Islanding Phenomena Research Articles

A critical assessment of islanding detection methods of solar photovoltaic systems

This study identifies inadvertent islanding in electrical networks incorporating Distributed Generators (DGs). With the global rise of DG deployment, it becomes imperative to scrutinize their influence on the network and guarantee that anti-islanding protective systems can accurately discern such conditions. However, it is equally important to prevent false alarms that might result in unwarranted DG disconnections during unrelated incidents. Fulfilling these stringent technical prerequisites is a fundamental aspect of ensuring the safe and dependable functioning of the electrical grid. Consequently, this investigation aims to comprehensively explore the scholarly discourse surrounding islanding detection methodologies for distributed generators. The manuscript assesses various methods for detecting islanding phenomena, spanning passive, active, and remote techniques. These include under/over voltage, Sandia frequency/voltage shift, Sandia frequency shift, and under/over frequency protection mechanisms. It offers an exhaustive review of diverse techniques to identify islanding in distributed generation networks, studying their respective merits, demerits, and overall efficacy in pinpointing this condition. Thus, this research holds paramount importance in bolstering the dependability of electrical networks incorporating DGs. It aids in advancing anti-islanding protection systems that satisfy crucial technical specifications.

A Novel Approach for Secure Hybrid Islanding Detection Considering the Dynamic Behavior of Power and Load in Electrical Distribution Networks

In the arena of modern electrical power distribution systems, distributed generators (DGs) are emerging as a manifestation of electric power personalization. Even though DGs have various advantages, unintentional islanding phenomena caused by DGs during abnormal grid operations can damage equipment connected to the grid. Therefore, islanding detection mechanisms are essential for DGs in grid-connected mode to disconnect the DG from the grid in case of grid abnormalities by obeying to specific grid codes. In this regard, a novel approach to develop a secure hybrid islanding detection method (IDM) is presented in this paper. The proposed hybrid IDM is developed by combining two passive IDMs known as rate of change of active power and rate of change of reactive power with an active IDM called load connecting strategy. An 11 kV Malaysian distribution system integrated with three types of DGs, namely synchronous generator, photovoltaic, and biomass, has been chosen as a testbed for the verification of the proposed hybrid IDM. Seven different case studies have been conducted in the PSCAD/EMTDC platform to validate the performance of the proposed IDM for islanding and non-islanding events. The simulation results confirm that the proposed IDM can detect islanding within 0.09 s, which is within 2 s complying with IEEE and IEC standards. Further, a comparative study based on the detection time and non-detection zone has been carried out, which has confirmed that the proposed IDM demonstrates better performance compared to the previously developed hybrid IDMs.

Hybrid islanding detection technique for distribution network considering the dynamic behavior of power and load

AbstractNowadays, distributed generation (DG) has become an indispensable part for meeting the growing power demand in electrical power generation and distribution. However, one of the drawbacks of DG is unintentional islanding phenomena, which has become a safety issue for both human and equipment connected to the system. To prevent this hazardous condition, according to IEEE 1547 standards, this islanding condition must be detected within 2 s. This paper proposed an approach to develop a hybrid islanding detection method (IDM) to prevent the damages caused by this islanding condition. The proposed hybrid IDM is a combination of three different IDMs, two passive and one active; that is, rate of change of active power (ROCOAP) and rate of change of reactive power (ROCORP) are passive IDMs where load connecting strategy (LCS) is active. To differentiate islanding conditions with similar occurrences, different case studies are taken into account with photovoltaic (PV) and synchronous generator (SG) working as distributed generators on PSCAD/EMTDC platform. The simulation results confirm that proposed IDM is more favorable compared to other IDMs due to simplicity and fast islanding detection time when its performance is tested on the 11‐kV Malaysian distribution system for various cases.

