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Renewable energy sources are commonly available on earth; thus, both research and practical applications have drawn significant interest. In the large-scale renewable energy system, power quality in the grid, particularly harmonics and flickers, has a massive influence on the grid system. Recent years have seen enormous use of magnetically controllable reactors (MCRs) to solve these power quality problems. MCR can provide reactive power and voltage regulation in ultra and high voltage power grid, suppress power frequency and overvoltage operation, eradicate generator self-excitation, dynamically adjust power charging in a transmission line, suppress secondary arc current, damping system resonance, and so on, which can meet the different needs of the modern system. Considering MCR’s development status, this paper provides a detailed theoretical analysis of MCR and its configurations.Moreover, voltage and reactive power control mechanisms and other associated economic and technical factors and relevant application selection are explained in detail. It aims to give the researchers and application engineers dealing with power quality issues a broad perspective on MCR technology’s status. Finally, the MCR issues and future directions for research are discussed. A list of more than 280 research publications on the subject is also linked for a quick reference.

Power systems are categorized as nonlinear dynamical systems, and the importance and complexity associated with their stability have dramatically increased. Accordingly, the behavior of power systems can be characterized by interactions between continuous and discrete-event dynamics. This paper proposes a systematic approach to the design and analysis of a supervisory control scheme for power systems using the hybrid automata (HA) model. The proposed model for optimal controller application is derived, and the power system's overall behavior is modeled using HA to enhance its stability. Hybrid systems' formulation incorporates continuous dynamics as well as discrete switching behavior into a modeling and control framework, thus allowing a complete system description while crystallizing the concepts of safety into system design criteria. This study uses a power system HA model as a discrete event system (DES) plant and controller. In the proposed method, to present the hybrid model, the discrete events used include the presence and absence of disturbances and voltage control elements, fault, sudden load increase, capacitor bank, and under-load tap changer (ULTC) transformer. Voltage stability and control are investigated by the generators’ rotor angle, bus voltage, eigenvalues, and the stability theory of the switched linear systems. Applications in voltage control, stability, and dynamic service restoration are presented on two benchmark power systems with 12 discrete states. The simulation results reveal the effective performance of the proposed supervisory controller model to enhance voltage stability in power systems.

This paper proposes a Multi Object Particle Swarm Optimization (MOPSO) to find the optimal location and capacity of Distributed Generation and D-STATCOM device. The objective function has adapted with a multi -objectives function to improve voltage profile, the voltage stability and reduce the total power loss of the Radial Distribution System (RDS). Basically, the voltage stability index (VSI) has been used to pre-determine the optimal location of DG and D-STATCOM. Then, a MOPSO applies to achieve the suitable size of DG and D-STATCOM units with different load models. The proposed method is compared with other existing methods and it was obtained losses reductions and enhancement voltage stability and average voltage when was tested on IEEE 33-bus and real Iraqi 65-bus radial distribution system through simulation using MATLAB. Furthermore, different cases were considered for using the (MOPSO) algorithm at different load factors.

Identifying the weak buses in power system networks is crucial for planning and operation since most generators operate close to their operating limits, resulting in generator failures. This work aims to identify the critical/weak node and reduce the system’s power loss. The line stability index (Lmn) and fast voltage stability index (FVSI) were used to identify the critical node and lines close to instability in the power system networks. Enhanced particle swarm optimization (EPSO) was chosen because of its ability to communicate with better individuals, making it more efficient to obtain a prominent solution. EPSO and other PSO variants minimized the system’s actual/real losses. Nodes 8 and 14 were identified as the critical nodes of the IEEE 9 and 14 bus systems, respectively. The power loss of the IEEE 9 bus system was reduced from 9.842 MW to 7.543 MW, and for the IEEE 14 bus system, the loss was reduced from 13.775 MW of the base case to 12.253 MW for EPSO. EPSO gives a better active power loss reduction and improves the node’s voltage profile than other PSO variants and algorithms in the literature. This suggests the feasibility and suitability of EPSO to improve the grid voltage quality.

In recent years, power systems have undergone major changes called energy transitions during which synchronous generators have been replaced with power electronics-based generation. Therefore, the voltage stability of power systems has become a major concern owing to the absence of synchronous generators. This study proposes multi-objective optimization using the non-dominated sorting genetic algorithm III to achieve optimal reactive power reserve procurement and improve the voltage stability of the overall system. These systematic approaches require high computational power and are unsuitable for the operational frameworks currently used for large-scale power systems. Previous works have rarely considered the local characteristics of reactive power or generation de-commitment with sufficient re-dispatch owing to greater renewable energy integration. We propose a framework for achieving systematic optimization by considering various objective functions while utilizing the regional aspect of reactive power via spectral clustering-based voltage control area (VCA) identification. The proposed method comprises systematic and regional approaches to optimizing systems for voltage stability improvement based on VCAs. The results demonstrate that the proposed method shows satisfactory performance. These results will be helpful for decision making for power system operations in harsher environments with more renewable energy.

These days, with the significant increase in the use of renewable energy sources as additional energy sources connected to the distribution network, many challenges and difficulties arise in ensuring sustainability and reliability. The generation, transmission and distribution, in the current state of the electricity system, are facing quite dynamic changes. They are the result of the liberalization of the energy market, the increased use of renewable energy sources such as photovoltaic systems, wind turbines and the charging stations for hybrid and electric vehicles. The most important factors are related to the balancing of the energy system, the analysis of voltage stability, overcoming the consequences of the increase in short-circuit currents, increasing the transmission capacities of the system forming and distribution networks, as well as the accurate forecasting of the development of loads and consumption over the coming years. This article presents an analysis of the voltage stability in a smart microgrid for two different scenarios. The studied cases describe a linear low-voltage p-type microgrid with loads connected to it at different nodes. Data on the type and cross-section of the conductors of the studied power line are presented. Simulation studies were carried out to determine the limits of grid voltage stability when connecting photovoltaic plants with a set power. The simulation results are commented on and an analysis of the optimal operating mode of the system is realized. The model studies were implemented in the NEPLAN program environment. The research carried out allows an evaluation of the permissible limits for network stability when connecting photovoltaic plants. Through this evaluation, it can be determined how many and at which node the loads should be connected without causing an imbalance in the network. This is useful from the point of view of ensuring the sustainability and reliability of electrical energy in a microgrid.

