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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.

Based on the analysis of the operation characteristics of photovoltaic cells, a novel virtual synchronous generator adaptive power regulation strategy for two-stage three-phase photovoltaic system with high permeability of clean energy is proposed. By improving the maximum power point tracking process of photovoltaic cells, the variable power point tracking control of photovoltaic cells is realized, and the control effect of DC/DC converter on the output power of photovoltaic cells is fully exerted. Without additional energy storage equipment, the energy supply required for inertia support and primary regulation of virtual synchronous generator is accurately realized. Combined with inverter VSG control strategy, the control of photovoltaic virtual synchronous generator is realized.

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.

The high energy photon source (HEPS) uses the on-axial injection scheme. There are two designs in this injection scheme that are critical to the performance of the HEPS injection system. One is the strip line kicker and another is the high voltage fast pulse power supply system. In the high voltage fast pulse power supply system, the design of high voltage power supply is very important. The output voltage stability of high voltage power supply directly affects the stability of the pulse amplitude of the injection system. A high voltage power supply with high output voltage stability is designed in this paper, and the scheme is given. The correctness of the design scheme is verified by simulation experiments. A prototype is built for full test. The test results showed that the output voltage stability is lower than 58 ppm. The output voltage is 6.4 mV(f ≤ 3 kHz)/113.2 mV(f > 3 kHz). The designed high voltage power supply can fully meet the requirements of the HEPS injection system.

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.

The choice of electrolyte for supercapacitors is challenging, with voltage stability, physical properties, environmental concerns and production processes all having to be taken into account. This challenge is greater still when thinking about e-textile applications, as these devices will be in close proximity to the end user. Historically, this challenge has been overcome with sophisticated encapsulation or the dilution of traditional supercapacitor electrolytes. This work looks to challenge these norms by investigating the performance of everyday, cupboard-items as electrolytes. The performance of four electrolytes (Grenade Energy® drink, an isotonic sports drink and LoSalt® solutions) were evaluated in a single layer, activated-carbon textile supercapacitor, against a traditional electrolyte. With areal capacitances of 25.7 mF.cm−2 these electrolytes have been shown to be competitive with more traditional systems and with further refinement, could provide safe and abundant electrolytes for wearable applications.

Microgrids are increasingly affected by volatile wind energy due to the high penetration of this kind of renewable energy sources. This study investigates the impact of wind energy uncertainty on voltage stability and energy management system (EMS) of isolated microgrids in the presence of plug-in electric vehicles (PEVs). A stochastic voltage stability constrained microgrid energy management system (SVSC-MEMS) architecture based on a coordinated unit commitment-optimal power flow (UC-OPF) methodology, which simultaneously considers the UC and OPF constraints, is proposed. The proposed model guarantees the system security from the voltage stability standpoint, considering a specific loading margin. Besides, the role of PEVs in the microgrid EMS is examined. In order to validate the performance of the introduced SVSC-MEMS, a CIGRE benchmark test system is used. The numerical results, obtained from the implementation of the proposed model in the general algebraic modeling system (GAMS) environment, demonstrate the importance of voltage stability and wind power uncertainty on the microgrid EMS, and furthermore, the key role of PEVs in the emerging microgrids.

Voltage stability is the main focus in supplying the electricity power to the consumer. The power quality is important as the stability and the continuing supply is well maintained. This research aims to regulate the system voltage when the load increased with the addition of wind turbines. The simulation using Simulink/MATLAB with 2x1,5MW wind turbines connected to 2 MVA Synchronous Machine. The load is connected and increased gradually. The voltage stability can be maintained when the load is increased up to 50%. The voltage loses its stability when the load near its full capacity. The control is applied and the voltage can be maintained its stability with the addition of reactive power compensation, Kestabilan tegangan dalam penyaluran daya listrik merupakan salah satu fokus penting untuk mendukung aktifitas dalam melayani kebutuhan masyarakat yang menggunakan daya listrik sebagai kebutuhan utama saat ini. Dalam proses penggunaan daya listrik, kualitas penyalurannya menjadi penting agar kestabilan dan kekontinuannya dapat terjaga. Tujuan utama dari penelitian ini adalah untuk mengatur kestabilan tegangan pada sistem ketika terjadi pertambahan beban sehingga pengaruh pertambahan beban terhadap kualitas penyaluran daya listrik dan dengan pertambahan pembangkit listrik tenaga angin (PLTB) dapat diketahui. Simulasi pertambahan beban dilakukan untuk melihat pengaruhnya terhadap kestabilan tegangan dan pemodelan aksi pengontrolan yang diperlukanditerapkan untuk melihat pengaruhnya terhadap kestabilan tegangan Pemodelan dan analisis menggunakan Simulink/Matlab dengan simulasi pertambahan beban pada sistem. Model pembangkit listrik tenaga angin (PLTB) berkapasitas 2x1,5MW pada Simulink/MATLAB yang dihubungkan dengan Synchronous Machineberkapasitas 2 MVA. Beban dihubungkan dan dinaikkan secara bertahap. Tegangan masih cukup stabil ketika beban dinaikkan sampai dengan 50% dari kapasitas pembangkit. Ketika beban terus dinaikkan maka terjadi ketidakstabilan tegangan. Aksi pengontrolan diaplikasikan dengan menambahkan kompensasi daya reaktif untuk pembangkit listrik tenaga angin yang digunakan sehingga tegangan sistem dapat dikontrol kestabilannya.