Superimposed Impedance-Based Passive Islanding Detection Scheme for DC Microgrids

Due to improved efficiency, reduced conversion stages, integration of distributed generators (DGs), and increased use of DC loads, DC microgrids (MGs) are earning extensive approval in modern power grids. Islanding detection is a critical issue for both AC and DC MGs. If the detection technique fails, it may lead to instability in the system, affecting the load-side devices and employees. Therefore, this article aims for the development of a novel passive islanding detection scheme (IDS) based on the cumulative sum of superimposed impedance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CSOSI</i> ) for DC MGs. In the proposed IDS, voltage and current samples are collected at DGs terminals to analyze a DC MG response for an islanding condition. Superimposed impedance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SI</i> ) and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CSOSI</i> are calculated, and the variations in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CSOSI</i> are measured to detect islanding phenomena. The proposed passive IDS is simulated using MATLAB/Simulink environment, and the experimental validation is accomplished on a DC MG hardware setup. The obtained results depict that the proposed technique effectively discriminates islanding events from other nonislanding scenarios and acts effectively during islanding scenarios for radial and ring-type systems irrespective of the type and number of DGs present in the DC MGs. The effectiveness of the proposed scheme is also tested for both constant resistance and constant power loads.

Islanding Detection of Synchronous Generator-Based DGs using Rate of Change of Reactive Power

The question of the islanding operation of distributed generations (DGs) and that of the current inadmissible networking policy of islanding operations sets a demanding task for an efficient islanding detection, preferably from a single place, using either passive or active islanding-detection method. Islanding detection shall be faster than the fast automatic reclosing of the connected transmission line connected to the DG unit. This paper deals with the detection method of islanded operation mode for the large power synchronous generator-based DGs in bio-mass power plants. The proposed method has been applied to a practical 10-MW bio-mass power plant and experimentally tested to verify the simulation results. The rate of change of reactive power ( dQ/dt >) criterion is derived as a yardstick for islanding detection. The practical power plant model has been implemented to be simulated in DIgSILENT PowerFactory and MATLAB/Simulink software environments. Offline digital time-domain simulations and experimental tests on a practical bio-mass power plant reveals that the proposed method efficiently, and authentically detects islanding phenomena with high accuracy, low detection time, very small number of non-detected zones and, with almost zero power balance ( ΔP = 0).

The Integrated Switching Control Strategy for Grid-Connected and Islanding Operation of Micro-Grid Inverters Based on a Virtual Synchronous Generator

In allusion to the virtual synchronous generator (VSG)-based voltage source inverters in micro-grids, an integrated control method combining a quasi-synchronization algorithm and an islanding detection algorithm is proposed to improve the power supply reliability and quality, which can simultaneously meet the operational requirements of both grid-connected mode (GCM) and off-grid mode (OGM), and the smooth switching between them. The quasi-synchronization algorithm of the micro-grid inverter is designed to realize a flexible grid connection. Moreover, for quickly detecting islanding phenomena, a novel islanding detection algorithm based on the VSG’s inherent characteristics is put forward. Finally, the validity and availability of the proposed models and control strategies are comprehensively verified by simulation results based on Matlab/Simulink.

A novel islanding detection technique for grid connected photovoltaic system

Islanding detection is the major issue in Grid Connected Photovoltaic (PV) System and still it remains a challenge for researchers to interconnect the PV system with the Grid. The algorithms which are listed in the literature are failed to identify the Islanding phenomena for the several source configuration. In this paper a novel islanding detection technique is presented to reduce the non-detection zone (NDZ) at the point of common coupling (PCC) and it can be widely used for various renewable energy system configurations. The simulations have been carried out in Matlab/Simulink for several test conditions. The simulations results are presented to confirm the effectiveness of the proposed method.