This letter proposes a concept to discriminate an electrical fault from a cyber attack in the modern power system. A cyber attack factor is introduced which may mislead the bus voltage stability virtually at load buses. The proposed cyber attack models are validated by executing multiple cyber attacks at a time on Western system coordinating council (WSCC) 9 bus test power system by using Siemens PSS/E and MATLAB softwares. Further, the impact of electrical fault and cyber attack on the WSCC 9 bus test power systems voltage stability has been analysed to develop a discrimination algorithm in reference to chosen load index. Despite its simplicity, the proposed discrimination algorithm is robust, accurate and quite suitable to develop intelligent measures for mal-operations against cyber attacks in the smart electric grid. [ABSTRACT FROM AUTHOR]

Smart electric grids are practising flexible, reliable and robust operations during delivery and consumption of power. However, these grids are highly vulnerable to a wide range of cyber attacks due to the deployment of an extensive communication network. In this paper, the nature of cyber attack on given power system based on proposed cyber attack models and theorems is analysed by utilizing steady state voltage stability (L index). Further, a cyber attack factor is introduced which may mislead the bus voltage stability virtually. The proposed cyber attack models and theorems are validated by executing cyber attacks on WSCC 9 bus and IEEE 14 bus test systems by using Siemens PSS/E and MATLAB softwares. Through the proposed theorems, the paper exposes and quantifies the threat of cyber attacks in the electric power grid. The simulation results reveal that the proposed cyber attack models may misrepresent the bus voltage stability, thereby misleading the energy management centre (EMC) operator into taking incorrect countermeasures. The above incorrect actions may force voltage instability which further leads to major interruptions in the electric power supply and possible cascading failure of the electric power grid. Moreover, the proposed theorems and rigorous simulations presented in the paper support the EMC operator in intelligently identifying a cyber attack, thereby enabling development of appropriate corrective actions during such cyber attacks on the smart electric grid. Thus, the concept of proposed methodology could best assist the power system operator to build detection algorithms for discrimination of cyber attacks from electrical faults towards strong electric grid resilience character. [ABSTRACT FROM AUTHOR]

This paper introduces a new model for optimal wind distributed generation (WDG) allocation based on mixed integer linear programming (MILP) in todays' smart grids considering on-load tap changing (OLTC) and power factor control (PFC) strategies. The objectives of the proposed optimization model are improving voltage stability and energy loss minimization subject to power flow constraints, line thermal limits, maximum number and size of WDG units, penetration limit, discrete OLTC tap position constraints, and PFC constraints. An efficient voltage phasor-information-based probabilistic voltage stability index (VSI) is extracted to measure the improvement of voltage stability with WDGs. Besides energy losses, reduction index is used to measure the energy loss reduction with the integration of renewable WDGs in the distribution system. An efficient linearized power flow (LPF) model as well as piecewise linearized model of the quadratic terms associated to the PFC constraints are represented to convert the original nonconvex problem into the form of a well-known MILP problem, which guarantees optimal solution and computationally is efficient to be solved using powerful commercial solvers. The effectiveness and validity of proposed model is investigated in compared to the state-of-the-art population-based methods and classical models. [ABSTRACT FROM AUTHOR]

Electric springs (ESs) are novel electric-power devices that alleviate power-quality problems such as voltage fluctuations induced by grid access to renewable energy resources. However, with the continuous increase of uncertain factors such as parameter perturbation and external disturbance, the environment becomes more complicated, so traditional linear controllers for ESs are finding it increasingly difficult to meet the control requirements due to narrow stability regions, low precision, and poor robustness. To overcome this problem, we propose herein a control method that combines adaptive control and sliding-mode control and apply it to ESs. First, an inexact model of the ES system was established and analyzed. Next, an ES control system was designed based on adaptive sliding-mode control, and then the asymptotic stability of the closed-loop system is proven. Finally, the proposed control system was verified through a MATLAB simulation. The results show that adaptive sliding-mode control not only ensures the voltage stability of critical loads in the microgrid but also resists the influence of parameter perturbation and external disturbances, leading to better steady-state and dynamic performance than a linear controller. [ABSTRACT FROM AUTHOR]

The large-scale integration of renewable generation and the gradual decommissioning of conventional power plants has led to decreased availability of resources for providing services and support to the bulk transmission grid. This paper presents a novel methodology for providing support to the bulk transmission system through the control of thousands of small distributed energy resources (DERs), located in distribution systems. This control scheme is expected to serve jointly with other classical countermeasures against instability conditions. The proposed method is model-free, scalable, and does not rely on extensive communication infrastructure. It integrates an online method (New LIVES) to monitor the voltage stability status of the transmission system, a rule-based decentralized decision algorithm, and the local DER mechanisms implementing the control actions. The proposed approach is implemented on a combined transmission and distribution test system with over 4200 low-voltage buses and the dynamic simulation results illustrate its flexibility, practicality, and tractability. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Power flow reliability, voltage security and transmission congestion management are paramount operational issues in a power system. Flexible AC transmission system (FACTS) controllers are suitable technologies that can provide compensation and dynamic control of power system transmission parameters to enhance effective performance and reliability. The interline power flow controller (IPFC), if optimally placed, can regulate the impedance of multiple lines to improve active power transfer capacity and voltage profile. This study examines the performance of IPFCs for voltage enhancement by suppressing fluctuation. A modified Newton–Raphson load flow problem with an incorporated IPFC variable has been formulated with the objective to improve voltage stability and maintain active power flow. The effectiveness of the proposed method was tested on the Nigerian 41 bus transmission network. The obtained result of the system with an IPFC placed at the weakest bus of the network was compared with Newton–Raphson load flow analysis of the same network without an IPFC. The results of load flow analysis for Case 1 (the system without an IPFC) showed that the transmission network without an IPFC had a real power loss of 4.699488 p.u., and reactive power loss of 4.467413 p.u., whereas the integration of an IPFC to the power flow formation in Case 2 resulted in the reduction in the transmission network's overall losses to 0.55297 p.u. and −38.3329 p.u. The modified method proves effective as the power system network with an IPFC returns a more stable voltage profile and improves active power flow. In addition, this method, similar to all other mathematical optimization approaches, returns a strong accurate result but may be a drawback in terms of longer computational time compared with metaheuristic methods which are preferred for a larger network system. [ABSTRACT FROM AUTHOR]