The purpose of this research is to find the loading limit of a power system before hitting voltage instability and to assess the margin to voltage instability of a system consisting of a wind farm. An index called Bus Apparent Power Difference Criterion (BSDC) is used to find maximum loadable point. The measure depends on the way that in the region of the voltage collapse no extra apparent power can be delivered to the affected bus. The analysis is performed combination of wind power injection at different wind speeds and line outages in the network. In the feasibility and siting studies of wind farms the steady state analysis with network contingencies give the utility or the developer a sense of network condition upon the injection of power in the network. However, the extent of voltage stability impacted due to load growth in the system is not assessed. The research paper makes way to assess the impact on voltage stability margin with obtaining the maximum loadable point of the system and assessing the best suited bus to integrate a wind farm into the system.

The power grid in the capital city of Papua New Guinea, Port Moresby, still experiences problems of voltage stability and power losses due to many factors which is the common problem that most power systems continue to mitigate until today. The factors that give rise to these problems are the imbalance between generation and load and the long-distance of transmission lines. A possible solution to counteract these problems is to integrate photovoltaic systems into the power grid, especially at the load distribution network. This paper presents PV placement for Port Moresby system by using two stages, which are (1) identification of location with good irradiance then (2) determination of PV location by minimizing power losses and improving the voltage profile. This alternative approach is considered because Port Moresby city is situated in a location that is exposed to a significant amount of solar radiation of about 1976 kWh/m2 GHI annually. Therefore, this makes Port Moresby a suitable location to utilize this type of renewable energy technology. This research provides an analysis of the power flow within the Port Moresby grid through simulation using the Newton-Raphson method. The analysis and simulations are performed to identify the most sensitive buses within the system. Based on their high irradiance levels, these specific areas are identified as the best possible areas for integrating the photovoltaic system.

In the present work, a new approach for improving voltage stability by optimal location of the Flexible AC Transmission Systems (FACTS) devices has been discussed. We used Genetic Algorithm (GA) as an optimization technique to search the good placements of different FACTS systems in great electrical networks and its contribution to enhance voltage stability. Various FACTS devices were used in our study such as SVC, TCSC, SSSC, STATCOM, TCVR, TCPST and UPFC. The search of optimal parameters of those devices has been also investigated. The method presented in the paper was tested by using Matlab/environment. In addition, the proposed method has been implemented and tested on various IEEE power systems; 14Bus, 57Bus, and 118Bus. The obtained results show the validity of the proposed method.

International audience; Shunt capacitor banks (SCBs) are used in distribution systems for loss reduction, voltage stability improvement for the system nodes, and system capacity release. However, the size of these capacitors and their placement locations are design factors that have been considered as single or multi-objectives to derive maximum benefits from their installation. To find the optimal location and size of the SCBs, this study proposes the application of multi-objective salp swarm algorithms, considered at ambient temperature, in radial distribution systems. Additionally, a fuzzy-based mechanism has been utilized to identify the best-fit solution of three different objective functions. The proposed method is implemented on IEEE 15-bus and 33-bus radial distribution systems, as well as on real data taken from the Saudi Electricity Company. The results indicate improved effectiveness and higher capability of the proposed method.

Recently, renewable energy has received considerable attention worldwide due to environmental problems such as climate change. However, there are still many problems to be solved to increase the penetration level of renewable energy sources in a power system. Above all, a power system with a high renewable penetration level requires an entirely novel operational strategy and control approach to achieve reliable operation by considering the intermittency of variable renewable energy sources. This paper proposes power-sensitivities-based indirect voltage control of renewable energy generators with power constraints. The proposed method realizes seamless control of the voltage by compensating with the reactive power if the real power of the distributed generator (DG) is insufficient due to its intermittency. To achieve the proposed method, the real and reactive power references of DGs are initially operated based on the power sensitivities between generation and loads if all the DGs operate within the power constraints. However, if at least one of the DGs reaches its constraint limit, the references can be modified using other sensitivities between real and reactive power generation enabling indirect voltage control of DGs. Therefore, a high level of renewable penetration in power systems can be accomplished with the proposed method. The proposed method is verified with several case studies that are based on a microgrid with practical data from a real island power system. Verification is carried out using the power system computer aided design and electromagnetic transient including DC (PSCAD/EMTDC™) simulation software.

