Anti-islanding Protection Research Articles

A Novel Two-Stage Hybrid Anti-Islanding Protection Scheme and Nondetection Zones Analysis of Inverter-Based Generations

A Novel Two-Stage Hybrid Anti-Islanding Protection Scheme and Nondetection Zones Analysis of Inverter-Based Generations

A heuristic-based method for setting synchronous distributed generators excitation system parameters to improve islanding detection

Passive anti-islanding protections rely on measurements of voltage, frequency, and rate of change of frequency at the point of common coupling of the distributed generators, and their performance is impacted by the dynamic behavior of distributed generators operating under specific control modes. In this context, this paper proposes a novel heuristic-based method for setting the excitation system parameters of synchronous distributed generators using the differential evolution algorithm to enhance the performance of anti-islanding protection. The results demonstrate that the heuristic-based method achieves improved islanding detection performance compared to traditional values used to specify excitation system parameters. Furthermore, the optimized excitation system parameters do not adversely affect the transient response of the generator during fault events.

Proactive control to mitigate voltage violations after DER disconnection

During the last few decades, extensive research has been conducted to mitigate potential voltage-related problems that high penetration of Distributed Energy Resources (DERs) may cause. One of these problems is the voltage variation caused by the disconnection of the DERs due to their anti-islanding protection action after a temporary fault. This issue has not been deeply studied so far and it may pose severe voltage variations to distribution systems’ consumers. In this context, this paper proposes a new formulation aiming at the preventive voltage regulation strategy for step voltage regulators considering the impacts triggered by a sudden disconnection of DERs. The voltage control is accomplished by a specialized Particle Swarm Optimization that selects control actions predicting the possibility of the DERs being disconnected. Results show that voltage violations were minimized after the disconnection of DERs, keeping the nodal voltages within statutory limits.

Probabilistic method for risk analysis of unintentional islanding of distributed generators

Unintentional islanding can be a harmful event, requiring the fast actuation of the anti-islanding protection to disconnect the distributed generators. Although passive techniques are mostly used, they have non-detection zones and fail to detect islanding under specific conditions. Therefore, knowing in advance such operative conditions and the risks associated with the islanding occurrence can be a strategic information to support grid operators in the decision-making process regarding the effectiveness of distributed generators interconnection protection. In this context, this paper proposes a probabilistic method to assess the risk of energized island formation by combining the probability of breaker (or recloser) opening with the probability of anti-islanding protection failure. The method employs probabilistic short circuit associated with overcurrent protection actuation by using Monte Carlo simulation and time-domain analysis to obtain the cases of unintentional islanding and to calculate the risk of distributed generator islanded operation. The results drove more realistic and less conservative conclusions than previous literature. Additionally, it is shown that faults as the cause of breaker opening do play a relevant role in the performance of the anti-islanding protection.

Event-Triggered Hybrid Anti-Islanding Protection Scheme Based on Q-Axis Disturbance Injection

Event-Triggered Hybrid Anti-Islanding Protection Scheme Based on <i>Q</i>-Axis Disturbance Injection

Integrated Passive Anti-Islanding Protection in Micro Grid

In last two decades due to major interest amongst power system engineers and policy makers penetration of different distributed energy resources (DREs) into power distribution network are significantly increased. Integration of DREs with conventional power grid is a complex issue and will impose some challenges against power engineers. The major challenge is protection of micro grid, which is based on how your protection strategies distinguish islanding and non islanding conditions correctly and timely. Methods used for have strengths and limitations in the areas like speed, accuracy, power quality and Non detection islanding zone. The prime motive of this research is to presents an efficient new integrated anti-islanding protection strategy using passive parameters. The proposed algorithm having a novel islanding detection technique, which discriminate the islanding events from the non islanding events of similar signature accurately with minimum non detection zone and minimum impact on power quality. The proposed strategy is the combination of different conventional and latest passive relays based on single and multiple parameters. Integration of different relays made in such a strategic way that it combines the strengths and benefits of each method and minimizes their limitations. The presented algorithm tested under MATLAB/SIMULINK environment in different network conditions. Finally, the efficiency of the algorithm has checked by testing it on standard microgrid structure. The results received from simulation confirmed that algorithm is detecting islanding conditions reliably and efficiently, followed by generation of trip/block signal correctly.

