Frequency Relay Research Articles

Implementation and Analysis of an Efficient Soft-Switching Battery Wireless Charger with Re-Configurable Rectifier

To significantly reduce switching loss of the high frequency inverter in battery wireless charger (BWC), improve the soft-switching stability and system reliability, a novel soft-switching BWC with low loss auxiliary network and re-configurable rectifier is presented. The presented soft-switching BWC can implement the smooth switching between constant current mode (CCM) and constant voltage mode (CVM) without frequency switching and relays, which is beneficial to enhancing the system stability. With the help of a novel low energy consumption auxiliary circuit, the power switch tubes in the H-bridge inverter can implement zero-voltage soft switch-ON and zero-current soft switch-OFF in the full range, completely eliminating switching loss of the inverter. The proposed scheme can enhance the system efficiency while refraining from the soft-switching range limitation and soft-switching failure caused by the system parameter perturbation. Finally, a 1-kW soft-switching BWC principle prototype is developed to validate the effectiveness and correctness of the proposed scheme.

Fast hybrid islanding detection for DGs with inverters using maximum likelihood-based ROCOF and SFS

The present study introduces an unconventional and fast hybrid strategy for islanding detection in Distributed Generators (DGs) based on inverters. The active method utilized in this work is Sandia Frequency Shift (SFS), while the passive method is the Rate Of Change Of Frequency (ROCOF) Relay. The key contribution of this paper is the use of Maximum Likelihood to estimate the ROCOF as opposed to the conventional Phase-Locked-Loop (PLL) method. The objective of this paper is to improve the responsiveness of detection across various conditions by providing fast detection without compromising accuracy. Several simulation investigations, adhering to the anti-islanding test standards of IEEE 1547 and UL1741, have been carried out on a system integrated with the suggested hybrid method. These studies aim to showcase the high sensitivity and specificity of the proposed technique for detecting islanding. In addition, pertinent comparisons are made between the proposed technique and the PLL-based method. The simulation results illustrate that the proposed control system effectively complies with the DG islanding protection requirements. In Furthermore, compared to the PLL, the proposed technique mitigates the common drawbacks associated with other islanding detection techniques by reducing the Non-Detection Zone, enhancing the power quality of the system, and, most significantly, producing fast detection under different conditions. The proposed approach exhibits a response time nearly three times faster than the PLL method, while in less demanding conditions, it provides an instantaneous response.

The Significance of the Digital Frequency Relays in Grid Synchronization Maintenance

Modeling tools play a crucial role in both educational and industrial settings, enabling engineers to simulate power systems under various operating conditions, including normal and faulty scenarios. This research focuses on the design of a relay system capable of addressing both over and under frequency conditions. Digital relays exhibit distinct advantages over traditional electromechanical relays, notably in terms of accuracy and response speed. The significance of frequency control cannot be overstated, as significant fluctuations can potentially lead to complete power system blackouts. Historical incidents have demonstrated the severe consequences of frequency instability, often stemming from supply-demand imbalances and unforeseen contingencies. With the rise of distributed generation and the inherent challenges of islanding in modern power systems, the attention of both industrialists and researchers has once again turned to frequency relaying solutions. This study aims to evaluate the performance of the proposed digital frequency relay under diverse system dynamics using simulation tools such as MATLAB/Simulink and microcontroller-based implementations. By conducting rigorous testing and analysis, this research endeavors to contribute to the enhancement of grid stability and the prevention of power system disruptions caused by frequency deviations.

Protection system planning in distribution networks with microgrids using a bi-level multi-objective and multi-criteria optimization technique

