentional islanding in medium and low voltage (MV and LV) distribution network. The unintentional islanding issue has interested many studies and publications over the last decades. However, the literature research is lacking of considering the lately introduced European standards and technical specifications for DERs. Therefore, during the PhD research, novel aspects of how requirements and ancillary services influence the unintentional islanding operations have been studied, highlighting novel relevant factors, such as the role of the loads characteristics, the influence of the frequency measure and the inverter regulation speed

Transient And Distributed Algorithms To Improve Islanding Detection Capability Of Inverter Based Distributed Generation

Recently, a lot of research work has been dedicated toward enhancing performance, reliability and integrity of distributed energy resources that are integrated into distribution networks. The problem of islanding detection and islanding prevention (i.e. anti-islanding) has stimulated a lot of research due to its role in severely compromising the safety of working personnel and resulting in equipment damages. Various Islanding Detection Methods (IDMs) have been developed within the last ten years in anticipation of the tremendous increase in the penetration of Distributed Generation (DG) in distribution system. This work proposes new IDMs that rely on transient and distributed behaviors to improve integrity and performance of DGs while maintaining multi-DG islanding detection capability. In this thesis, the following questions have been addressed: How to utilize the transient behavior arising from an islanding condition to improve detectability and robust performance of IDMs in a distributive manner? How to reduce the negative stability impact of the well-known Sandia Frequency Shift (SFS) IDM while maintaining its islanding detection capability? How to incorporate the perturbations provided by each of DGs in such a way that the negative interference of different IDMs is minimized without the need of any type of communication among the different DGs? It is shown that the proposed techniques are local, scalable and robust against different loading conditions and topology changes. Also, the proposed techniques can successfully distinguish an islanding condition from other disturbances that may occur in power system networks. This work improves the efficiency, reliability and safety of integrated DGs, which presents a necessary advance toward making electric power grids a smart grid

Analysis of active islanding detection methods for grid-connected microinverters for renewable energy processing

[EN] This paper presents the analysis and comparison of the main active techniques for islanding detection used in grid-connected microinverters for power processing of renewable energy sources. These techniques can be classified into two classes: techniques introducing positive feedback in the control of the inverter and techniques based on harmonics injection. Accurate PSIMTM simulations have been carried out in order to perform a comparative analysis of the techniques under study and to establish their advantages and disadvantages according to IEEE standards.This work was supported by the Spanish Ministry of Science and Innovation under Grant ENE2009-13998-C02-02.Trujillo Rodríguez, CL.; Velasco De La Fuente, D.; Figueres Amorós, E.; Garcerá, G. (2010). Analysis of active islanding detection methods for grid-connected microinverters for renewable energy processing. Applied Energy. 87(11):3591-3605. https://doi.org/10.1016/j.apenergy.2010.05.014S35913605871

Investigation of the stability of the anti-islanding detection in multi-DGs system

U radu je predstavljen poboljšani model multi-DGs mikro rešetki za analizu stabilnosti sustava tijekom vezivanja s rešetkom. DGs u sustavu opremljeni su Sandia frequency shift (SFS) shemom kao načinom anti-islanding zaštite. Uvođenjem dužine linije distribucijske mreže, pozitivnog porasta povratne sprege SFSa i distribuiranog dovoda energije, parametri izlazne snage za poboljšanje matematičkog modela mikro energetskih rešetki uspostavljeni su u tri vrste parametara i odnosu između margine stabilnosti mikro energetske rešetke za postizanje stabilnosti sustava praga dužine linije energetske mreže, i stabilnosti granične vrijednosti napona izlazne snage distribuirane istosmjerne struje. Taj postupak omogućuje projektantima i inženjerima obnovljivih energetskih sustava optimiziranje sustava i osiguranje stabilnosti. Konačno, uzimajući u obzir nekoliko potvrđivanja simulacija, u radu se daje poboljšani model koji može utjecati na aktualnu implementaciju analize distribuirane mikro energetske rešetke, te se tako može donijeti zaključak o stabilnosti kritičkog praga parametara sustava. Na temelju tih analiza slučaja, pokazalo se da je stabilnost sustava vrlo važna za stabilnost mikrorešetki mnogih distribuiranih multi-DGs, koji su korisni za projektiranje i implementaciju novih energetskih sustava.This paper presents an improved model of multi-DGs microgrids for analysing system stability during grid-connections. The DGs-in the system are equipped with the Sandia frequency shift (SFS) scheme as an anti-islanding protection technique. By introducing a distribution network line length, SFS positive feedback gain and distributed power supply, power output parameters to improve the micro power grid mathematical model are established in three kinds of parameters and the relationship between micro power grid stability margin, to obtain stability of the system of power line length threshold, and stability of the distributed power dc output voltage threshold. This process allows the designers and engineers of renewable energy systems to optimize the system and ensure stability. Finally, in view of the several common simulation validations, this paper puts forward an improved model that can affect actual implementation of distributed micro power grid analysis, whereby the stability of the system parameters’ critical threshold may be deduced. Based on these case studies, system stability is shown to be very important to the stability of many distributed multi-DGs microgrids, which are useful for the design and implementation of new energy systems