Anti-islanding Protection Scheme 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

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

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.

Small Signal Stability Analysis Oriented Design of Hybrid Anti-Islanding Protection Technique Based on Active Disturbance Injection

The conventional over/under voltage, over/under frequency based anti-islanding protection scheme presents significant nondetection zone (NDZ) under critical loading conditions of distribution networks. To overcome this challenge, a unique hybrid technique has been proposed in this article for the anti-islanding protection of distributed generators (DGs). The algorithm requires the injection of an active oscillatory disturbance signal of very small magnitude through the current control loop along the direct axis of the synchronously rotating reference frame of the converter. Small signal stability analysis of the system is carried out to analyze the effect of such active signal injection having different frequencies. The anti-islanding protection algorithm first involves the superimposition of d-axis voltage. Thereafter, two novel indexes are proposed based on which the trip signal logic is developed for the protection scheme. The methodology has been found to detect an unintentional islanding scenario within 90 ms from the initiation instant. The efficacy of the proposed hybrid anti-islanding protection scheme is tested under various abnormal operating conditions by performing simulations on the CIGRE LV test system. Experimental validation of the proposed methodology has also been carried out in Controller Hardware-in-the-Loop (CHIL) platform using Typhoon HIL 602+ and Speedgoat baseline real-time target machine.

Analysis and Mitigation of the Impact of Ancillary Services on Anti-Islanding Protection of Distributed Generators

The incorporation of ancillary services on distributed generators (DGs) at utility level has imposed several challenges on the existing distribution networks. To address one of such problem, this paper discusses the impact of ancillary services, mainly the voltage ride through (VRT) capability and active power curtailment control (APCC) of DGs on their anti-islanding protection scheme (AIPS). In this study, different types of load models (viz. ZIP, induction motor (IM) and composite loads) have been considered and non-detection zone (NDZ) characteristics are obtained for a modified IEEE 1547/ UL 1741 test system for analyzing the problem. Further demonstration of this issue has been carried out by conducting time domain simulations in PSCAD/EMTDC platform on modified IEEE 1547 and CIGRE low voltage benchmark test system having composite loads at each of the load buses. Finally, an appropriate mitigation framework has been proposed by incorporating a hybrid islanding detection technique to enable simultaneous implementation of VRT, APCC and AIPS in DGs. The online implementation of the proposed framework is realized in MATLAB/Simulink platform and real-time simulations are performed in OPAL-RT (OP5600) test bed on the modified IEEE 1547/ UL 1741 test system for validating its efficacy.

An Anti-Islanding Protection for VSM Inverters in Distributed Generation

Virtual synchronous machine (VSM) technology is an attractive control method for an inverter-based distributed generation (DG) due to having the voltage, and frequency support functionality. Embedding an anti-islanding protection (AIP) scheme with a high accuracy is a requirement for DG inverters due to the safety concern of the personnel, and hazardous operation. This paper presents a novel hybrid AIP scheme for VSM inverters for integration of DG sources into the grid. The main advantage of this AIP scheme is that the proposed scheme can be embedded into the control of the DG inverters without a need of additional part in the hardware of the inverter, and any change in the controller. A detailed modeling of its implementation with the inverter control is presented, and the performance of the AIP scheme is verified by simulations, and experiments. It is shown that the AIP scheme detects the islanding condition successfully, and isolates the inverter from the grid after it experiences an islanding condition.

A new approach for islanding management in PV system using frequency modulation technique and simple adaptive load shedding algorithm

One of the main challenges in distributed generation is to keep supplying some priority loads when islanding occurs. Unfortunately, most anti-islanding protection (AIP) methods fail in islanding detection if the demand in the islanded loads matches the production in the island. Many active AIP schemes are too slow and cause power quality problems. In this paper, an islanding detection method for inverter-based photovoltaic system (PVS) is presented, operating with a simple adaptive loads shedding algorithm. This method is based on modulating the inverter output voltage at the point of common coupling. This frequency modulation consists in introducing interharmonics as side bands of the inverter voltage. After islanding detection, the adaptive loads shedding algorithm operates so as to keep powered priority loads as possible. AIP scheme and PVSs are implemented in MATLAB/Simulink environment. The effectiveness of the proposed scheme was tested and evaluated under a wide range of operating conditions. These tests determined that the proposed technique does not exhibit any non-detection zone and detects islanding within five electric cycles. No significant effect on power quality is recorded even during islanding detection time. The proposed technique was also robust and more independent of system parameters than some others.