Microgrids are able to improve several features of power systems, such as energy efficiencies, operating costs and environmental impacts. Nevertheless, microgrids’ protection must work congruently with power distribution protection to safely take all advantages. This research contributes to enable their protection by proposing a bi-level method to simultaneously solve the allocation and coordination problems, where the proposed scheme also includes local protections of distributed energy resources. The uncertainties associated with generation and loads are categorized by the k-means method, as well. The non-dominated sorting genetic algorithm II is employed in the upper-level task to solve the protection and control devices allocation problem with two opposing objectives. In the lower-level task, a genetic algorithm ensures their coordination. Protection devices include reclosers and fuses from the network, and directional relays for the point of common coupling of microgrids, while control devices consist of remote-controlled switches. In contrast to related works, local devices installed at the point of coupling of distributed generation units are considered as well, such as voltage-restrained overcurrent relays and frequency relays. The optimal solution for the decision-maker is achieved by utilizing the compromise programming technique. Results show the importance of solving the allocation and coordination problems simultaneously, achieving up to $25,000 cost savings compared to cases that solve these problems separately. The integrated strategy allows the network operator to select the optimum solution for the protective system and avoid corrective actions afterward. The results also show the viability of the islanding operation depending on the decision maker's criteria.

Comparative Analysis of Anti-Islanding Prevention Technique in Grid Connected PV System

Abstract: This paper presents a novel islanding prevention scheme of Grid-Connected PV Systems in Matlab/ Simulink based on monitoring the dc-link voltage of the PV inverter. A 100kW PV System equipped with islanding protection like frequency relays, a ROCOF relay, and respectively the proposed dc-link voltage relay are simulated under the conditions of islanding and the detection time for all these AI techniques are compared.

A logistic regression approach for improved safety of the under-frequency load shedding scheme owing to feeder machine inertia

Under Frequency Load Shedding (UFLS) is the last resource to maintain the power system frequency after contingences. Load shedding can be performed by conventional, adaptive, computational or wide area monitoring techniques. The most common is a conventional UFLS. Load shedding is accomplished when predetermined frequency thresholds are reached. Although the conventional methods are simple, easily implemented and dependable, they may operate improperly. In the Brazilian electric power system, several actions of the UFLS scheme were found to be improper owing to the dynamics of induction motors and distribution generation during the main source outage of distribution feeders. In this way, when the main source is out of service, machine inertia maintains the frequency for some electric cycles, leading the frequency relay to undue tripping. In this paper, the negative sequence voltage and the rate of change of frequency are handled by a logistic regression method to identify the events of improper action. The proposed method was evaluated through the modified IEEE 9-bus test system, and several cases have been tested. The proposed method reached a level of performance higher than 99% of correct operation, and it needs a small training set.

Effect on Transient Stability and Analyses Resulting from a Cyber-Attack on Frequency Relay Device

Effect on Transient Stability and Analyses Resulting from a Cyber-Attack on Frequency Relay Device

Xiroi II, an Evolved ASV Platform for Marine Multirobot Operations

In this paper, we present the design, development and a practical use of an Autonomous Surface Vehicle (ASV) as a modular and flexible platform for a large variety of marine tasks including the coordination strategies with other marine robots. This work tackles the integration of an open-source Robot-Operating-System (ROS)-based control architecture that provides the ASV with a wide variety of navigation behaviors. These new ASV capabilities can be used to acquire useful data from the environment to survey, map, and characterize marine habitats. In addition, the ASV is used as a radio frequency relay point between an Autonomous Underwater Vehicle (AUV) and the ground station as well as to enhance the Acoustic Communication Link (ACL) with the AUV. In order to improve the quality of the ACL, a new Marine Multirobot System (MMRS) coordination strategy has been developed that aims to keep both vehicles close to each other. The entire system has been successfully designed, implemented, and tested in real marine environment robotic tasks. The experimental tests show satisfactory results both in ROS-based navigation architecture and the MMRS coordination strategy resulting in a significant improvement of the quality of the ACL.

Distributed Generation Power Systems in Wastewater Management

The article concerns the energy security of a wastewater treatment process caused by unforeseen situations related to the risk of electrical power outages. In this case, renewable energy sources based on distributed generation power systems can solve this problem in each wastewater treatment plant. The article highlights e related challenges and proposes the direction of solutions in this regard based on Czech conditions. The first part of the paper deals with the consequences of long-term outage of wastewater treatment plants on the population and the environment. There are several solutions presented for blackout conditions, and model calculations are made based on data from a Czech wastewater treatment plant. Diesel engine-generators, biogas as a cogeneration source of heat and electricity, solar panels with storage systems and combined biogas and solar systems were considered as approaches to provide energy autonomy during a blackout in a wastewater treatment plant. Special attention was paid to a combination of CHP units with solar panels and batteries. The results were evaluated for three different locations for this combination. It was concluded that biogas combustion in the CHP unit was the most profitable option, allowing the production of electricity independently of the grid for its own consumption and possibly for other operations. The last part of the paper deals with the transition to island operation, which must occur during a blackout. This transition is more difficult for both solar panels and cogeneration units if they were to supply electricity to the grid before a blackout. The transition to energy island operation could be ensured by frequency relay and processor devices to control the circuit breaker. Then, to maintain island operation, it would be necessary to have an automatic load shedding/application system.