Islanding Detection in Photo-Voltaic Systems Based on Instantaneous Power Measurements

Today, renewable and clean energy sources are being used to generate electric power and to reduce dependency on conventional fossil fuels, which are limited in supply and cause immense pollution. Renewable energy is also a sustainable type of energy. Although it may not be a cost-effective type of energy in the short term, it can contribute to reducing greenhouse gas emissions. Safety operations and measures are of great concern, and the prevention of islanding phenomena plays an important role for areliable energy system. Therefore, anti-islanding protection is a requirement for connecting to the utility grid. Here, we propose a different and fast method for islanding detection in photo-voltaic (PV) systems. The suggested method is based on instantaneous power calculation at the point of common coupling and is able to detect islanding conditions within a few sampling intervals. No further calculations are needed to detect islanding problems for grid-connected PV systems.

Comparative Study of Advanced Signal Processing Techniques for Islanding Detection in a Hybrid Distributed Generation System

In this paper, islanding detection in a hybrid distributed generation (DG) system is analyzed by the use of hyperbolic S-transform (HST), time-time transform, and mathematical morphology methods. The merits of these methods are thoroughly compared against commonly adopted wavelet transform (WT) and S-transform (ST) techniques, as a new contribution to earlier studies. The hybrid DG system consists of photovoltaic and wind energy systems connected to the grid within the IEEE 30-bus system. Negative sequence component of the voltage signal is extracted at the point of common coupling and passed through the above-mentioned techniques. The efficacy of the proposed methods is also compared by an energy-based technique with proper threshold selection to accurately detect the islanding phenomena. Further, to augment the accuracy of the result, the classification is done using support vector machine (SVM) to distinguish islanding from other power quality (PQ) disturbances. The results demonstrate effective performance and feasibility of the proposed techniques for islanding detection under both noise-free and noisy environments, and also in the presence of harmonics.

Implementation of Active Anti-Islanding Methods Protection Devices for Grid Connected Photovoltaic Systems

Single-phase grid tied inverter is one among types of inverters widely used in photovoltaic generation systems due to the advantages they offer, in the absence of the grid, islanding situations occur. This paper describes model and simulation of such inverter in operation as distributed generation in electrical power system under islanding phenomena. In this configuration, it is imperative that the inverter automatically disconnects from the grid without remaining any residual voltage that can be dangerous for the plants and stakeholders. It is important to detect the islanding situation. For this purpose several techniques are used. We present in this article the implementation of the method called Slide-Mode frequency Shift (SMS) in the control of a single phase photovoltaic inverter, for which we provide a description of our SIMULINK implementations and their evaluations performed on the basis of comparison with Active Frequency Drift (AFD) method. Simulation results show that the developed algorithm detects the islanding phenomenon in the time approaching that required by the IEC and IEEE standards that secures the PV system connected to the grid.  Index Terms—PV systems, electrical grid, islanding detection methods, single phase PV inverter, distributed generation systems

Islanding Detection Method of a Photovoltaic Power Generation System Based on a CMAC Neural Network

This study proposes an islanding detection method for photovoltaic power generation systems based on a cerebellar model articulation controller (CMAC) neural network. First, islanding phenomenon test data were used as training samples to train the CMAC neural network. Then, a photovoltaic power generation system was tested with the islanding phenomena. Because the CMAC neural network possesses association and induction abilities and characteristics that activate similar input signals in approximate memory during training process, the CMAC only requires that the weight values of the excited memory addresses be adjusted, thereby reducing the training time. Furthermore, quantification of the input signals enhanced the detection tolerance of the proposed method. Finally, the simulative and experimental data verified the feasibility of adopting the proposed detection method for islanding phenomena.

안티아일랜딩 기능을 적용한 전기자동차 충전계통 연계 스마트그리드 모니터링 시스템 개발

In this paper, we present a smart grid monitoring system connected with electric vehicle charging system using anti-islanding method. Electric vehicles can be charged through remote control of smart grid monitoring system and the charging process may be more stable and more efficient by virtue of wireless communication between the Local Area Module and End Modules. It is illustrated by some experiments that electric vehicle charging process continued without any serious fault even though the islanding phenomena occurred in the grid if the presented monitoring system was applied to the smart grid system.

