In this paper, a new passive islanding detection method for grid-connected inverter-based distributed-generation (DG) systems is proposed. A statistical signal-processing algorithm known as ...estimation of signal parameters via rotational invariance techniques is used to extract new features from measurements of the voltage and frequency at the point of common coupling as islanding indicators. The new features are defined based on a damped-sinusoid model for power system voltage and frequency waveforms, and include modal initial amplitudes, oscillation frequencies, damping factors, and initial phases. A set of training cases generated on the IEEE 34-bus system was used to train a naïve-Bayes classifier that discriminates islanding and nonislanding events. Cross-validation was used to evaluate the performance of the proposed islanding detection method. The results show that by using the new features extracted from ESPRIT, the classifier is capable of discriminating islanding and nonislanding events with an accuracy close to 100%.
The paper addresses the ongoing and continuous interest in photovoltaic energy systems (PESs). In this context, the study focuses on an isolated photovoltaic system with hybrid battery-supercapacitor ...storage (HBSS). The integration of supercapacitors (SCs) in this system is particularly important because of their high specific power density. In photovoltaic (PV) systems, multi-storage systems use two or more energy storage technologies to enhance system performance and flexibility. When batteries and supercapacitors are combined in a PV system, their benefits are maximized and offer a more reliable, efficient, cost-effective energy storage option. In addition, effective multi-storage power management in a PV system needs a solid grasp of the energy storage technologies, load power demand profiles, and the whole system architecture. This work establishes a battery-supercapacitor storage system (HBSS) by combining batteries and supercapacitors. The primary objective is to devise a novel management algorithm that effectively controls the different power sources. The algorithm is designed to manage the charge and discharge cycles of the hybrid battery-supercapacitor energy storage system (HBSS), thereby guaranteeing that the state of charge (SOC) for both batteries and supercapacitors is maintained within the specified range. The proposed management algorithm is designed to be simple, efficient, and light on computational resources. It efficiently handles the energy flow within the HBSS, optimizing the usage of both batteries and supercapacitors based on real-time conditions and energy demands. The proposed method ensures their longevity and maximizes their performance by maintaining the SOC of these energy storage components within the specified limits. Simulation results obtained from applying the management strategy are found to be satisfactory. These results show that the proposed algorithm maintains the SOC of batteries and supercapacitors within the desired range, leading to improved energy management and enhanced system efficiency.
As a key portion of renewable energy resources (RESs), wind energy penetration is rapidly deployed. The effects of grid faults on grid-connected wind turbines (WTs) are causing problems for wind ...energy producers. To meet the necessary requirements, additional resources and technical interventions are needed. One of these requirements is low voltage ride-through (LVRT) of doubly fed induction generator (DFIG)-based WTs. This means that DFIG-WTs must stay connected to the grid during transient grid faults and supply active and reactive power after the fault is cleared. Many techniques for improving the LVRT capability of DFIG-WTs have been developed and this paper examines them. The paper also evaluates how well they align with grid codes, and offers case studies and simulations of the selected key techniques. Lastly, this paper provides guidelines and suggested designs for the LVRT techniques for DFIG-WTs to ensure they meet local grid codes.
•A stability mapping for FSWT with FLC based PAC is presented.•The SCIG’s global asymptotic stability in the sense of the LF is given.•A strategy for driving PAC schemes based on Lyapunov ...decision-making is provided.•The proposed strategy gives guideline for manufacturers as a mode-switching trigger.•Performance assessment metrics are applied for WT to verify the LF analysis results.