With the large-scale integration of wind power, the voltage stability problem in the power system has become increasingly prominent. Therefore, this paper studies the maximum penetration ratio of wind power from the perspective of voltage stability. Firstly, the mathematical grid-connection model of the wind generator is established. Secondly, using the impedance modulus margin index (IMMI) and the Thevenin model, the analytical calculation method for maximum wind power penetration under the voltage stability margin constraint is proposed with theoretical derivation. Then, a typical case study is used to verify the feasibility and effectiveness of the proposed method. Finally, based on this, the key factors affecting the wind power penetration limit are analyzed from the source–grid–load side, and practical engineering measures to improve the maximum penetration ratio of wind power are summarized. This research will be helpful for the planning and operation of the high-proportion renewable energy power systems. [ABSTRACT FROM AUTHOR]

Performance analysis is challenging in modern power distribution networks due to the increasing penetration of distributed energy resources (DERs) interfaced by voltage source converters (VSCs). Parameter uncertainty, black-box models of the components, and low inertia are some of the issues that must be addressed. The latter can represent high vulnerabilities to sudden load changes in a microgrid (MG). Additionally, the islanded operation represents a challenge for inverter-based (DERs), where secondary control must regulate the microgrid frequency and voltage to its nominal values. When a secondary control strategy is implemented, it is necessary to validate its performance under several conditions. Most existing research papers focus on the microgrid's small-signal and transient stability. At the same time, little has been done on the influence of the load model on voltage stability. This type of analysis is required to ensure an adequate transition between the grid-connected and stand-alone modes. This paper provides a voltage stability analysis of a microgrid, considering secondary control based on receding horizon and frequency-dependent load models. Simulation results demonstrate the robust performance of the secondary control and validate the importance of considering or adapting voltage stability indices to ensure adequate microgrid performance. [ABSTRACT FROM AUTHOR]

The strength concept is an important tool for voltage stability evaluation of emerging hierarchical-infeed LCC-UHVDC (HIDC) systems. However, the complex inter-inverter interactions in such systems have caused significant difficulties for the strength assessment. This makes the accuracy of earlier strength assessment indices limited due to empirical analysis rather than rigorous theoretical reasoning. Thus in this paper, the hierarchical-infeed voltage interaction factor (HVIF) index is firstly utilized to quantitatively depict the complex inter-inverter interactions in HIDC systems. The use of the HVIF enables these interactions to be effectively incorporated into the subsequent strength assessment by proposing the hierarchical-infeed interactive effective short-circuit ratio (HIESCR) strength index. The critical HIESCR (CHIESCR) defined to delineate the voltage stability limit also evaluates to consistently 1.0 such that the distance between the HIESCR and CHIESCR is naturally an accurate stability margin. Since the HIESCR is developed based on the rigorous theoretical reasoning, it is more accurate than earlier indices for voltage stability evaluation. Moreover, the parametric dependence analysis of the HIESCR versus various system parameters and rated operation variables is conducted. This offers a comprehensive perspective for better understanding of the strength variation characteristics. Finally, case study in the modified IEEE 118-bus system validates the HIESCR. [ABSTRACT FROM AUTHOR]

Nowadays, flexible alternating current transmission system devices, particularly unified power quality conditioner (UPQC) are found to have significant impacts on stability of rising power system. In power systems, several intellectual optimization methods were exploited to position the UPQC. However, those optimization models fail to offer more reliability and feedback signal. Hence, this paper presents a power quality improvement model, which is based on a hybrid algorithm that links genetic algorithm (GA) and DragonFly algorithm (DA). In the current research work, the optimal solution is determined based on the crossover operation of GA in dragonfly algorithm (DA), and hence, the adopted model is named as Genetically Modified DA algorithm. Moreover, the proposed model discovers the optimal location of UPQC device by focusing on the UPQC cost, power losses, and Voltage stability Index. The proposed model is carried out in IEEE 69, and IEEE 33 test bus systems. In addition, the performance of implemented model is distinguished over other conventional models such as artificial bee colony, firefly, grey wolf optimization, whale optimization algorithm, worst solution linked whale optimization algorithm update (WS-WU), GA and DA. The performance of the proposed model is effectively proved by performance and convergence analysis. [ABSTRACT FROM AUTHOR]

The traditional black-box Thevenin equivalent method cannot analyze the influence mechanism of wind power integration on Thevenin equivalent parameters. With the increase in wind power penetration, it will be difficult to accurately assess the voltage stability of power systems with wind power. Therefore, a Thevenin equivalent analytical method is proposed to analyze the voltage stability of a power system with wind power. This method adopts the equivalent model of wind power integration based on the current source model. It establishes the Thevenin equivalent analytical model for power systems with wind power by dividing the node types. Then, the analytical expressions of the Thevenin equivalent parameters are derived based on two equivalent modes to characterize the mechanism of wind power integration on the Thevenin equivalent parameters. In addition, the calculation flow chart of the voltage stability criterion is formulated based on the analytical value of the Thevenin equivalent impedance under different load growth ratios and wind power penetrations. Finally, a case study is conducted on the improved IEEE 39 node system with wind power. The results demonstrate the feasibility and effectiveness of the proposed Thevenin equivalent analytical method, which can more accurately judge the voltage stability of the power system with wind power. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The computing infrastructure to support the power grid monitoring and control evolves with the increasing system complexity and integration of distributed energy resources (DERs). The integration of DERs requires a stability assessment application to monitor and control at a faster rate compared to the legacy system. Distributed computing architecture provides opportunities for managing these key changes by introducing solutions within substation computers and digital devices such as phasor measurement unit. The proposed decentralized voltage stability using a distributed coordination platform is a secondary emergency control mechanism utilizing large amounts of data in real-time for faster monitoring and control with the legacy system. The developed algorithms have been validated using the IEEE 30, 57, 118, and 300 bus systems using offline and real-time hardware-in-the-loop testbed modeling and simulation. To demonstrate the flexibility of the distributed coordination blocks, multiple case studies and implementation are presented. With control decisions required under changing operating conditions, the IEEE 30 bus system is simulated in real-time using a digital simulator and a network simulator (NS-3). The impact of the SYN flood cyberattack and tolerance of the computing infrastructure to resulting missing data have also been illustrated. [ABSTRACT FROM AUTHOR]