The aim of this research work is to develop a load shedding methodology to improve the frequency response of low inertia grids by attaining satisfactory voltage stability. In recent times, wind energy integration has considerably increased in many power grids. Consequently, conventional synchronous machines are being replaced from dispatch. Unlike traditional synchronous machines, variable speed wind turbine generators usually do not take part in frequency regulation without supplementary control mechanism. During substantial wind penetration, a power system may have a small number of online synchronous machines. As a result, synchronous inertia and governor responsive reserve significantly reduce. Under such situation, a system has to rely on load shedding as a last line of defense to rescue the system frequency following a large contingency. However, the conventional Under-Frequency Load Shedding (UFLS) strategy may lead to larger frequency deviation and higher amount of load cut in certain cases. A new load shedding methodology is presented in this paper to overcome this challenge. Unlike conventional UFLS technique, higher proportion of load shedding is applied to relatively weaker buses in terms of voltage stability in the proposed mechanism. Based on reactive power margin, which is an index to specify voltage stability, a general expression to quantify load shedding is derived. Also, the adaptability of the proposed strategy to various load levels is ensured. Later on, performances of the developed strategy are explored in a low inertia wind dominated test network. Simulations are executed considering various penetration levels of wind power and for two severe contingencies – loss of 550 MW interconnection and loss of 650 MW interconnection. Investigations reveal that the proposed load shedding methodology ensures satisfactory frequency response in all simulation cases. Also, the developed technique yields less frequency deviation and load cut compared to the conventional UFLS mechanism. Therefore, the reported load shedding scheme is found to be more competent to concurrently maintain frequency and voltage stabilities in renewable dominated power systems.

This paper proposes a predictive techno-economic analysis in terms of voltage stability and cost using regression-based machine learning (ML) models and effectiveness of the analysis is validated. Predictive analysis of a power system is proposed to address the need for faster and accurate analyses that would aid in the operation and control of modern power system. Several methods of analyses including metaheuristic optimization algorithms, artificial intelligence techniques and machine learning algorithms are being developed and used. Predictive ML models for two modified IEEE 14-bus and IEEE-30 bus systems, integrated with renewable energy sources (solar and wind) and reactive power compensative device (STATCOM) are proposed and developed with features that include hour of the day, solar irradiation, wind velocity, dynamic grid price and system load. An hour-wise input database for the model development is generated from monthly average data and hour-wise daily curves with normally distributed standard deviations. The data feasibility tests and output database generation is performed using MATLAB. Linear and higher order polynomial regression models are developed for the 8760hr database using Python 3.0 in JupyterLab and a best-fit predictive ML model is identified by analysing the coefficients of determination. The voltage stability and cost predictive ML models were tested for a 24hr input profile. The results obtained and the comparison with the expected values are furnished. Prediction of the outputs for the test data validate the accuracy of the developed model.

The power distribution’s aim is to satisfy power required at all load centre in the power distribution network with several considerations such as efficient functioning, the economy of operation, voltage stability, and carbon emission in the generation. Because of the rapid growth in electrical power utilization, there is a call for the addition of generation units. However, due to the global exhaustion of fossil fuels, concerns about the environmental impacts, and advancement in PV technologies, fixing a sufficient number of PV based, is a more promising solution than adding a centralize large generation station, to satisfy the increased electrical power demand. The novelty of the paper is that it presents an effectual solution to assure the increased demand by optimal placement and size of PV based DG. The impacts of the PV unit on the voltage contour, power loss of network and carbon emission are examined in IEEE 33 bus radial network and IEEE 30 bus interconnected network. Results show that the optimally placed DG improves stability, efficiency, and reduce the emission of air pollutants.

The intermittent nature of photovoltaic (PV) generation causes the voltage to fluctuate and may lead to instability, especially, in case of high penetration. In this paper, a methodology is proposed to control the reactive power generation of PV-inverters. The objective is to mitigate the voltage fluctuations at the point of common coupling (PCC) resulted from increasing or decreasing the active power output of PV plants which is dependent on solar radiation level. The generic PV-inverter models developed and recommended by the Renewable Energy Modeling Task Force (REMTF) of the Western Electricity Coordinating Council (WECC) is used to analyze the effect of high PV penetration on the dynamic voltage stability of distribution networks. Then, the tested distribution network with the embedded PV plants is modeled and simulated using PSS/E software. Levels of control that are built-in PV-inverters are tested in the case of normal operation and during disturbances. Comparison results show that the most suitable control methodology in case of disturbances and after fault clearance is the local voltage control. While the plant voltage control with coordinated V/Q control is the most preferable control methodology during normal operation.

The purpose of this study was to investigate a simplified distributed generation (DG) Position and Capacity Determination model (DG-PCD model) based on the coupling relationship between load distribution and voltage stability in the distribution network. First, based on the relationship between voltage stability and system equivalent impedance and the relationship between system equivalent impedance and load distribution, the relationship between voltage stability and load distribution is deduced, and the concept of influencing impedance mode is proposed and used in DG site selection. Then, build a DG-PCD model considering voltage stability, active power loss and line thermal stability margin, and use genetic algorithm (GA) to solve the model. Finally, an improved IEEE33-node system calculation example is analyzed. The results show that compared with the existing methods, the proposed method can get better results faster. This Proposed method not only simplifies the DG-PCD model, but also quantifies the relationship between voltage stability and load distribution. This provides a new reference index for the voltage control of the power grid.