Fixed speed wind turbines (FSWTs) are still commonly used due to simplicity, robustness, and the life extension programs implemented by leading WT manufacturers. However, due to the sluggish behavior of squirrel cage induction generator (SCIG) during transient and abnormal conditions, complete and fast pre-fault restoration of grid connected FSWTs has become a necessity to maintain high power quality and avoid further instability degradation. This study provides a new analytical tool to maintain stability and assess the response of FSWTs during and post fault conditions. The SCIG’s global asymptotic stability in the sense of the Lyapunov function (LF) is given whereas the stability boundaries are established via the eigenvalues of the LF and its derivative matrices. The outcomes of LF analysis provide a comprehensible stability mapping for FSWTs equipped with pitch angle control (PAC). The study considers fuzzy logic controller (FLC) and other PAC maneuvering schemes. Moreover, the performance assessment criteria based on voltage quality and WT efficiency are presented to further validate the LF analysis results. Different scenarios under various operating conditions for actual wind speed data of the onshore Zafarana wind farm (WF) with FSWT in the Suez Gulf region of Egypt are simulated using MATLAB/Simulink® platform. Based on the results, an improved reliable strategy for driving PAC schemes based on Lyapunov decision-making is proposed. This strategy presents a recommended system for the designers and manufacturers of WT and utility operators to maintain and analyze the stability of FSWTs using Lyapunov stability boundaries as a guideline.
Microgrid (MG) is not only undergoing rapid upsurge and an effective combination of distributed generations (DGs)-based renewable energy sources, but it also fulfills a significant function in ...upgrading grid infrastructure. It is necessary for DGs, during and after any disturbances in the voltage, to stay connected in order to enhance the voltage, most importantly guaranteeing the stability of the power system. In this present context, the behavior of the distributed generations control systems has a significant impact on the MG performance. This paper investigates the effect of different control schemes of the inverter-based DG unit on the stable operation of MG after the occurrence of faults that lead to islanding events. In this paper, an appropriate control strategy is proposed to enhance the fault ride-through of MG. Within the scope of the study, the MG consists of a conventional diesel generator and an inverter-based DG unit. The MG also contains several load types; RLC load as a static load and induction motor as a dynamic load. The MATLAB Simulink is used to model the MG and its inverter control schemes. In order to assure MG stability, the variations of the voltage and frequency are possessed as key references. Results indicate that the control strategies of the inverter have a strong influence on the stability of MG. Moreover, the MG configuration with the proposed FRT resists fault effects for longer durations and this enhances the stability.
The increase in electricity demand places its focus on renewable energies as sustainable energy resources. Wind energy is one of the most important green energy sources. The doubly fed induction ...generator (DFIG)‐based wind farm has now gained prominence due to its many advantages, such as variable speed operation and autonomous control of active and reactive power. When the DFIG stator windings are directly connected to the power grid, when a grid fault occurs, some unwanted high current may be produced in the rotor windings, and the protection system will prevent the rotor side converter (RSC) from operating. Therefore, voltage stability is a significant factor in maintaining the DFIG‐based wind farm in operation during grid faults and disturbances. This paper applies a static synchronous compensator (STATCOM) to restore the voltage levels of the Egyptian power grid connected to Al Zafarana‐5th stage wind farm, which is made of 100 Gamesa G52/850 kW DFIG machines. In this paper, the STATCOM is controlled by a proportional integral (PI) and is compared with a STATCOM controlled by fuzzy logic control (FLC). For simulation, the MATLAB/SIMULINK environment is used. Moreover, the simulation results show that STATCOM devices with fuzzy logic controllers improve the effects of grid faults and disturbances such as a single line to ground fault, a line to line fault, voltage sag, and voltage swell as compared with STATCOM with PI controllers. Also, STATCOM devices based on FLC improve the stability and power quality of the system and the power system restoration procedures for the existing and future‐planned wind farms.