The passive power distribution networks are prone to imperfect voltage profile and higher power losses, especially at the far end of long feeders. The capacitor placement is studied in this article using a novel Mine Blast Algorithm (MBA). The voltage profile improvement and reduction in the net annual cost are also considered along with minimizing the power loss. The optimization problem is formulated and solved in two steps. Firstly, the Voltage Stability Index (VSI) is used to rank the nodes for placement of the capacitors. Secondly, from the priority list of nodes in the previous step, the MBA is utilized to provide the optimal location and sizes of the capacitors ensuring loss minimization, voltage profile improvement, and reduced net annual cost. Finally, the results are tested on 33 and 69 radial node systems in MATLAB. The results for the considered variables are presented which show a significant improvement in active and reactive power loss reduction and voltage profile with lesser reactive power injection.

Voltage stability in power systems has become an important problem in planning of power systems due to both power quality and regional black out. This problem is known in the literature as a nonlinear optimization problem with multi-constraint function. In this study, a new algorithm, named as Electrically Charged Particle Optimization (ECPO), is proposed in the problem of improving voltage stability at Optimum Power Flow (OPF) problem. The efficiency of the ECPO algorithm was tested by applying the IEEE 30 test bus system, which is the most used in the literature. The test results were then compared with other methods reported in the literature to show that ECPO provides an effective and high quality solution for OPF problem.

Bu çalışmada, çok baralı bir güç sisteminin herhangi bir yük barasından görülen Thevenin empedansı ve yük empedansı kullanılarak yük barasına gerilim kararlılığı değerlendirmesi yapılmıştır. Gerilim kararlılığı analilizi yapılacak baradan görülen Thevenin eşdeğer devre empedansı optimizasyon esaslı bir yaklaşımla hesaplanmıştır. Optimizasyon yaklaşımı için yerel baradan sadece akım, gerilim ve güç faktörü ölçümleri yapılmıştır. Hesaplanan Thevenin eşdeğer devre empedansı ve baradaki yükün empedansı ile baraya ait empedans kararlılık indeksi hesaplanmıştır. Hesaplanan empedans kararlılık indeksi, baranın gerilim kararlılığı durumunu gerçek zamanlı olarak takip etme imkanı sunmuştur. Önerilen yaklaşımla elde edilen Thevenin empedansı ile hesaplanan empedans kararlılık indeksine karşılık gelen kritik güç değeri ve güç akışından elde edilen kritik güç değerinin birbirine çok yakın olduğu görülmüştür.

In this paper, analysis and ranking of singlecontingency due to the outage of transmission lines for a large scale power system of the Kurdistan Region (KR) are presented. Power System Simulator software (PSS®E33) is used to simulate the Kurdistan Region power system network and perform the contingency analysis for single line outage. This analysis is essential in order to predict and evaluate the voltage stability in case of contingency occurrence to know the most severe case and plan for managing it. All possible transmission line outages of the network are tested individually. After each branch disconnects, load flow analysis areapplied by using Newton Raphson method then all bus voltages are recorded, and compared with them before the contingency. Voltage performance index is calculated for all possible contingencies to rank them according to their severity and determine the most severe contingency which is corresponding to the highest value of performance index. Also,the contingencies which cause load loss and amount of this load are observed.

Sustainable energy resource implementation has several advantages in terms of energy efficiency, reliability, and resilience. However, there are still challenges with the power quality in suitable energy balance and acceptable voltage levels in the electrical network. Therefore, this study presents novel energy coordination for implementing grid-tied microgrids, including photovoltaic and battery energy storage systems. Thus, multi-agent modelling based on system analysis is implemented to formulate the dynamic performance of independent, interconnected and autonomous microgrids. Three optimal control schemes, including open-loop, closed-loop and model predictive control, are combined with the optimal power flow algorithm to dynamically coordinate each independent agent and the entire microgrid. The system results demonstrate that, by combining these strategies with several smart homes, the dynamic coordination of microgrids brings various benefits, such as important economic, environmental and operation performance indicators, voltage stability, power loss minimisation and power-saving. The validation of the designed approaches is bench-marked within a 33-bus IEEE network in the residential sector. The developed intelligent coordination structures achieve significant energy savings ranging from 23.99% to 36.14% while maintaining suitable system voltage levels and minimising power loss. Besides, the developed dynamic coordination offers an adequate scalability framework for an effective microgrid implementation. [Display omitted] • Implement a real-world demand management model for residential applications. • Formulate tertiary control strategies based on EMS and MAS for optimal coordination of microgrids. • Coordinate distributed energy resources, including solar PV and energy storage tied to the grid. • Employ a dynamic approach to ensure efficient utilisation of available energy resources within smart microgrids. • Provide a microgrid KPI framework based on techno-economic and environmental assessment. [ABSTRACT FROM AUTHOR]

ABSTRAK Peningkatan kebutuhan listrik tanpa ada penambahan sumber listrik yang terus menerus akan mengakibatkan masalah pada voltage stability. Untuk menyelesaikan masalah tersebut dengan penerapan energi terbarukan yang memungkinkan adalah model pembangkit tersebar / Distributed Generation (DG). Penyulang Watu Ulo Jember merupakan penyulang kelistrikan 10,03 KV 75 bus yang bertempat pada Jember bagian selatan dimana potensi energi terbarukan dapat dilakukan. Pada penelitian ini optimasi penempatan DG dengan level penetrasi dilakukan untuk mengetahui kenaikkan pembebanan kelistrikan yang maksimal (loadability) pada penyulang Watu Ulo Jember dengan mempertimbangan faktor perbaikan level tegangan menggunakan algoritma PSO. Penelitian ini diharapkan salah satunya dapat menjadi kajian ilmiah pemerintah kabupaten Jember terhadap potensi pemasangan DG untuk meningkatkan loadability dalam pemenuhan kebutuhan beban pelanggan listrik. Kata kunci: Energi Terbarukan, Pembangkit Tersebar (DG), Loadability, Algoritma PSO, Voltage Stability. ABSTRACT The increase in electricity demand without the addition of a continuous power source will cause problems in voltage stability. To solve this problem with the application of renewable energy that is possible is the Distributed Generation (DG) model. The Watu Ulo Jember feeder is a 10.03 KV 75 bus electricity feeder located in the southern part of Jember where the potential for renewable energy can be carried out. In this study, an optimization of DG placement with penetration level was carried out to determine the maximum increase in electrical loading (loadability) on the Watu Ulo Jember feeder by considering the voltage level improvement factor using the PSO algorithm. It is hoped that this research can become a scientific study of the Jember district government on the potential of installing DG to increase loadability in meeting the needs of electricity customers. Keywords: Renewable Energy, Distributed Generation (DG), Loadability, PSO Algorithm, Voltage Stability.