The spectral properties of terahertz (THz) continuous-wave (CW) clinotrons have been studied both theoretically and experimentally. The resonant properties of clinotrons having strong influence on the spectral linewidth have been analyzed both for the frequencies below 150 GHz where resonances are determined by reflections of surface wave, and for THz tubes where resonances are caused mainly by the effect of mode transformations in oversized cavities. The influence of beam voltage ripples in THz clinotron on spectral line broadening has been studied and discussed. The clinotron spectral linewidth of 1.18 MHz has been demonstrated at 346.4 GHz with the output power of 100 mW when the output voltage stability of high-voltage power supply (HVPS) was 5 ppm.

In this study, in order to determine critical values of a load bus with respect to voltage stability, two different estimation approaches using local measurements of voltage (V), current (I) and phase angle (φ) on the relevant bus are investigated. First, Thevenin equivalent circuit parameters of the power system is estimated from local bus measurements; then, the critical voltage and voltage stability margin values required for evaluation of the voltage stability are calculated. The proposed approach has been tested on the IEEE 30 bus test system. In IEEE 30 standard test system, the data of the buses to be analyzed was acquired by setting up a power flow with MATPOWER software. The simulation results show that both approaches have successfully determined the voltage stability limits on the load buses and they can be used to evaluate the loading levels of the buses in terms of voltage stability, to determine the critical buses and to prioritize the load shedding operations., Bu çalışmada, gerilim kararlılığı açısından bir yük barasındaki kritik değerlerin belirlenmesi için, ilgili baraya ait gerilim (V), yük akımı (I) ve güç açışı (φ) yerel ölçümlerini kullanarak kestirim yapan iki farklı yaklaşım irdelenmiştir. İlk olarak, yerel bara ölçümlerinden güç sisteminin Thevenin eşdeğer devre parametreleri kestirilmiş, ardından gerilim kararlılığının değerlendirilmesi için gerekli kritik gerilim ve gerilim kararlılık marjini değerleri hesaplanmıştır. Sunulan yaklaşım IEEE 30 baralı test sistemi üzerinde denenmiştir. IEEE 30 baralı standart test sisteminde MATPOWER yazılımı ile güç akışı yapılarak incelenecek baralara ait veriler elde edilmiş ve her iki yöntem ile gerilim kararlılığı değerlendirmesi gerçeklenmiştir. Benzetim sonuçları, iki yaklaşımında yük baralarındaki gerilim kararlılık sınırlarını başarı ile belirlediği ve baraların gerilim kararlılığı açısından yüklenme düzeylerinin değerlendirilmesinde, kritik baraların tespitinde ve yük atma işlemlerinin önceliklenmesinde kullanılabileceğini göstermiştir.

The Port of Durban (PoD) is currently upgrading its existing power supply to a supply voltage of 132 kV. The existing 33 kV supply cables are old and have exceeded their designed life resulting in unplanned power outages. The existing 33 kV switchgear is old and obsolete as a result it is difficult to maintain. The existing maximum demand capacity will not be able to cater for the additional loads required for the planned expansion developments.The electrical load flow is a very important and fundamental tool for the analysis of any power systems and in the operations as well as planning stages. The electrical load flow study was conducted using PowaMaster software to analyse the behaviour of PoD’s electrical network post implementation of the new substation onto the currently existing network. In performing the electrical load flow study, load diversification is one of the critical input parameters that was considered because it is a true representation of the network behavior. The load forecasting was based on the planned developments commissioned between 2017 and 2027. The electrical load flow study was also to validate if all the new selected reticulation cables and transformers as part of the design have been correctly sized and will be able to operate reliably without compromising security of firm supply with the implementation of all the planned future loads. This report entails the results of the electrical load flow study that was conducted to analyse the voltage stability and system reliability of the PoD’s electrical network in conjunction with new 132/33 kV Langeberg Substation.

The proliferation of photovoltaics (PV) in distribution systems brings about voltage stability problems. This paper proposes an algorithm to calculate extreme bifurcation intervals considering deep PV penetration levels. The paper applies the sandglass-hyper-ellipsoid-cone model to analyze the correlations among net bus loads representing bidirectional power flows for different PV penetration levels. Using the net bus load model, three extreme bifurcation points on voltage stability limit hypersurface are formulated where two of these points represent the voltage stability bifurcation interval in the forecasted net bus loading direction. An iterative method is applied to obtain bifurcation solutions. The validity of the proposed method is verified by using the IEEE 3-bus system, the IEEE 33-bus system and the IEEE 123-node test feeder. The numerical results demonstrate that the proposed sandglass-hyper-ellipsoid-cone net bus load model and solutions are effective in managing correlated net bus load forecast errors in distribution systems with PV integration.