Anti-Islanding Protection of PV-Based Microgrids Consisting of PHEVs Using SVMs

The cheap and reliable primal energy source for battery energy storage system (BESS) refueling necessitates a special attention for combining renewable energy resources with plug-in hybrid electric vehicle (PHEV) charging stations in microgrids. Rapid charging is an operation mode of PHEV for drivers which demands fast recharging of BESSs of the electric cars. This charging mode manifests as low impedance short circuit at dc side, making power transient on power grid side. This paper presents a new anti-islanding protection scheme for low-voltage-sourced converter-based microgrids by exploiting support vector machines (SVMs). The proposed anti-islanding protection method exploits powerful classification capability of SVMs. The sensor monitors seven inputs measured at the point of common coupling (PCC), namely, root-mean-square (RMS) value of voltage and current ( $RMS_{V}$ , $RMS_{I}$ ), total harmonic distortion (THD) of voltage and current ( $THD_{V}$ , $THD_{I}$ ), frequency ( $f$ ), and also active and reactive powers ( $P$ , $Q$ ). This approach is based on passive monitoring and therefore, it does not affect the power quality (PQ). In order to cover as many situations as possible, minimize false tripping and remain selective, training, and detection procedures are simply introduced. Based on the presented sampling method and input model, the proposed method is tested under different conditions such as PHEV rapid charging, additional load change and multiple distributed generations at the same PCC. Simulations based on the model and parameters of a real-life practical photovoltaic power plant are performed in MATLAB/Simulink environment, and several tests are executed based on different scenarios and compared with previously reported techniques, this analysis proved the effectiveness, authenticity, selectivity, accuracy, and precision of the proposed method with allowable impact on PQ according to UL1741 standard, and its superiority over other methods.

Islanding detection of distributed generation by using multi-gene genetic programming based classifier

This paper proposed a new method for detecting islanding of distributed generation (DG), using Multi-gene Genetic Programming (MGP). Islanding has been a serious concern among power distribution utilities and distributed generation owners, because it poses risks to the safety of utilities’ workers and consumers, and can cause damage to power distribution systems’ equipment. Therefore, a DG must be disconnected as soon as an islanding is detected. In addition, an islanding detection method must have high degree of dependability to correctly discriminate islanding from other events, such as load switching, in order to avoid unnecessary disconnection of the distributed generator. In this context, the novelty of the proposed method is that the MGP is capable of obtaining a set of mathematical and logic functions employed to detect and classify islanding correctly. This is a new approach among the computational intelligent methods proposed for DG islanding detection. The main idea was to use local voltage measurements as input of the method, eliminating the need of complex and expensive communication infrastructure. The method has been trained with several islanding and non-islanding cases, by using a power distribution system comprising five concentrated loads, a synchronous distributed generator and a wind power plant. The results showed that the proposed method was successful in differentiating the islanding events from other disturbances, revealing its great potential to be applied in anti-islanding protection schemes for distributed generation.

Islanding detection of synchronous distributed generators using data mining complex correlations

This study proposes a novel method based on data mining for islanding detection of synchronous distributed generators. The method uses a new technique called data mining of code repositories (DAMICORE), which is a powerful data mining tool for detecting patterns and similarities in various kinds of datasets. In addition, a trip logic was developed in this proposal in order to detect islanding and disconnect the distributed generator. One of the most relevant features of the proposed method is its capability to generalise, which reduces the need of big datasets for training purposes. This approach has been tested with islanding, load switching and fault simulations, presenting promising results concerning performance, as well as detection time. General results showed a better performance of the method if compared to traditional anti-islanding protection schemes, such as frequency-based relays.

Comprehensive investigation of the voltage relay for anti-islanding protection of synchronous distributed generation

Summary Interconnection standards prevent islanding operation of distributed generations (DGs) to keep the safety and avoid the equipment failure. To meet this requirement for synchronous DGs (SDGs), the frequency-based relays are commonly used in the active distribution networks. This paper shows that in some conditions, a voltage relay has better islanding detection performance than a frequency relay regarding the SDG operating point, power factor of loads, and network characteristics. In this paper, a method is proposed for adjusting and evaluating a voltage relay based on application region and power imbalance application region to satisfy the islanding detection and safe and abnormal voltage variation criteria and to eliminate the false operation for the non-islanding disturbances including load shedding, load restoration, and 3-phase short-circuit fault, as far as possible. The relay false operation is studied for a combination of the control mode of SDG excitation system and the load type that leads to the highest possibility of relay false operation for the non-islanding disturbances. A number of dynamic simulation case studies are conducted to investigate the characteristics and capabilities of the proposed SDG anti-islanding protection scheme in both single- and multi-DG systems.

An Anti-Islanding Protection Method Based on Reactive Power Injection and ROCOF

All distributed-generation units need to be equipped with an anti-islanding protection (AIP) scheme in order to avoid unintentional islanding. Unfortunately, most AIP methods fail to detect islanding if the demand in the islanded circuit matches the production in the island. Another concern is that many active AIP schemes cause power-quality problems. This paper proposes an AIP method which is based on the combination of a reactive power versus frequency droop and rate of change of frequency (ROCOF). The method is designed so that the injection of reactive power is of minor scale during normal operating conditions. Yet, the method can rapidly detect islanding which is verified by PSCAD/EMTDC simulations.