Voltage Frequency Differential Protection Algorithm

Advancements in new technologies, a reduction in CO2 emissions, and the rising demand for energy are causing a growth in the share of renewable energy sources. In distribution networks, an increasing number of distributed generators (DGs) makes the utility grid’s protection complex and demanding. Vector surge and rate-of-change-of-frequency are the established anti-islanding protection methods, recognizing that the standard paradigm for protection, involving distributed generation, cannot be set only once but has to be continuously updated following the requirements and changes in the system. One of the requirements is active participation in the preservation of system frequency and voltage, which can be interrupted if the DG trips and disconnects from the utility grid. Anti-islanding protection and spurious tripping can be avoided by implementing new algorithms and techniques. This paper presents a novel protection scheme based on a voltage frequency differential. The proposed algorithm employs remote and local frequency measurements in such a manner that, for the occurrence of a frequency difference, it is assumed that the DG is in an islanding state. In this article, we demonstrate the feasibility of the algorithm through numerical analysis of grid events and laboratory testing emulating real grid-measured values. The test results show that the algorithm is resilient to false tripping for non-islanding events and more reliable than conventional methods in islanding detection. The algorithm can be set to low-frequency differential values, drastically reducing the non-detection zone in any DG type, regardless of its size and voltage level at the point of common coupling. Unlike standard anti-islanding methods, the algorithm supports the ability of the DG to fault-ride through demand.

Measurement of impedance angle for anti-islanding protection in multi-source distribution network

With the increase of the proportion of distributed generators (DGs) access in the distribution network, it transforms from a traditional radial network to a multi-terminal active network, which brings many challenges to relay protection. If part of the distribution network is disconnected from all upstream networks, it can create unplanned islands that can compromise personal safety, power quality, and out-of-phase reclosing. As a result, it is essential to equip DGs with anti-islanding protection. Currently, anti-islanding protection based on impedance measurement is of great interest because it has the lowest risk of rejection and misoperation. However, in multi-source distribution networks, signal interference can lead to protection failure. In light of this, we proposed an impedance angle measurement anti-islanding protection based on voltage synchronous injection, where each DG uses the bus voltage as a reference to achieve synchronous injection of the islanding detection signal. The measured impedance angle was then used to identify the state of islanding operation. Combining the analyses of line impedance, injected signal frequency and other relevant factors, an impedance angle based islanding identification criterion is proposed. Furthermore, the realization method of signal injection and impedance angle detection in combination with the DG control strategy was presented. Finally, real-time digital simulation (RTDS) experiments show that the proposed method can accurately identify islands under zero power mismatch conditions and independent of grid disturbances.

Bayesian Entropy Methodology: A Novel Approach to Setting Anti-Islanding Protections with Enhanced Stability and Sensibility

The risk of unintentional islanding creation in distributed energy systems poses a significant security concern since unintentional islanding formation could lead to a supply of energy outside of the optimal quality limits. This constitutes a risk for users, maintenance personnel, infrastructure, and devices. To mitigate this problem, anti-islanding protections are widely used to prevent the distributed generator from feeding a portion of the radial distribution grid when a protection device trips upstream. However, the effectiveness of these protections heavily relies on properly tuning protection setting thresholds (such as time delay and pickup). This work proposes a novel approach that utilizes entropy as a model and metric of the uncertainty associated with a particular protection setting. By minimizing entropy, the proposed method aims to improve stability and sensitivity, consequently improving the overall performance of anti-islanding protection. Simulation results demonstrate that the Bayesian entropy methodology (BEM) approach achieves enhanced stability in various scenarios, including frequency transients, and demonstrates a notable reduction in the size of the dataset and computational burden, ranging between 91% and 98%, when compared to related works, with an improvement of the uncertainty achieved. The findings of this study contribute to the development of more robust and reliable anti-islanding protections.