Stability analysis in the power system is becoming more important than ever as more distributed energy resources penetrate in the system. This study presents a novel load pattern voltage stability index (LPVSI) applicable to transmission and distribution systems. By considering the nominal value of voltages, the power network is converted into a two-bus equivalent system. Then, LPVSI is derived by only the real-time measurement of the voltage and deviation of active and reactive power loads. Also, the assessment of distributed generation's penetration level on unbalanced systems, with maximum loadability and power loss reduction constraints, is performed with regard to daily load variations. The accuracy and efficiency of the proposed indicator are tested on an unbalanced 34-node radial distribution system. Obtained results in comparison with some other papers in the literature demonstrate that the proposed voltage stability index is fast and effective in identifying non-trivial instabilities in the power system networks.

This study proposes a robust optimisation method for controller parameter tuning of Static Synchronous Compensators (STATCOMs) to enhance the stability of a wind-penetrated power system. The uncertainties of the wind power output and the pre-contingency state of STATCOMs, which both have a significant impact on the solutions, are addressed. Firstly, a novel index is proposed to quantify the robust optimality of the solutions, which is the sensitivity of solution results to the variations of the potential uncertainties. Then, a multi-objective robust optimisation model is proposed to simultaneously optimise three objectives: (i) short-term voltage stability index, (ii) transient (rotor angle) stability index, and (iii) robustness of the solutions. Finally, an improved non-dominated sorting genetic algorithm-II is developed with (1) Latin hypercube sampling-based initial generation, and (2) adaptive mutation rate. The proposed method is tested on a modified New England 39-bus system with industry-standard models and recommended model parameters. Simulation results verify that the much higher computational efficiency and the stronger robustness of the proposed method over conventional methods.

This paper proposes an effect orientated approach to enhance the short-term voltage stability for wind-penetrated power systems. The low system stability with high uncertain renewable energy is addressed by coordination of network and non-network solutions, i.e., STATCOM placement and UVLS respectively in this paper. The proposed model considers the uncertainties of power systems, including operating points load dynamics and multiple contingencies. Unlike other methods that try to minimize the cost, the proposed method aims to maximize the voltage stability enhancement with a fixed cost. The high computing burden is alleviated by a net flow-based scenario reduction algorithm. Compared with the conventional approaches, this paper has three major contributions: 1) Device placement is coordinated with demand response. 2) Operating points and type 4 wind turbines are considered. 3) An effect maximizing DP algorithm with a robust scenario reduction method is applied. The effectiveness and efficiency of the proposed method is demonstrated on the New England 39-bus test system.

The penetration of power electronic interfaced generation (PEIG) is expected to reach up to 65% in some parts of the European power system by 2030 (at least during some hours of the year). Under such grid conditions, system security challenges are observed with frequency stability, voltage stability and undamped converter control interactions being among the most important issues. This study presents a short-term voltage stability assessment of the Great Britain synchronous area under EMT modelling assumptions. The study provides a mapping of system stability and identifies the critical penetration level of PEIG that instabilities are observed. In addition, an application of a grid forming control scheme (namely the enhanced direct power control) is proposed as a mitigation option which is applied here on full-converter interfaced wind power plants (type-4). The simulation results reveal that the application of the grid forming control to a part of the total wind power generation fleet can mitigate the instabilities observed, while enabling the system operation with 100% PEIG.