Islanding detection is an essential protection requirement for distribution generation (DG). Antiislanding techniques for inverter-based DG are typically designed and tested on constant RLC loads ...and, hence, do not take into account frequency-dependent loads. In this paper, a new antiislanding technique, based on simultaneous P - f and Q - V droops, is designed and tested under different islanding conditions considering different load types. The behavior of frequency-dependent static loads during islanding operation is discussed. The developed antiislanding technique is designed to fully address the critical islanding cases with frequency-dependent static loads and RLC-based loads. The performance of the proposed method is tested to accommodate load switching disturbances and grid voltage distortions. Theoretical investigation coupled with intensive simulation results using the Matlab/Simulink software is presented to validate the performance of the proposed antiislanding technique. Unlike previously proposed methods, the results show that the proposed islanding detection method is robust to frequency-dependent loads and system disturbances.
Microgrid (MG) gains higher potential and plays a key role in grid infrastructure upgrade. Although MG have many benefits, its performance during fault caused islanding conditions still needs more ...attentive investigations. In this context, the MG load types and the behavior of the distributed generations (DGs) control system have the significant impact on the stability of MG. This article analyzes the influence of various control techniques of the inverter DG unit on the dynamic performance MG after fault-provoked islanding conditions. To enhance the MG stability and the quality of voltage waveform, an adapted MG configuration equipped with a low-cost switched modulated power filter compensator (MPFC) is proposed. Using MPFC alongside the inverter DG unit gives adequate solution to overcome the shortcomings of the inverter and the flexibility of the interfacing control scheme. The MG structure equipped with MPFC is simulated using Matlab/Simulink software package. A wide perspective on the simulation results indicates that the MG stability is highly vulnerable to the inverter DG control techniques. Further, the MG may lose its stable operation due to some load type characteristics. The proposed MG structure with the MPFC can withstand longer fault durations and give better stability performance especially with induction motor (IM) loads. Moreover, the MG equipped with the MPFC has the ability to keep the voltage total harmonic distortion (THD) within the acceptable limits.
This paper addresses the development of the hybrid fault current limiter and interrupting device (HCLID) which can be used successfully as an ultra-fast short-circuit protection means for low voltage ...AC or DC industrial installations. The main components of the HCLID are as follows: a solid state commutation circuit that can supply a counter current injection from a stand-by pre-charged capacitor, a saturable core reactor as limiting impedance and a fast mechanical contact switch; all are connected in parallel. Through this study, a significantly improved and simplified approach that replaces the half-controllable SCR in the commutation circuit with self-turn-off device, such as IGCT, is presented. The use of high-performance semiconductors (IGCTs) as a commutating device affords reduced recovery voltage, reduced losses, improved reliability and dynamic performance, and fast switching time (in μs). The new approach is emulated in Piecewise Linear Electrical Circuit Simulation (PLECS) and involves a fault detection using rate of current rise rather than the current magnitude and a time delay operating characteristic. The proposed control method can be simply implemented. Different fault cases have been simulated in this paper. Simulation results proved the practicability and validity of the new HCLID.
During a change in operating condition, oscillations of small magnitude and low frequency often persist for long periods of time and in some cases even present limitations on power transfer ...capability. Generators in power systems are equipped with automatic voltage regulator (AVR) to control terminal voltage. It is known that AVR has a detrimental impact upon the dynamic stability of the power system. Power system stabilizers (PSS) are widely used to generate supplementary control signals for the excitation system in order to damp out low-frequency oscillations (LFOs). In this paper proportional-derivative power system stabilizer (PD-PSS) used to damping LFO after tuning the gains of the PSS by using PSO. The damping boundary condition of PSO technique is modified to improve its performance in the tuning and optimization process. Simulation studies performed on a typical single-machine infinite-bus (SMIB) system used in MATLAB Simulink program. Assessing the performance of the proposed modified PSO based PD-PSS with Speed deviation (incrementω) as an input signal using eigenvalue analysis. The proposed PSO based PD-PSS is evaluated and examined under different operating conditions and inertia constant each one of them applied with two test cases small disturbance and short circuit. A comparative study between the proposed PSO based PD-PSS, original PSO based PD-PSS, and lead-lag PSS is done in this work. The results ensure the superiority, the effectiveness, and the robustness of the proposed PSS over the other techniques.
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