Adaptive Underfrequency Load Shedding And Voltage Stability In The Power System

Abstract Underfrequency load shedding is a common technique for maintaining the stability of the power system by removing the overload in a certain part of the system after a disturbance. The purpose of underfrequency load shedding is to balance output and load when a particular event causes a significant frequency drop in the power system. In conventional underfrequency load shedding schemes, the frequency thresholds of frequency relays are constant, this way it is difficult and sometimes impossible to control the frequency in various disturbances in the system. In this paper, an adaptive underfrequency load shedding (AUFLS) algorithm that is independent of communication between relays is presented. The relays are tuned to reduce loads taking into account local parameters such as voltage and frequency to prevent the occurrence of a cascade failure that can ultimately lead to the breakdown of the entire power system. In this paper, the rate of change of frequency (ROCOF) is obtained by applying the Hilbert-Huang transformation. Numerical simulations conducted on the New England 39 bus test system in the DIgSILENT PowerFactory and MATLAB software packages confirm the effectiveness of the proposed approach.

Optimal Coordination of Protection Devices in Distribution Networks With Distributed Energy Resources and Microgrids

Microgrids are promising to enhance power distribution systems’ efficiency, quality, sustainability, and reliability. However, microgrids operation can impose several challenges to traditional protection schemes, like changes in the power flow direction and an increase in short-circuit currents. Microgrids can include several distributed generation technologies with different behaviours during short-circuit conditions, requiring additional protection schemes and devices. In this way, the optimized coordination of reclosers and fuses in distribution networks with directional overcurrent relays, which operate as interconnection devices, might overcome many imposed protection challenges. Regarding to different generation technologies, voltage-restrained overcurrent relays and frequency relays are presented as local microgrid protection for rotative and inverter-based distributed generators, respectively. The optimized coordination of these protection devices maximizes microgrid benefits and minimizes operation drawbacks by reducing interruptions impacts and energy not supplied to consumers. This work proposes, thus, a mathematical model for the optimal coordination of protection devices in distribution networks with distributed energy resources operating in grid-connected and islanded modes. The minimization technique of operating times using an elitist genetic algorithm with variable crossover and mutation processes is proposed, as well. The results show adequate coordination using passive and low-cost protection devices.

Enhancement the Frequency Stability and Protection of Interconnected Microgrid Systems Using Advanced Hybrid Fractional Order Controller

Substituting conventional energy sources with new renewable sources is crucial issue nowadays in energy generation systems to face climate changes and increased load demands. Due to the increased penetration levels of renewable sources in power systems, the benefits of the high-inertia of conventional sources are being insufficient. The resulting low-inertia power systems introduce several stability, reliability, and coordination problems for power system operation and control. Therefore, this paper tackles the coordination assessment and enhancement between digital frequency relays using a new fractional order load frequency controller equipped with superconducting magnetic energy storage (SMES) virtual inertia system. The improved coordination method is established using optimized fractional order controller based on slime mould optimization algorithm (SMA). The proposed SMA-based design method benefits the adaptive weights of SMA algorithm. The proposed design is generalized to be applied on single area and multi-area interconnected power systems as well. Compared to existing literature, this paper presents an advanced fractional order controller with coordinated operation with existing protection relays. The obtained results show the coordination shortcomings of renewable energy based microgrids with traditional control systems. However, improved design and coordination are obtained using the proposed SMA-optimized fractional order controllers. The superiority and feasibility of the proposed analysis and methods are verified on different case studies using single and multiple interconnected areas.

