On active anti-islanding techniques: survey

Indonesian Journal of Electrical Engineering and Computer Science Vol. 22, No. 2, May 2021, pp. 609~618 ISSN: 2502-4752, DOI: 10.11591/ijeecs.v22.i2.pp609-618  609 On active anti-islanding techniques: survey Y. A. Elshrief1, Sameh Abd-Elhaleem2, B. A. Abo Zalam3, A. D. Asham4 1,4 Egyptian Academy for Engineering and Advanced Technology (EAE & AT), Ministry of Military Production, Egypt 2,3 Faculty of Electronic Engineering, Menoufia University, Egypt Article Info ABSTRACT Article history: The phenomenon of feeding loads from any distributed generators (DGs) with a total disconnection of utility grid at the point of common coupling is called islanding. The DGs are usually independently controlled. Hence, when the islanding problem occurs, the electric utility loses the control and supervision over that section of the power grid. Furthermore, prolonged islanding can prevent reconnection to the power grid and may cause damage due to voltage and frequency excursions. Therefore, the islanding detection, which is also called anti-islanding (AI), is one of the most critical aspects of the integration of DG sources into the power grid. In this paper, a comprehensive survey on the local AI techniques is illustrated, especially active type which is used for improving the performance regarding the size of the non-detection zone and detection speed. Extensive comparisons are provided to demonstrate the effectiveness of each technique. Received Oct 4, 2019 Revised Mar 17, 2021 Accepted Mar 27, 2021 Keywords: Anti-islanding Distributed generation Grid-connected Islanding detection Photovoltaic Power quality This is an open access article under the CC BY-SA license. Corresponding Author: Yasser Ahmed Elshrief Department of Electrical Engineering Egyptian Academy for Engineering and Advanced Technology (EAE & AT) Ministry of Military Production, Egypt Email: 1. INTRODUCTION Increasing the demand of energy over the world and in addition to the limited resources for traditional power generation methodologies, different distributed generators (DGs) resources such as wind turbines, solar energy, fuel cells, water turbines and micro-turbines, are utilized in modern distribution systems [1], [2]. As shown in Figure 1, the DG source at the end users generates a reverse power flow at the utility side which will affect the protection of utility. Nevertheless, sources of DG have been become increasingly popular because of its ability to solve several issues associated with conventional power systems [3]. The DG sources are distinguished by reduceing the demand on the transmission system, where the DGs are distributed near the load so, the reliability of the power grid is increased. Furthermore, the DGs have a lot of benefits such as reducing power losses, improving the voltage profile, enhancement of power quality (in some cases) [4]. On the other hand, some disadvantages affect the safety of the utility grid and the main dangerous problem is the islanding which is considered an undesirable phenomenon leads to power quality problems for the customer’s loads, safety hazards for the humans which are working for maintenance the utility. In addition to, the islanding can cause a change in the fault level, frequency and voltage control problems, and power supply facilities as a result of unsynchronized recloser and damage to power generation [1]-[3]. Hence, according to the IEEE standards, this phenomenon should be detected within less than 2s. As shown in Figure 2, the islanding phenomenon happens in conjunction with opening of the circuit breaker (CB). The entire left side includes the generation and loads become isolated and the solar generation Journal homepage: http://ijeecs.iaescore.com 610  ISSN: 2502-4752 system continues to energize these isolated loads. This situation degrades the quality of power and creates an unsafe condition in the system. (a) Traditional distribution system (b) Modern distribution system Figure 1. Power distribution system (traditional and modern) Figure 2. Model of a grid-disconnected DG source (islanding phenomenon) There are two main techniques which are used for detecting islanding phenomenon, the remote and the local techniques, where the local technique is divided into passive and active as shown in Figure 3. The basic idea of the remote techniques is illustrated as shown in Figure 4 by transmitting a low-energy signal continuously between the transmitter (T) founded in the grid side and the receiver (R) founded in the DG side. When this communication is failure, the receiver sends a stopping signal to the inverter and/or a switch (included in the receiver) should be opened for isolating the load from the DG [5]. Figure 3. Classification of Islanding Techniques Figure 4. The general structure of the remote AI technique The advantages of this technique are the output power quality of the inverter is not decreased, the ability of working in areas with high density of DG, it does not have non-detection zone (NDZ) and doesn't depend on the system size. Moreover, there some disadvantages such as the receiver and transmitter cost may be too high, it requires multiple signal generators and this has a high cost in comparison with a simple radial Indonesian J Elec Eng & Comp Sci, Vol. 22, No. 2, May 2021 : 609 - 618 Indonesian J Elec Eng & Comp Sci ISSN: 2502-4752  611 system, under abnormal conditions it has NDZ if some loads are operating. It needs a reliable communication system [5], [6] which requires enormous infrastructure and hence, extremely excessive cost. Consequently, these techniques are rarely used on a small scale. This paper surveys the recently developed AI techniques applicable to inverter-based DG sources which are the largest and the fastest-growing sector [6]. The survey is organized as follows: The issue of islanding is discussed in Section two. Comparative AI techniques and the advantages and disadvantages for each technique especially the problem of NDZ and the impact of them on the power quality are presented in Section three. Finaly, the conclusion and an outlook for future research in this area is collected in Section four. 2. ISSUES OF ISLANDING Intentional islanding is occurred by humans, who have authority on the system for maintenance or emergencies, but there is unintentional islanding that is happened without any interference from humans; both cases have many disadvantages as listed, a) safety issues arise for all humans who are working on the line, where they could have hazards as a result of the generated power from DG sources in case of the disconnection of power from a utility grid, b) the values of frequency and voltage may vary away from the standard permissible level, and c) unintentional reclosing may lead to a desynchronization of DG, which causes unexpected mechanical torque can destroy the generators [4]. Based on what has been put forward and the previous shortcomings, islanding must be d (...truncated)