The critical challenge for an efficient islanding operation of a distribution system having Distributed Generation (DG) is preserving the frequency and voltage stability. Contemporary load shedding schemes are inefficient and do not adequately assess the optimum amount of load to shed which results in either excessive or inadequate load shedding. Hence, this paper presents an optimal load shedding technique using Chaotic Slime Mould Algorithm (CSMA) with sinusoidal map in order to achieve greater efficiency. A constrained function with static voltage stability margin (VSM) index and total remaining load after load shedding was applied to accomplish the evaluation. A total of three islanding scenarios of IEEE 33 bus and IEEE 69 bus radial distribution systems were used as test systems to assess the efficacy of the proposed load shedding approach using MATLAB software. To identify performance enhancements, the developed method was compared to Backtrack Search Algorithm (BSA) and the original SMA. According to the results, CSMA outperforms both BSA and SMA in terms of remaining load and voltage stability margin index values in all the test systems.

This paper proposes the maiden application of a modern meta-heuristically optimised fractional order PID (FOPID) controller for ensuring the voltage stability of a DC microgrid system having PMDC generator coupled to a solar dish-Stirling engine. A significant cost reduction and efficiency enhancement can be achieved by the proposed topology. Popular meta-heuristic optimisation algorithms such as grey wolf optimiser (GWO), mine blast algorithm (MBA) and particle swarm optimisation (PSO) are adopted for tuning the gain constants of the controllers. The major focus of this article is to keep the common DC bus voltage of the microgrid at the desired steady-state value under varying load and varying solar insolation conditions. The results demonstrate the superior performance of the proposed controller.

In this era of Internet every electronic device being manufactured comes with built-ins to connect itself with the Internet. Such electronic gadgets create a massive amount of traffic flows every second. Managing this immense Internet traffic has become an exhausting job. Classifying these massive flows of data and interpreting them has attained considerable importance in the sight of researchers and Internet Service Providers. Many methods have been presented by various researchers to address this classification issue. This paper presents a Hybrid Classifier algorithm, which is a combination of the well-known machine learning types; the supervised learning and unsupervised learning to solve this classification issue. Accurate and Efficient recognition of flows is the key to manage flows in real-time. This algorithm classifies the traffic flows into real time flows and non-real time flows. It uses the built decision support model for classifying the flows based on the target class. To further validate the classification, it applies the k-means model. A significant improvement in the classification accuracy has been obtained.

Local reactive power control in distribution grids with a high penetration of distributed energy resources (DERs) will be essential in future power system operation. Appropriate control characteristic curves for DERs support stable and efficient distribution grid operation. However, the current practice is to configure local controllers collectively with constant characteristic curves that may not be efficient for volatile grid conditions or the desired targets of grid operators. To address this issue, this paper proposes a time series optimization-based method to calculate control parameters, which enables each DER to be independently controlled by an exclusive characteristic curve for optimizing its reactive power provision. To realize time series reactive power optimizations, the open-source tools pandapower and PowerModels are interconnected functionally. Based on the optimization results, Q(V)- and Q(P)-characteristic curves can be individually calculated using linear decision tree regression to support voltage stability, provide reactive power flexibility and potentially reduce grid losses and component loadings. In this paper, the newly calculated characteristic curves are applied in two representative case studies, and the results demonstrate that the proposed method outperforms the reference methods suggested by grid codes.

Wind power generation is one of the mainstream renewable energy resources. Voltage stability is as important as the frequency stability of a power system with a high penetration of wind power generation. The advantages of high-voltage direct current (HVDC) transmission systems become more significant with the increase of both installed capacity and transmission distance in offshore wind farms. Therefore, this study discusses various voltage control methods for wind turbines and HVDC transmission systems. First, various voltage control methods of a wind farm were introduced, and they include QV control and voltage droop control. The reactive power of a wind turbine varies with active power, while the active power from each wind turbine may be different owing to wake effects. Thus, QV and voltage droop control with varying gain values are also discussed in this paper. Next, the voltage control methods for an HVDC transmission system, such as power factor control, voltage control, and Vac-Q control, are also summarized and tested in this study. When a three-phase short circuit fault occurs or a sudden reactive power load increases, the system voltage would drop immediately. Thus, various voltage control methods for wind turbines or HVDC can make the system’s transient response more stable. Therefore, this study implemented the simulation scenarios, including a three-phase short circuit fault at the point of common coupling (PCC) or a sudden increase of reactive power load, and adopted various voltage control methods, which aim to verify whether additional voltage control methods are effective to improve the performance of transient voltage. The voltage control method has been implemented in PSCAD/EMTDC, and the simulation results show that the QV control performs better than the droop control. In addition, when applying the voltage control technique during a three-phase fault, transient voltage nadir can be improved through either an HVDC transmission system or an AC transmission system.