The effect of inrush transients on PV inverter’s grid impedance measurement based on inter-harmonic injection

This paper addresses a cause for false tripping of photovoltaic inverters with anti-islanding protection based on impedance measurement with inter-harmonic injection. Earlier discussions about tripping problems happening when several devices are doing the measurement at the same time are supplemented with a problem caused by inrush transients of nearby devices. A series of experiments was conducted in the Power Quality laboratory of the TU/e, on a PV inverter which complies with the DIN VDE 0126 standard. Impedance measurement was done in parallel with the inverter and measurement results are presented. A criterion for false tripping caused by transients is explored. Also, influences of network impedance and grid harmonic pollution on false tripping were analyzed. In the end, some signal processing techniques are proposed to avoid this problem.

Analysis of Remote Islanding Detection Methods for Distributed Resources

Penetration of distributed generation in the power grid is increasing. This situation leads to new possibilities but also new issues, such as anti-islanding protection. During a loss-of-mains or islanding situation, distributed generation (DG) units remain feeding a part of the electrical network without connection to the main power system. Currently, DG units have to be disconnected from the grid during islanding as soon as possible, due to potential risks for repair crews and components, poor power quality in the island and reclosing problems. A fast and reliable islanding detection method could avoid mentioned issues. Among the many existing methods, remote schemes could meet these requirements. Hence, this paper presents the operating principles of remote islanding detection methods, as well as the current state of development of communication-based remote islanding detection methods to be applied in distributed power generation systems.

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.

An Anti-Islanding Protection Method Based on Voltage-Synchronous Impedance Angle Measurements

Grid-tied distributed generators (DGs) need to be equipped with anti-islanding protection to avoid the impact of unplanned islanding, which would affect system stability, auto-reclosing, and personal safety. Among the active anti-islanding protections, impedance measurements based on signal injection have the advantages of a low non-detection zone (NDZ) and are less prone to maloperation during grid disturbances; however, there are problems with signal interference in multi-DG systems. Hence, the impedance angle measurement method with signals injected synchronously is proposed. In this method, each DG injects phase-coherent signals to detect islanding using zero-cross points of the voltage (ZCPV) to avoid the protection failures caused by signal interference. An islanding identification criterion based on the measured impedance angle is proposed by analyzing the impedance characteristics of grid connection and islanding, which avoids the influence of variation of the DG operation state on islanding detection. Finally, we present a signal injection strategy and performance analysis in combination with an existing DG control platform, avoiding additional hardware investment. RTDS-based simulation verification shows that the proposed method can 100% avoid DG maloperation due to voltage and frequency disturbances during grid-connected operation and exit operation within 2 s when islanding occurs.

Design of Function of Anti-islanding in Novel Power Distribution System with Distributed New Energy Access

With the proposal of “Double-Carbon” goal and the acceleration of energy transformation, a large number of distributed new energy sources such as photovoltaics and wind power, are connected to the power distribution system, the power distribution system has developed into a novel distribution system with the optimization and coordination of energy as its core, thus put forward higher requirements for the safety protection of distribution network. However, when the line of distribution network is repaired or faulty, the power distribution system is very easy to cause islanding effect. Measures of anti-islanding are still implemented based on the grid-connected inverter on the user’s side, and there may be dead zones for anti-islanding protection or other abnormal situations. From the perspective of a novel power distribution system, this paper proposes the method of anti-islanding in novel distribution system with distributed new energy access. The identification of islanding criterion signal, the determination of islanding operation’s area, the generation and execution of islanding processing strategy, the evaluation of islanding processing result and the display of anti-islanding function are elaborated in detail. By analyzing the scenarios of actual application of the anti-islanding processing method, the proposed method can accurately sense the state of islanding of the distribution network and quickly isolate the operating area of islanding through remote control, and the novel power distribution system with distributed new energy access can be prevented from running in islanding, which greatly improves the efficiency of anti-islanding processing for dispatchers, so as to ensure the safe, stable and reliable operation of the distribution network.