Voltage instability is considered as one of the main threats to secure operation of power system networks around the world. Nowadays, Integration of large-scale wind power may have severe impacts on the power system operation. Stable, reliable and economic operation of the power system under the massive integration of wind power is a big challenge to power system operators. This paper scrutinizes to study the voltage stability problems for the integration of wind power to the IEEE-39 bus-systems. The main objective of this study is to analyze the voltage stability of the IEEE-39 bus networks with large-scale wind power under normal operation using PV and QV analyses. As one of the classic static Voltage stability assessment (VSA) method, the P-V curve is widely used in identifying the weak buses in one power system. Normally, there is a required range of bus voltage variation that restricts load with fixed power factor within a maximum value. The loading margin can be defined as the distance between the operating point and the maximum load. These steady-state methods, which inherently require less computational capability, can indicate the level of stability of a power system. Therefore, QV curves analysis tools are used in this paper. The importance of accurate representation of the reactive power capabilities of wind generators in voltage stability studies was emphasized in the analyses. These analyses define the amount of reactive power required to enhance voltage stability and hence can be improved by adding suitable reactive power compensator. Here STATCOM is used as a reactive power compensator. Simulation of the 39 bus-IEEE network with integrated wind generators are developed using PSS/E software. يعد أتزان الجهد واحدة من أهم المتحديات لأنظمة الطاقة حول العالم.يعتبر التوسع في ربط محطات الرياح له تأثير بالغ علي أنظمة الطاقة. فطتحديات أنظمة الطاقة تتمثل في الثبات والاعتمادية والتشغيل الاقتصادي للشبکة الکهربائية. وهذا البحث العلمي قائم علي دراسة استقرار الجهد لأنظمة الطاقة مع وجود العديد من مشاريع الرياح المرتبطة بالشبکة الکهربائية. وقد تم اختيار شبکة مکونة من ٣٩ بارة لتمثل حالة الدراسة. ومن أهم أهداف هذه الدراسة هو دراسة وتحليل وضع الجهد الکهربائي للشبکة المشار إليها مع وجود العديد من محطات طاقة الرياح بنسب انتشار مختلفة وذلک في وضع التشغيل العادي باستخدام برنامج تحليلى الجهد والقدرة الفعالة وتحليل الجهد والقدرة الغير فعالة وذلک باستخدام برنامج محاکاة نظام الطاقة للهندسة. ويعد تحليل الجهد والقدرة الفعالة أحد العوامل لتقييم وضع الجهد الکهربائي للشبکة بين وضع التشغيل العادي وأقصي تحميل ممکن للشبکة حيث أن للجهد الکهربي سماحية يتغير في حدودها مع الحفاظ علي استقرار الشبکة. أما تحليل الجهد والقدرة غير الفعالة فهو مقياس لقدرة البارات الغير فعالة وتأثيرها المباشر علي الجهد الکهربائي وبيان نقاط الضعف في الشبکة حيث عدم توافر ما يکفي من القدرة غير الفعالة وما يترتب عليه من إمکانية إضافة محسنات جهد لتلک النقاط کما هو موضح في هذه الدراسة.

En la actualidad el posicionamiento de los sistemas de Generación Distribuida (GD) y Microrredes Eléctricas (MREs) han tomado connotadas participaciones alrededor del mundo. Por lo tanto, las necesidades investigativas en torno al control, operación, estabilidad y resiliencia de estos sistemas han marcado un nuevo paradigma de los sistemas de suministro de energía eléctrica. El objetivo de este artículo es mejorar la estabilidad de tensión mediante la inclusión de un dispositivo DSTATCOM de tecnología FACTS en una MRE integrada por GD de tipo Solar Fotovoltaica y Convencional. La metodología desarrollada se aplica en el sistema de prueba de MRE de la CIGRÉ, con la premisa de analizar dos escenarios operativos en relación a la ocurrencia de una contingencia, con lo cual la MRE operará en forma aislada. El análisis se realiza a través de simulaciones dinámicas en el domino del tiempo, donde se analiza y evalúa el comportamiento dinámico de la tensión, después de que los sistemas red-MRE han sido sometidos a perturbaciones, desencadenando la operación en isla eléctrica de la MRE. Los resultados muestran que los modelos y algoritmos de control desarrollados operan satisfactoriamente, además se demuestra la aplicabilidad y beneficios en la instalación de dispositivos FACTS tipo DSTATCOM en sistemas de MREs para mejorar las condiciones operativas en especialmente en términos de estabilidad de tensión.

Increasing renewable energy sources in power system has brought forth many challenges in terms of power system stability, one of which is voltage stability. Preventive and corrective actions to alleviate voltage instability are mainly developed for traditional power systems without high share of renewables. This article aims to assess the reactive power based voltage support from wind power plants under stressed voltage conditions. Firstly, the performances of the conventional wind power plant control strategies applied during stressed voltage conditions are studied. A novel enhanced wind power plant control strategy is developed, which increases wind power plant reactive power capability through control of wind power plant tap changing transformer. Performance of this novel strategy is compared and evaluated against the conventional wind power plant control strategies applied during the stressed voltage conditions. Results show that the developed control strategy helps in alleviating voltage instability 5% more effectively when compared to the conventional WPP control strategies applied during stressed voltage conditions. The developed control strategy is implemented and simulated in a snapshot of the Hellenic power system to verify the implementation feasibility and effectiveness in a real large power system.

Microgrids (MGs) have been widely implemented as they increase the efficiency and resiliency of electrical networks. However, the uncertain nature of renewable energy resources (RERs) integrated into the MGs usually results in different technical problems. System stability, the most challenging problem, can be achieved via a robust power management strategy (PMS) of the MG. This paper introduces a PMS based on adaptive neuro fuzzy inference system (ANFIS) for AC MG consisting of a diesel generator (DG), a double fed induction generator (DFIG) driven by a wind turbine (WT) and a solar photovoltaic (PV) panel. The proposed strategy aims to achieve MG power balance, decrease DG fossil fuel to minimum consumption, keep the MG voltage stability and finally tracking the maximum power point (MPP) of each RER. Metaheuristic optimization techniques; including genetic algorithm (GA) and particle swarm optimization (PSO), are employed to train the ANFIS to accomplish the desired objectives and fulfill the generation/consumption balance. The proposed AC MG with the PMS is simulated by the MATLAB/Simulink software in order to analyze the system performance under different climatic conditions. The simulation results under symmetrical and asymmetrical electrical faults validated the effectiveness of the proposed strategy.