• A hybrid model-data-driven framework for coordinated power system planning is proposed. • An efficient surrogate model is proposed to replace time-consuming electro-mechanical transient models. • The complexity of the surrogate model is further alleviated by generating an evaluation result as a single output. The increasing wind power penetration and proliferation of induction motor loads, of which dynamic impact cannot be revealed through steady-state analysis, bring challenges to the short-term voltage stability of modern power systems. This study proposes a hybrid model-data-driven approach for dynamic VAR source planning to enhance the short-term voltage stability of wind-penetrated power systems to reduce the computation burden of electro-mechanical transient models. Firstly, the theoretical background of Stochastic Spectral Embedding (SSE) is introduced. Then, a surrogate model for the electromechanical transient model is established using SSE following efficient expansion coefficient calculation and a designed partition strategy for the studied problem. Furthermore, a hybrid model-data-driven VAR deployment optimization model is established with 3 objectives, which is solved by a dual-population-based evolutionary algorithm (DPEA). The accuracy and effectiveness of the model are verified on a modified New England 39-bus system. Simulation results prove that the computational cost is reduced significantly in comparison with conventional model-based method without a compromise in accuracy and the proposed method is also more accurate than methods based on other surrogate models. The proposed SSE-based model can be applied to other power system analysis with electro-mechanical transient models to alleviate the computational cost. [ABSTRACT FROM AUTHOR]

The depletion of conventional fuel reserves and the high carbon emissions have alarmed the energy sector drivers. The integration of renewable energy resources (RERs) towards power system transformation is an obvious approach for a new-zero future. However, this integration also brings challenges in terms of voltage stability and power losses due to the variable output of RERs. To address these challenges, this work proposes a novel approach utilizing photovoltaic (PV) inverters and static var compensators (SVCs) for reactive power control in power distribution networks (PDNs). It enhances voltage stability and minimizes power losses. The proposed study deploys a proximal policy optimization (PPO) algorithm for real-time communication and control between reactive power devices. Performance evaluation was made on an IEEE-33 Bus system to demonstrate the effectiveness of the proposed scheme in integrating RER-based distributed generators (DGs). The proposed system achieved 68 % voltage control, keeping the voltage within a certain range of ±5 % while minimizing power losses. The proposed system also reduced the voltage out-of-control ratio to 0.044, which indicates minimum voltage deviation from the standard value. The proposed study provides a promising solution for controlling the voltage of DGs integrated PDN, which can potentially enhance the efficiency and reliability of the power system. • This paper introduces PV inverters and SVC-based reactive power voltage regulation for renewable DG-integrated systems. • Reactive power control in the DG-integrated system is adopted using Reinforcement Learning-Driven PPO. • The validation of the proposed method uses the IEEE-33 bus system to integrate RERs-based DGs and achieve PPO-based control. • The proposed method achieved 68% voltage control, reduced power loss, and reduced the voltage out-of-control ratio to 0.044. • This research compares the suggested approach to different methodologies to demonstrate its validity and applicability. [ABSTRACT FROM AUTHOR]

The integration of renewable energy sources globally has effectively reduced carbon emissions and enhanced community self-sufficiency through local resource use. However, challenges arise with higher renewables penetration, especially at local and distribution levels. Curtailment of renewables becomes necessary during peak generation intervals to ensure power quality and system stability, raising fairness concerns. This study examines the feasibility of using bankruptcy rules to address fairness concerns in renewable power curtailment in microgrid networks. Four bankruptcy rules - proportional, constrained equal awards (CEA), constrained equal losses (CEL), and sequential priority rules - are evaluated using the IEEE 33-bus system transformed into a network of five microgrids with solar and wind generators. Voltage profiles of microgrid networks in Detroit and Chicago under high renewable penetration are assessed, and bankruptcy rules are applied to curtail surplus renewable power. The fairness of each rule is analyzed using Jain's fairness index, while a usability index evaluates power usability across microgrids under different bankruptcy rules. Simulation results show that the proportional and CEA rules exhibit better fairness and equal usability among microgrids, with voltage profiles just below the upper bound. Conversely, the priority rule improves voltage profiles at the expense of fairness and equal usability. [ABSTRACT FROM AUTHOR]

Phasor Measurement Units (PMUs) are the advanced measuring devices which provide time-stamped measurements of voltage magnitudes as well as phase angles in Wide Area Monitoring Systems. These synchrophasors are exploited in this paper to develop a model-free voltage stability assessment method using randomized singular value decomposition (rSVD). Stage-1 of the proposal carries out an off-line study to (a) identify voltage weak buses to equip them with PMUs and (b) estimate the voltage stability monitor's threshold based on the largest singular value (LSV). Stage-2 proposes a temporal change detection technique to identify and isolate the disturbance samples from steady state measurement window to maintain linearity of PMU data matrix. Finally, Stage-3 proposes the use of rSVD technique in an online environment to assess the WAVS. This technique performs SVD of low dimensional PMU data matrix to make the approach computationally lighter. The performance of the proposed scheme is demonstrated on the IEEE 14-bus system and the IEEE 118-bus system. The viability of the real-time implementation of the proposed scheme is also verified by way of its Real-Time Digital Simulation on the IEEE 14-bus system. • Synchrophasor measurement based Real-Time Wide Area Voltage Stability Assessment. • Randomized singular value decomposition to reduce the computational complexity. • Proposed method is resilient to the diverse noise levels in field PMU measurements. • Accurate voltage stability assessment in case of intermittent wind power penetration. • Real-time tested via Real Time Digital Simulator and dSPACE 1104 controller board. [ABSTRACT FROM AUTHOR]

• A novel robust transmission expansion planning model is constructed considering voltage stability margin (VSM). • The third level is formulated as a bi-level model with an upper level aimed at minimizing the operation cost minus the weighted VSM. • The binary discretization and big-M techniques are employed to linearize the third level. • Due to integer variables in the third level, a nested CCG (NCCG) is employed to solve the tri-level structure. • The results verify the effectiveness of the methodological framework. Due to a persistent increase in electricity demand and the growing integration of renewable energy sources (RESs), power systems are now operating with narrower stability margins. Consequently, it becomes imperative to consider security criteria in planning studies to maintain a sufficient loading margin. This paper presents a tri-level robust transmission expansion planning (TEP) problem, in which, unlike the existing robust models that only optimize the operation cost in the third level, both operation cost and voltage stability margin (VSM) are optimized simultaneously. The third level is formulated as a bi-level model with an upper level aimed at minimizing the operation cost minus the weighted VSM, while the lower level evaluates the VSM. The duality theorem transforms the bi-level model into a single-level one, leading to an adaptive robust optimization (RO) with bilinear terms in the third level. The binary discretization and big-M techniques are employed to linearize the third level, which yields an adaptive RO with mixed-integer recourse. Due to integer variables in the third level, a nested column and constraint generation (NCCG) is employed to solve the tri-level structure. The effectiveness of the proposed approach is demonstrated through an application on the two standard systems. [ABSTRACT FROM AUTHOR]