Design and Development of Multifunction Frequency Relay on FPGA

Design and Development of Multifunction Frequency Relay on FPGA

Application of Battery Energy Storage Systems for Relief of Generation Curtailment in Terms of Transient Stability

Maintaining transient stability is crucial in power system operation. Transient stability is mainly affected by the generation amount of the study region, as well as the transmission topology. Several countermeasures can be taken for transient stability, but the usually used control means are generating unit tripping and generation curtailment. In terms of economic operation, one can say that the solution of generating unit tripping is more beneficial. To maintain the transient stability of the east coast region in the Korean power system, applying generation curtailment in the normal state is further needed, because the required tripping amount is too large for the case of only taking generator tripping, and this might cause a critical decrease in system frequency, possibly resulting in operation of the first stage of under frequency relay (UFR). This paper presents the application of battery energy storage systems (BESSs) to relieve the generation curtailment, using the characteristic of fast response of BESS. Assuming that BESSs are installed in the candidate location in the study region, the adequate BESS action of absorbing the kinetic energy from those critical generators after disturbances can improve transient stability, and it can decrease the amount of generation curtailment. This paper includes the results of simulation studies to show the effectiveness of the BESS control for the relief of generation curtailment.

An underfrequency load shedding scheme for high dependability and security tolerant to induction motors dynamics✰

The load shedding scheme is a last resort to prevent power system collapse when the available generation is less than the load demand. The traditional load shedding schemes monitors the frequency and voltage by underfrequency and undervoltage relays and provides load cutoff until the frequency returns to a stable point of operation. The reduction of rotating inertia demands faster load shedding to meet the stability requirements. In some electrical power systems in Brazil, it was found that, in the event of opening a transmission line upstream of the load shedding substation, some under frequency relay may operate improperly. This paper proposes a new method to avoid the unwanted operation of load shedding schemes when the utility substation (source) is out of service. The proposed method monitors negative sequence voltage, frequency and its rate of change, enabling faster load shedding (high dependability) without unwanted (high security) operation when compared with traditional methods. Events were classified by linear discriminant analysis and tested in the IEEE 9 bus test system. The tests consisted of several disturbances such as loss of generation and line outages at different levels of feeder loading, reactive compensation and distributed generation. The proposed method reached a 100% rate of correct classification.

Adaptive Underfrequency Load Shedding design based on generation losing estimation using Artificial Neural Network method

Under Frequency Relay (UFR) is used to prevent the frequency instability of a generation outage by balancing the load with the supply. The approach of this paper is to design an Adaptive Under Frequency Load Shedding (AUFLS) model in power system simulation software by estimating the magnitude of losing generation using artificial neural network (ANN) based on the early response of frequency after the disturbance occurred then the shed loads will be obtained based on this value estimation. The New England IEEE 39 bus system is used for this dynamic simulation. There are three operation scenarios planned with different dispatches of the generators, each generator is simulated by removing it from the system then the frequency system response is used as training data for the ANN model. The analysis is performed by comparing the frequency response of the system using Conventional 4 Steps Under Frequency Relay Load Shedding (UFLS) and the Adaptive Under Frequency Load Shedding (AUFLS). The results show that the frequency response after disturbance using the Adaptive Under Frequency Load Shedding (AUFLS) revert to the initial frequency closer and faster than using Conventional 1 Steps Under Frequency Relay Load Shedding (UFLS).

Coordinated fuzzy logic‐based virtual inertia controller and frequency relay scheme for reliable operation of low‐inertia power system

Coordination between protection and control devices is crucial for maintaining continuous operation of power systems. Existing strategies suffer from improper coordination of control and protection devices. Moreover, high penetration levels of renewable energy sources result in lowering the overall power system inertia. Therefore, this paper presents a robust fuzzy-logic control (FLC) method for superconducting magnetic energy storage (SMES) in low inertia power systems. The new proposed FLC enables robust and wide operating range for SMES compared to the widely employed controllers. The proposed FLC method and load frequency control are coordinated to emulate virtual inertia. In addition, a cooperate coordination between frequency relay and proposed controller is preserved to maintain reliable operation of low inertia power systems. To prove the effectiveness of proposed coordination strategy, it has been tested with considering different load and renewable energy sources (RESs) disturbances with varying inertia level of the selected case study. The results demonstrate that the proposed FLC method can achieve robust SMES operation as virtual inertia controller (VIC) at wide operating range. Moreover, cooperative operation of VIC and frequency protection is preserved using the proposed coordination strategy. The power system availability, frequency regulation, and dynamic stability are improved using the proposed method.