Real-time voltage stability assessment (VSA) has long been an extensively research topic. In recent years, rapidly mounting deep learning methods have pushed online VSA to a new height that large amounts of learning algorithms are applied for VSA from the perspective of measurement data. Deep learning methods generally require a large dataset which contains measurements in both secure and insecure states, or even unstable state. However, in practice, the data of insecure or unstable state is very rare, as the power system should be guaranteed to operate far away from voltage collapse. Under this circumstance, this paper proposes an autoencoder based method which merely needs data of secure state to evaluate voltage stability of a power system. The principle of this method is that an autoencoder purely trained by secure data is expected to only create precise reconstruction for secure data, while it fails to rebuild data of insecure states. Thus, the residual of reconstruction is effective in indicating VSA. Besides, to develop a more accurate and robust algorithm, long short-term memory (LSTM) networks combined with fully-connected (FC) layers are used to build the autoencoder, and a moving strategy is introduced to bias the features of testing data toward the secure feature domain. Numerous experiments and comparison with traditional machine learning algorithms demonstrate the effectiveness and high accuracy of the proposed method.

In order to solve the problem of vulnerability assessment of complex power systems facing complex structures and large sizes, a novel data driven method based on random matrix theory is proposed in this paper. Firstly, with the use of phasor measurement units (PMUs) big data, evaluation matrices are constructed to extract statistical characteristics of power systems operation. Then, with the combination of random matrix theory and entropy theory, vulnerability evaluation index are constructed considering the degree of influence of some faults in power systems. With full use of big data, the model-free method is more accurate and comprehensive. Simulation results in IEEE 39-bus test system and a real-world power grid in China verify the effectiveness of the method.

This article presents a machine learning approach to predict the long-term voltage stability margin as represented by the Loadability Margin (LM). LM is an intuitive and easily understandable indicator of voltage stability. The unique feature of the proposed technique is the use of different Voltage Stability Indices (VSI) proposed in the literature as inputs to an ensemble of machine learning models which predict the LM. The VSIs used are carefully selected to include those based on different principles and computable using real time synchrophasor measurements. In addition, the paper presents a methodology to generate training data under different operational conditions and N-1 contingencies to train the machine learning models. The best machine learning algorithm and the categories of input VSIs are selected through a comparative study. These studies were conducted on the IEEE 14 bus system and IEEE 118 bus system and led to the selection of Random Forest Regression machine learning algorithm, and confirmed the accuracy and robustness of the proposed method. The system was implemented on real time PhasorSmart® synchrophasor application platform and validated using RTDS® real-time simulator. The impact of synchrophasor measurement errors on the proposed technique were also analyzed.

This paper presents a new method for voltage analysis for islanded microgrids using the energy function method and a new technique based on an auxiliary function to allocate intermittent sources. The energy function allows the direct stability evaluation of the system operating points, taking into account the variation of loads, the intermittence of the photovoltaic, and the charging/discharging of energy storage systems under pre-defined conditions. The auxiliary function is applied as a planning tool, defining the weak system areas, where photovoltaics and energy storage systems can be allocated. The results show the voltage stability assessment’s effectiveness using the energy function and the improvement of the system stability condition when allocating the intermittent sources in the microgrid area indicated by the auxiliary function technique.

The implementation of distributed generation (DG) becomes more common while causing a challenge to maintain the voltage stability in a power system. The optimal placement of multiple DGs in a planning stage can effectively solve this problem. In many cases, the best placement has been determined by the small-signal study like the modal analysis. However, it is acceptable only if the linearization of large-scale nonlinear power system is accurate. To overcome this, this paper proposes the new optimal placement algorithm for multiple DGs based on the model-free Lyapunov exponent estimation to maintain the voltage of system stable. In other words, the individual Lyapunov exponents of all buses are firstly estimated to determine the candidates for optimal placement of DGs. Then, the maximum Lyapunov exponent for each candidate is calculated to decide which bus is the best place to improve the voltage stability of system. Several time-domain simulation studies are carried out to verify the effectiveness of proposed algorithm. In particular, its performance is compared with that of the conventional method. The results show that the optimal placement of multiple DGs determined by the proposed algorithm improves the voltage stability of system much more effectively.

Electrification of the transportation is taking place at an accelerated rate. Even though, electric vehicles (EV) evidently bring numerous environmental and economic benefits, their impact on power systems should not be overlooked. It has been identified that EV load characteristics can significantly affect power system voltage stability and small signal stability. Hence, it is important to consider mitigating of stability impacts right from the planning stage of bulk EV charging stations. However, unavailability of suitable stability evaluating indexes that could fit into planning algorithms is a hindrance. This study proposes two computationally efficient indexes to compare stability status in different planning options. The developed indexes have been tested, verified and utilized in a multi objective planning algorithm to identify a comprehensive solution, which satisfies the grid operator, EV customer and the charging facility investor optimally.