In recent modern power systems, the number of renewable energy systems (RESs) and nonlinear loads have become more prevalent. When these systems are connected to the electricity grid, they may face new difficulties and issues such as harmonics and non-standard voltage. The proposed study suggests the application of a whale optimization algorithm (WOA) based on a fractional-order proportional-integral controller (FOPIC) for unified power quality conditioner (UPQC) and STATCOM tools. These operate best with the help of their improved control system, to increase the system’s reliability and fast dynamic response, and to decrease the total harmonic distortion (THD) for enhancing the power quality (PQ). In this article, three different configurations are studied and assessed, namely: (C1) WOA-based FOPIC for UPQC, (C2) WOA-based FOPIC for STATCOM, and (C3) system without FACTS, i.e., base case, to mitigate the mentioned drawbacks. C3 is also considered as a base case to highlight the main benefits of C1 and C2 in improving the PQ by reducing the %THD of the voltage and current system and improving the systems’ voltage waveforms. With C2, voltage fluctuation is decreased by 98%, but it nearly disappears in C1 during normal conditions. Additionally, during the fault period, voltage distortion is reduced by 95% and 100% with C2 and C1, respectively. Furthermore, when comparing C1 to C2 and C3 under regular conditions, the percentage reduction in THD is remarkable. In addition, C1 eliminates the need for voltage sag, and harmonic and current harmonic detectors, and it helps to streamline the control approach and boost control precision. The modeling and simulation of the prepared system are performed by MATLAB/Simulink. Finally, it can be concluded that the acquired results are very interesting and helpful in the recovery to the steady state of wind systems and nonlinear loads, thereby increasing their grid connection capabilities.

This paper summarizes the results of a power system stability analysis realized for the EU project OSMOSE. The case study is the electrical network of Sicily, one of the two main islands of Italy, in a scenario forecasted for 2050, with a large penetration of renewable generation. The objective is to establish if angle and voltage stabilities can be guaranteed despite the loss of the inertia and the regulation services provided today by traditional thermal power plants. To replace these resources, new flexibility services, potentially provided by renewable energy power plants, battery energy storage systems, and flexible loads, are taken into account. A highly detailed dynamical model of the electrical grid, provided by the same transmission system operator who manages the system, is modified to fit with the 2050 scenario and integrated with the models of the mentioned flexibility services. Thanks to this dynamic model, an extensive simulation analysis on large and small perturbation angle stability and voltage stability is carried out. Results show that stability can be guaranteed, but the use of a suitable combination of the new flexibility services is mandatory. [ABSTRACT FROM AUTHOR]

With the increase in the integration of renewable energy resources in the grid and ongoing growth in load demand worldwide, existing transmission lines are operating near their loading limits which may experience voltage collapse in a small disturbance. System stability and security can be improved when the closeness of the system to collapse is known. In this research, voltage stability of IEEE 30 bus test network is analyzed and assessed under continuously increasing load condition, utilizing the Critical Boundary Index (CBI); and improved with continuous integration of battery energy storage system (BESS). BESS is considered to be a hybrid combination of storage units and voltage source converter to have a controllable real and reactive power output. Security constraint optimal power flow is utilized for optimally sizing the installed BESS. It is evident from the outcome of the research that the voltage stability of the system is controlled to be above the acceptable range of 0.3 pu CBI in all lines and the system voltage is kept within the acceptable and constrained range of 0.9-1.1 pu. [ABSTRACT FROM AUTHOR]

This article formulates the distribution generation placement and the network reconfiguration problems of distribution networks (DNs) as a composite multi‐objective optimization problem by normalizing and combining the objective functions, and suggests a new rainfall optimization (RFO) based method for solving the developed problem. The RFO, a metaheuristic optimization algorithm that models the behavior of raindrops falling down from a hill towards sea, has certain drawbacks such as removal of inactive raindrops that weakens the search process, and the possibility of choosing the same raindrop as inactive throughout the iterative process. This article also introduces modifications in the RFO for overcoming its drawbacks before adopting it in the proposed method. It considers two scenarios with seven test cases for simulation study, and compares the results of two standard DNs with existing methods for exhibiting the superior performances in respect of final solution, robustness, voltage profile, and average execution time of the proposed method. [ABSTRACT FROM AUTHOR]

The overhead power line is used for the transmission and distribution of electrical power across long distances. It consists of multiple conductors mounted on poles or towers. The parameters of the overhead transmission lines (TLs) are dependent upon certain factors that are associated with bundle conductors. This research work uses a whale optimization algorithm (WOA) to calculate the overhead AC TL parameters. The proposed technique is applied to single‐phase and three‐phase AC TLs. It can be observed that within an AC TL, a change in one parameter will cause the corresponding variation in other parameters. This work has determined capacitance and inductance per unit length for three‐phase using proposed WOA algorithms at different bundle conductor arrangements. However, the study of load modeling for voltage stability is also presented. [ABSTRACT FROM AUTHOR]

Aim. A novel technique for detecting imminent voltage instability is proposed in this paper, accompanied by a novel load shedding approach to protect the system from voltage instability. Methodology. The proposed methodology utilizes the computation of nodal reactive power loss to voltage sensitivities with load increments in the system. Originality. The nodal reactive power loss to voltage sensitivity is a novel computation and is explored to detect the likelihood of voltage instability in this work. Results. If the system is experiencing an unprecedented load growth and if all the measures reach their limits, then load shedding is the last resort to safeguard the system against instability. The sudden change in nodal reactive power loss to voltage sensitivities is utilized to devise the quantity of load to be cut in the system. Practical value. The time-based simulations performed in New England 39 bus test system (NE-39 bus), the simulated results show that nodal reactive power loss to voltage sensitivities can be used as a trusted indicator for early diagnosing of menacing voltage instability and the timely implementation of load shedding developed from nodal reactive power loss to voltage sensitivities on the system ensures voltage stability. References 29, tables 1, figures 9. [ABSTRACT FROM AUTHOR]