Variable frequency response testbed to validate protective relays up to 20 kHz✰

Microgrids operate in islanding or utility grid mode. In islanding mode, distributed energy sources with power electronics inverters can generate fault currents over a wide range of frequencies. To gain a better understanding of the nature of these events, it is crucial to measure currents at frequencies of up to 20 kHz at transient states with protective relays. Protective relays at these frequency responses should be tested prior to being installed in microgrids. However, testing at high-frequency currents cannot be done with Relay Test Equipment (RTE) that generate signals up to 50th Harmonic for 60 Hz (3 kHz). In this study, a frequency response method and testbed for high-frequency currents of up to 20.16 kHz was developed and tested. The testbed utilized a RTE and High-Frequency Power Source/ Amplifier. Frequency relay experiments were run at frequencies of up to 1 and 20.16 kHz at a current magnitude of 0.1 and 0.5 A, respectively. The events were collected, and the current magnitude and frequency were plotted at time and frequency domain, respectively. The study of current magnitude and frequencies of up to 20.16 kHz for two overcurrent relays was performed and validated the variable frequency testbed and methodology.

Dynamic ambient HetNet for hybrid data communication and transmission in IoT networks

In this manuscript, the Dynamic ambient HetNet for hybrid data communication and transmission in IoT networks is proposed. The lodging of colossal devices and their linkages in and beyond 5th generations (5G) has obtained a great deal of studies from academia and business. In the macro hotspot field, the uses of emerging Device-to-device (D2D), Light Fidelity (LiFi), Unmanned Aerial Vehicle (UAV) and Drones can’t simply cross the paths of transient network support prerequisites. Environmental interaction is an optional way to efficiently reduce this problem through the provision of urgent connections among limited-power servers. In addition, the effectiveness of transmission relies on parameters and range from factors like signal form, Radio frequency (RF) origin and the atmosphere, i.e. indoor or outdoor. The proposed Dynamic Ambient HetNet architecture both indoors and outdoors, where a source node is connected to the target node via radio frequency-powered relays to increases network coverage and enhance the efficiency of mobile devices either within the macro hot spot region or during the disaster area like hurricanes. This method can exploit the Wireless interweave down-convert up-convert protocol with energy-collection capacity for simultaneous information and power transfer. During the propagation from the origin node, radio frequency-powered relay can monitor hybrid data broadcasts, owing to its full duplex features. The efficiency assessment in MATLAB demonstrates the traditional models for radio frequency relay in hybrid communication. Moreover, we endow with the challenges in relation to the ambient backscatter communication network. The experimental results proved that the proposed method is better in terms of power factor and throughput gives 90%, ratio for the uplink and down link in terms of cell load has obtained 75%, and packet throughput in terms of speed has the value of 93%.

Аналіз роботи реле частоти із застосуванням цифрової системи тестування

We were given the task of automatically checking the characteristics of the digital frequency relay. To test and configure complex devices of relay protection and automation, which are digital frequency relays, there have been used special technical means using digital technology. Therefore, this problem is solved by creating algorithms to verify the characteristics of the operation of the typical and special characteristics of the digital frequency relay. On the basis of algorithms the specialized module of check of the frequency relay which became a subsystem of domestic digital test systems of check of devices of relay protection and automatic equipment “RZA-Tester”, “Relay-Tester” and “RTS-M” is created. The developed module allows to check almost all characteristics of the domestic digital frequency relay of the URCH-3M series in the modes of automatic frequency unloading, frequency automatic restart, automatic frequency unloading with blocking on speed of decrease in frequency, control of speed of decrease in frequency. The functional unit of the specialized module allows to check all the characteristics of the frequency relay in one cycle and significantly reduce its testing time. The frequency relay test module showed high efficiency at the stage of manufacturing the URCH-3M series frequency relay on the technological lines of the RELSIS research and production enterprise and during the adjustment of the frequency relay in the power systems of Ukraine.