Power generation confirmation of induction motors and influence on islanding detection devices

AbstractPhotovoltaic generation systems must have protection devices and islanding detection devices if they are connected to utility lines of the electric power company. This is regulated in national technological requirement guidelines and the electric equipment technology standards. Islanding detection devices are installed to detect blackouts due to events such as ground faults and short circuits in utility lines. When an islanding detection device detects a power blackout, the photovoltaic generation system must be stopped immediately. It is known that islanding detection devices cannot detect islanding if induction motors are present among the loads. We investigated the influence of induction motors on islanding detection devices and found that when the frequency decreases after a utility line failure, induction motors change over to generator mode, thus compensating the active power imbalance and suppressing voltage variation. In addition, if the postfault frequency is adjusted by PLL control so as to maintain a fixed power factor, induction motors suppress this frequency change, thus extending islanding operation. It is clear from the above results that induction motors are more likely to produce islanding phenomena than static loads. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(4): 8–18, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20962

DC–AC switching converter modelings of a PV grid-connected system under islanding phenomena

Nonlinear modeling of a dc–ac full-bridge switching converter PV grid-connected system under islanding phenomena is proposed. It is a model that can be easily derived by using simple analytical techniques. A state-space averaging technique (no linearization) and voltage source inverter with current control are performed as “large-signal modeling” that is used to analyze the dynamic response of load voltage under 3 different resistive loads: 125%, 100% and 25% of inverter output and RLC when the grid system is disconnected as well as a step change of load. The nonlinear equation from the proposed modeling is handled by MATLAB/SIMULINK. The results of the proposed model are compared with experiments and PSpice simulation which shows good agreement among them. Moreover, it is found that the proposed model consumes much less computation time than PSpice and does not encounter any convergence problem.

Synchronized Injection Method of Distributed Inter-Harmonic Currents and its Application to Detection of Islanding Operation under Clustering Installation of Distributed Generators

This paper describes synchronized injection method of distributed inter-harmonic currents, and inspection of new islanding operation detection method for clustering installation as its application. If small distributed generators (DG) interconnected with low voltage system are installed under clustering, when a intersystem fault occur between high and low voltage grid, islanding phenomena will pose a problem. The following methods are conventionally considered as a measure.(1) Method by distribution system facilities(2) Application of conventional islanding detection method (indirect detection of earth fault)However, the subject of maintenance of a system occurs by (1). The subject to which detection time becomes long depending on system conditions can be considered by (2). Then, in order to solve these subjects, we developed this new method.

A CPAT Simulation Analysis on the Effect of Islanding Protection under Clustered PV Application 500 PV Systems

Since the FY2003, the demonstration site Josai-no-mori including over 500 residences with PV system has been under construction at the Ota City, Gunma prefecture in Japan. It is important to clear the safety of islanding protection. However, it is very difficult to verify the islanding phenomena including many PV systems on the actual utility grid, where the people are leading life actually. Therefore, it becomes important to develop a technique employing simulation analysis for the safety evaluation.Purpose of our study is to clear the details of dangerous islanding phenomena and the effects of various protection methods under clustered installation of over 500 PV systems within a partial area of utility grid. To solve these problems, a new analysis method has been developed, that is based on the CRIEPI's Power system Analysis Tools (CPAT) technology implemented by CRIEPI, so called “Y-method".As a noteworthy result, it has been confirmed that the new simulation method has a capability to expand to the large-scale clustered installation model including 500 PV systems on utility grid. The validity of simulation analysis has been verified by comparing with preliminary indoor tests. In addition, it has been clarified that the combination of passive and active protection methods is very effective to avoid the islanding phenomena.

Modeling anti-islanding protection devices for photovoltaic systems

Applications of grid-connected photovoltaic systems are rapidly expanding, providing a viable technology for renewable energy resources. Such systems are utility interactive and one of the major difficulties in their efficient use is related to islanding phenomena connected with a possibility of supplying surplus power back to the utility grid. In detecting and preventing such situations, anti-islanding protection devices play a paramount role. In this paper, we analyze the existing techniques in order to identify a methodology with an optimum combination of characteristics. We implement the chosen methodologies in SIMULINK. Major attention is given to the phase jump detection method (PJD), and to the slip mode frequency shift method (SMS) for which we provide a detailed description of our SIMULINK implementations and their evaluations performed on the basis of their non-detection zones. We develop an experimental iterative scheme to validate the results of computational experiments obtained with the developed models, and report the results of several computational tests.