This paper concentrates on the impacts of distributed generation (DG) placement on the radial distribution system. Distributed generation is a term that refers to the generation of energy close to the point of consumption, in order to improve the performance of the electricity grid. It is a well proven fact that if the DGs units are placed in the right place in the distribution system and operating at optimal size, it will help in reducing the line losses and improving the voltage profile and as a consequence the reliability, stability and efficiency of the electrical system are preserved. In this paper, three types of DG units are considered and both Moth-flame optimization (MFO) and Grasshopper optimization (GOA) are applied to find the optimal DG sizing for a typical radial distribution system (IEEE-85 bus radial distribution test systems). The required location of the DG unit bus is selected using the index vector method (IVM) and the voltage stability index (VSI). The obtained results show that the two algorithms produce very same values. The best result in loss reduction and minimum bus voltage is attained for the DG unit at a power factor of 0.93 when compared to other DG types. However, this requires a large DG versus the other types. [ABSTRACT FROM AUTHOR]

The adoption of a new transmission line is extremely complex because of its socio-economic problems such as environmental clearances. Thus, there is a prominence of better utility over available transmission infrastructure. The Flexible Alternating Current Transmission System (FACTS) devices can offer transmission capability enhancement, power compensation, and stability as well as voltage improvement. However, the FACTS devices have a higher penetration impact of wind generation for the dynamic stability of power networks. In this work, an efficient Intellectual Control system has been proposed to stabilize the FACTS devices placement. The Squirrel Search Optimization is adapted with an intellectual control system to enhance the steady-state voltage stability of FACTS devices. The proposed system has been evaluated with the assist of IEEE 14 and 26 standard bus systems to handle the multi-objective functions like cost, reduction in power loss, reducing risks, and maximizing user's benefit. These multi-objective functions facilitate to attain the optimal placement and load flows at various sites. The simulation can be carried out with MATLAB/SIMULINK environment and the results manifest that the proposed system outperforms well when compared with existing approaches. [ABSTRACT FROM AUTHOR]

The goal of multi-criteria decision making (MCDM) is to select the most appropriate of the alternatives by evaluating many conflicting criteria together. MCDM methods are widely available in the literature and have been used in various energy problems. The key problems studied in electrical power systems in recent years have included voltage instability and voltage collapse. Different flexible alternating current transmission systems (FACTS) equipment has been used for this purpose for decades, increasing voltage stability while enhancing system efficiency, reliability and quality of supply, and offering environmental benefits. Finding the best locations for these devices in terms of voltage stability in actual electrical networks poses a serious problem. Many criteria should be considered when determining the most suitable location for the controller. The aim of this paper is to provide a comparative analysis of MCDM techniques to be used for optimal location of a static VAR compensator (SVC) device in terms of voltage stability. The ideal location can be determined by means of sorting according to priority criteria. The proposed approach was carried out using the Power System Analysis Toolbox (PSAT) in MATLAB in the IEEE 14-bus test system. Using ten different MCDM methods, the most appropriate locations were compared among themselves and a single ranking list was obtained, integrated with the Borda count method, which is a data fusion technique. The application results showed that the methods used are consistent among themselves. It was revealed that the integrated model was an appropriate method that could be used for optimal location selection, providing reliable and satisfactory results to power system planners. [ABSTRACT FROM AUTHOR]

A modified marine predators optimizer (MMPO) is proposed for simultaneous distribution network reconfiguration (DNR) associated with the allocation of distributed generators (DGs). In the MMPO, the predator's strategies are merged to consider the possibilities for variation in the environmental and climatic circumstances. The suggested MMPO is contrasted with the standard marine predators optimizer (MPO) and genetic, harmony search, fireworks, firefly and improved sine–cosine optimizers. The proposed MMPO is validated on single and multiple objectives using 33- and 69-bus distribution systems at light, nominal and heavy loading levels. The results obtained by the proposed MMPO are compared with those obtained by the original MPO and other optimizers. The achieved simulation outputs reveal a great improvement over the standard MPO and demonstrate the superiority of the proposed MMPO for simultaneous DNR and DG allocation. [ABSTRACT FROM AUTHOR]

The use of intelligent voltage controllers makes the operation of the electrical system simpler for system operators. This work aims to propose a methodology to find voltage control actions that simultaneously keep the voltage levels within the operating limits and manage the participating generators' reactive power reserves. For this purpose, an intelligent secondary voltage control, called SVC-neural, is proposed. The proposed methodology combines optimal power flow solutions with artificial neural networks. The latter is responsible for gathering the knowledge and characteristics of the system and proposing control solutions quickly and adaptively. The application of the proposed SVC-neural resulted in reduced total system losses and adequate control of voltage and reactive power. The most significant loss reduction using the controller was 2.24%, and the smallest reduction was 0.5%. SVC-neural results show the ability to generalise and not need to solve the optimisation problem, which can often become a complex task and require a great deal of computational effort. The results also validate the proposed SVC-neural concerning its ability to reduce losses and motivate future research on intelligent controllers. [ABSTRACT FROM AUTHOR]

This study proposed a probabilistic methodology based on a confidence interval with the aim of overcoming the limitations of deterministic methods. A stability evaluation technique was required because the output variability of renewable energy can lead to instability of the distribution system. The proposed method can predict the possibility of violating stability in the future. It can also provide a theoretical basis for securing distribution system stability and improving operational efficiency by assessing the in-stability risk and worst-case scenarios. Because of steady-state analysis in the distribution system to which solar power is connected, the probability of violating the standard voltage during the daytime when PV fluctuations are severe was the highest. Moreover, as a result of a simulation of a three-phase short-circuit in the distribution system that is connected to the PV and WT, it was observed that it could violate the allowable capacity of the CB owing to the effects of the power demand pattern and output variability. [ABSTRACT FROM AUTHOR]

The integration of renewable resources into the existing power distribution system is expanding to reduce gas emissions, treat climate change and satisfy the current global need for clean energy. If the location and size of these renewable generators are determined without considering uncontrollable reactive power compensation caused by their intermittent nature, the resultant power system may suffer from system instability and decreased reliability. Therefore, the issue of optimal location and size of renewable resources attracts great attention. In this paper, a methodology is proposed to optimize the locations and capacities of distributed renewable generators installed in conventional power distribution systems. In particular, uncontrollable reactive power compensation of these renewable resources is considered in this paper and managed through the proposed methodology to ensure power system reliability and stability. As a result, the proposed methodology reminds us of the importance of reactive power compensation by performing better in power losses reduction and the robustness of voltage stability against variable reactive power compensation. [ABSTRACT FROM AUTHOR]