Passive anti-Islanding protection for Three-Phase Grid-Connected photovoltaic power systems

This paper presents the performances of a new passive anti-islanding protection with minimal switching losses for three-phase grid-connected photovoltaic power systems. The novelty of the proposed strategy consists of five conventional passive relays, which are as follows: over/under current, over/under voltage, over/under frequency, rate of change of frequency, and dc-link voltage-based anti-islanding methods. Integrating these methods in a synergistic way reduces the limitations of each method, while combining the strengths and benefits of each method in islanding detection. As such, the dc-link voltage-based method consists in supervising the dc-link voltage in voltage source converters to reduce the voltage stress and increase performance. The performance in islanding prevention is determined by the detection time of islanding operation mode. The proposed anti-islanding protection was simulated under complete disconnection of the photovoltaic inverter from the electrical power system, as well as under grid faults as required by new grid codes.

Impact of Cascade Disconnection of Distributed Energy Resources on Bulk Power System Stability: Modeling and Mitigation Requirements

This work presents a new approach to establishing the minimum requirements for anti-islanding protection of distributed energy resources (DERs) with focus on bulk power system stability. The proposed approach aims to avoid cascade disconnection of DERs during major disturbances in the transmission network and to compromise as little as possible the detection of real islanding situations. The proposed approach concentrates on the rate-of-change of frequency (RoCoF) protection function and it is based on the assessment of dynamic security regions with the incorporation of a new and straightforward approach to represent the disconnection of DERs when analyzing the bulk power system stability. Initially, the impact of disconnection of DERs on the Brazilian Interconnected Power System (BIPS) stability is analyzed, highlighting the importance of modeling such disconnection in electromechanical stability studies, even considering low penetration levels of DERs. Then, the proposed approach is applied to the BIPS, evidencing its benefits when specifying the minimum requirements of anti-islanding protection, without overestimating them.

SVM-based anti-islanding protection for DER near a modern industrial premise

SVM-based anti-islanding protection for DER near a modern industrial premise

An anti-islanding protection based on RoCoF compliant with ENTSO-E and IEC 62116

In case of unintentional islanding, distributed generation units must be able to detect it and disconnect from the grid in less than 2 seconds. In this work, a Rate of Change of Frequency (RoCoF) method has been developed for islanding detection. Since these algorithms are conditioned by the requirements of grid codes, ENTSO-E network code and IEC 62116 have been taken into account. The RoCoF anti-islanding algorithm has been developed in MATLAB-Simulink and implemented through rapid prototyping techniques in an FPGA ALTERA Cyclone V. To check the proposed protection algorithm, simulation tests have been carried out. Finally, the RoCoF anti-islanding protection has been validated using FPGA in the loop and experimentally in a real 20- kW inverter.

A Hybrid Anti-Islanding Protection Scheme for VSM Based DG Inverter

A Hybrid Anti-Islanding Protection Scheme for VSM Based DG Inverter

Implementation and Critical Analysis of the Active Phase Jump with Positive Feedback Anti-Islanding Algorithm

The protection against the unintentional islanding of Grid-Tied inverters is an important electrical security issue addressed by the main Standards. This concern is justified in face of the fact that unintentional islanding can lead to abrupt variations of voltage and frequency, electrical damages, professional accidents, power quality degradation, and out-of-phase reclosure. In response to the islanding concern, the literature has proposed several Anti-Islanding Protection (AIP) schemes that can be divided in passive and active methods. Many of the active AIP is based on the insertion of some disturbance in the inverter current in order to deviate the frequency out of the allowed thresholds, tripping the inverter internal disconnection system. Thus, the main objective of this paper is to analyze the performance of the Active Phase Jump with Positive Feedback (APJPF) algorithm compared to other well-known frequency drift-based solutions. More than that, this work covers the Non-Detection Zone (NDZ) problem, analyzing its main mapping methodologies and the normative requirements, exposing the minimum normative recommendations a given AIP must reach to be considered functional. The last contributions of this paper are the proposal of a parametrization criterion for the Active Frequency Drift with Pulsating Chopping Factor (AFDPCF) and for the APJPF.