Influence of the electrochemical potential on energy landscapes near step- and island-edges: Ag(100) and Ag(111)

The electrochemical cell offers the promise of enabling controlled alteration of the morphology and islanding phenomena on metallic surfaces. Different diffusion processes near step and island edges are known to profoundly affect the growth mode, island sizes, island shapes and step morphology. Using the surface-embedded-atom model (SEAM) modified for the electrolytic environment, we calculate the dependence of the activation energies for these diffusion processes on the electrochemical potential for the Ag(100) and Ag(111) surfaces. While all these processes show some degree of dependence on the potential, the step-edge barrier and the edge diffusion processes are the most sensitive. Step-edge barriers for Ag(111) increase (to over 1eV) with a 1.0V potential (relative to the potential of zero charge (PZC)). The variations for Ag(100) are not as large (about 0.3eV), but the excess step-edge barrier can be negative for high positive (>+0.6V) or negative (<−0.4V) potentials owing to the competing roles of hopping and exchange diffusion processes and their dependencies on the potential. Edge diffusion decreases rapidly with potential for both (100) and (111) surfaces. Significant variations are also found for diffusion around corners and kinks, which play important roles in island morphology. We assess the influence these variations have on island sizes, shapes, diffusion, and coarsening. From this discussion, we show how the electrochemical potential can be used to control the fractal or compact nature of islands, and the magnitude and scaling exponent for island diffusion and coarsening.

Influence of The Electrochemical Environment on Diffusion Processes Near Step and Island Edges: Ag(111) and Ag(100)

AbstractThe electrochemical cell provides a potentially powerful means of altering morphology and islanding phenomena on metallic surfaces. Diffusion and attachment processes on terraces and near step and island edges are known to profoundly affect island sizes, shapes and coarsening kinetics. Using the surface-embedded-atom-model (SEAM) for describing metallic surfaces in the electrolytic environment, we calculate the dependence of the activation energies for the aforementioned diffusion processes on the deposited surface charge for the Ag(111) and Ag(100) surfaces in an electrolytic environment. While all these processes show some degree of dependence on the potential, the step-edge barrier and the edge diffusion processes are the most sensitive. Step-edge barriers increase (to over 1 eV) with large positive potential (0.85 V), while edge diffusion barriers monotonically decrease with positive surface charge on Ag(100) and Ag(111). We assess the effect these diffusion barriers have on island size/shapes and coarsening dynamics and discuss the implications on electrochemical tuning of islanding phenomena.

Surface diffusion of Ge on Si(111): Experiment and simulation

Surface diffusion of Ge on Si(111) at high temperatures has been examined experimentally by second-harmonic microscopy and computationally by molecular-dynamics simulations with a Stillinger-Weber potential. Experimentally, the activation energy and preexponential factor for mass-transfer diffusion equalled 2.48\ifmmode\pm\else\textpm\fi{}0.09 eV and 6\ifmmode\times\else\texttimes\fi{}${10}^{2\ifmmode\pm\else\textpm\fi{}0.5}$ ${\mathrm{cm}}^{2}$/s, respectively. Simulational results yielded essentially the same numbers, confirming the utility of the Stillinger-Weber potential for diffusional studies. A previously developed semiempirical correlation also did fairly well. The simulations also provided estimates for the corresponding parameters for intrinsic diffusion and for the enthalpy and entropy of Ge adatom-vacancy pair formation on Si. The simulations further yielded evidence for minor contributions of atom exchange to intrinsic diffusion, as well as the complex high-temperature islanding phenomena on picosecond time scales.