Nondetection Index of Anti-Islanding Passive Protection of Synchronous Distributed Generators

Synchronous distributed generators are prone to operate islanded after contingencies, which is usually not allowed due to safety and power-quality issues. Thus, there are several anti-islanding techniques; however, most of them present technical limitations so that they are likely to fail in certain situations. Therefore, it is important to quantify and determine whether the scheme under study is adequate or not. In this context, this paper proposes an index to evaluate the effectiveness of anti-islanding frequency-based relays commonly used to protect synchronous distributed generators. The method is based on the calculation of a numerical index that indicates the time period that the system is unprotected against islanding considering the global period of analysis. Although this index can precisely be calculated based on several electromagnetic transient simulations, a practical method is also proposed to calculate it directly from simple analytical formulas or lookup tables. The results have shown that the proposed approach can assist distribution engineers to assess and set anti-islanding protection schemes.

Power imbalance application region method for distributed synchronous generator anti-islanding protection design and evaluation

This paper presents a novel graphical approach to adjust and evaluate frequency-based relays employed in anti-islanding protection schemes of distributed synchronous generators, in order to meet the anti-islanding and abnormal frequency variation requirements, simultaneously. The proposed method defines a region in the power mismatch space, inside which the relay non-detection zone should be located, if the above-mentioned requirements must be met. Such region is called power imbalance application region. Results show that this method can help protection engineers to adjust frequency-based relays to improve the anti-islanding capability and to minimize false operation occurrences, keeping the abnormal frequency variation utility requirements satisfied. Moreover, the proposed method can be employed to coordinate different types of frequency-based relays, aiming at improving overall performance of the distributed generator frequency protection scheme.

RETRACTED: UK scenario of islanded operation of active distribution networks with renewable distributed generators

This paper reports on the current UK scenario of islanded operation of active distribution networks with renewable distributed generators (RDGs). Different surveys indicate that the present scenario does not economically justify islanding operation of active distribution networks with RDGs. Anti-islanding protection schemes currently enforce the renewable distributed generators (RDGs) to disconnect immediately and stop generation for grid faults through loss of grid (LOG) protection system. This greatly reduces the benefits of RDG deployment. With rising RDG penetration, much benefit would be lost if the RDGs are not allowed to island only due to conventional operational requirement of utilities. For preventing disconnection of RDGs during LOG, several islanding operation, control and protection schemes are being developed. Technical studies clearly indicate the need to review parts of the ESQCR (Electricity Safety, Quality and Continuity Regulations) for successful islanded operations. Commercial viability of islanding operation must be assessed in relation to enhancement of power quality, system reliability and supply of potential ancillary services through network support. Demonstration projects under Registered Power Zone and Technical Architecture Projects should be initiated to investigate the usefulness of DG islanding. However these efforts should be compounded with a realistic judgement of the associated technical and economic issues for the development of future power networks.

Islanding protection of active distribution networks with renewable distributed generators: A comprehensive survey

Anti-islanding protection schemes currently enforce the renewable distributed generators (RDGs) to disconnect immediately and stop generation for grid faults through loss of grid (LOG) protection system. This greatly reduces the benefits of RDG deployment. For preventing disconnection of RDGs during LOG, several islanding operation, control and protection schemes are being developed. Their main objectives are to detect LOG and disconnect the RDGs from the utility. This allows the RDGs to operate as power islands suitable for maintaining uninterruptible power supply to critical loads. A major challenge for the islanding operation and control schemes is the protection coordination of distribution systems with bi-directional flows of fault current. This is unlike the conventional overcurrent protection for radial systems with unidirectional flow of fault current. This paper presents a comprehensive survey of various islanding protection schemes that are being developed, tested and validated through extensive research activities across the globe. The present trends of research in islanding operation of RDGs are also detailed in this paper.

An Investigation on the Nondetection Zones of Synchronous Distributed Generation Anti-Islanding Protection

Anti-islanding protection is an important technical requirement when interconnecting distributed generators. Unfortunately, most anti-islanding protection schemes cannot detect islanding situations under certain system operating conditions - there are nondetection zones within which anti-islanding protection schemes are ineffective. This paper investigates these nondetection zones associated with the common anti-islanding protection schemes of synchronous distributed generators: frequency and voltage-based relays. Moreover, the characteristics of the nondetection zones and the key factors that influence them are analyzed. The results are useful for utility companies and distributed generators owners to design and to evaluate the effectiveness of anti-islanding protection schemes proposed for various distributed generation interconnection projects.

A Power Line Signaling Based Scheme for Anti-Islanding Protection of Distributed Generators—Part II: Field Test Results

Anti-islanding protection of distributed generators (DG) is a significant technical barrier to the emerging DG industry. In response to this challenge, a power line signaling based anti-islanding protection scheme has been proposed in a companion paper. The scheme broadcasts a signal from a substation to the DG sites using the distribution feeders as signal paths. A DG is considered as islanded from the upstream system if the signal is not detected at the DG site. This paper presents extensive field test results and experiences obtained for the proposed scheme. The results confirm that the proposed scheme is a very promising and economical method to satisfy anti-islanding protection requirements for synchronous DG interconnections.