This paper studies energy consumption management of seawater Reverse Osmosis (RO) desalination plants to maintain and enhance the Voltage Stability (VS) of Power Systems (PS) with Photovoltaic (PV) plant integration. We proposed a voltage-based management algorithm to determine the maximum power consumption for RO plants. The algorithm uses power flow study to determine the RO plant power consumption allowed within the voltage-permissible limits, considering the RO process constraints in order to maintain the desired fresh water supply. Three cases were studied for the proposed RO plant: typical operation with constant power consumption, controlled operation using ON/OFF scheduling of the High-Pressure Pumps (HPPs) and controlled operation using Variable Frequency Drive (VFD) control. A modified IEEE 30-bus system with a variable load was used as a case study with integration of three PV plants of 75 MWp total power capacity. The adopted 33.33 MW RO plant has a maximum capacity of 200,000 m3/day of fresh water production. The results reveal that while typical operation of RO plants can lead to voltage violation, applying the proposed load management algorithm can maintain the vs. of the PS. The total transmission power loss and power lines loading were also reduced. However, the study shows that applying VFD control is better than using ON/OFF control because the latter involves frequent starting up/shutting down the RO trains, which consequently requires flushing and cleaning procedures. Moreover, the specific energy consumption (SEC) and RO plant recover ratio decreases proportionally to the VFD output. Furthermore, the power consumption of the RO plant was optimized using the PSO technique to avoid unnecessary restriction of RO plant operation and water shortage likelihood.

Considering the strong influence of distributed generation (DG) in electric distribution systems and its impact on network voltage losses and stability, a new challenge has appeared for such systems. In this study, a novel analytical algorithm is proposed to distinguish the optimal location and size of DGs in radial distribution networks based on a new combined index (CI) to reduce active power losses and improve system voltage profiles. To obtain the CI, active power losses and voltage stability indexes were used in the proposed approach. The CI index with sensitivity analysis was effective in decreasing power losses and improving voltage stability. Optimal DG size was determined based on a search algorithm to reduce active power losses. The considered scheme was examined through IEEE 12-bus and 33-bus radial distribution test systems (RDTS), and the obtained results were compared and validated in comparison with other available methods. The results and analysis verified the effectiveness of the proposed algorithm in reducing power losses and improving the distribution system voltage profiles by determining the appropriate location and optimal DG size. In IEEE 12 and 33 bus networks, the minimum voltage increased from 0.9434 p.u and 0.9039 p.u to 0.9907 p.u and 0.9402 p.u, respectively. Additionally, the annual cost of energy losses decreased by 78.23% and 64.37%, respectively.

In order to meet the growth in demand and the renewable energy integration target, the Sulawesi Electricity System (SES) should be expanded. Currently, the SES is divided into two systems, namely South and North Sulawesi. These two systems have different characteristics, such as the system size, reliability and operational cost. North Sulawesi is smaller, weaker and more expensive than the South System. In order to improve the system reliability, generation and transmission expansion planning should be executed simultaneously to meet the economical investment cost and satisfy the reliability standard. For this purpose, the necessity of a backbone system with a higher voltage level than the existing 150 kV system should be considered, including the interconnection option between the two existing systems in Sulawesi. A methodology based on economic and technical criteria was developed to determine the backbone voltage level. Two voltage level options were considered, namely 275 and 500 kV. Several criteria were considered in order to determine the backbone voltage level, including the economic voltage, the line-loading limit, N-1 contingency, short circuiting, transient stability, voltage stability and small signal stability. The backbone voltage candidates should fulfil all of the criteria. The simulation was conducted in base- and high-demand scenarios, considering the fluctuation of future economic growth. The load flow and the dynamic analysis were simulated in a DIgSILENT Power Factory environment. The results showed that the 275 kV backbone, which was built in 2022, would violate three criteria: the economic voltage, N-1 contingency and voltage stability. On the other hand, the 500 kV backbone voltage level fulfills all of the criteria. The result of this research was considered in the electricity planning documents in Sulawesi. From a technical and economical perspective, the 500 kV backbone was chosen for the SES.

The paper studies the influence of the hybrid renewable energy source (HRES) plant on system voltage stability. System stability analysis is carried out for a set of the most probable annual HRES plant compositions. These compositions are obtained from the historical HRES plant production data set using an unsupervised clustering method. Identification of patterns in the results of voltage stability studies enables the development of equivalent models (EMs) of the whole plant. The EMs are derived in the form of a synchronous machine with adequate reactive power support capability and connected to the grid at the same bus as the HRES plant. The results obtained with the test system have shown that a few EMs are sufficient to represent the whole HRES plant in voltage stability studies throughout the year.

Power system voltage instability is major threats to reliable operation of power system networks. Nowadays maintaining a stable power system is therefore a challenging issue. If we consider economic and environmental concerns, grid tied renewable energy-based generation are growing over the past few years. These kind of generation can have both advantages and disadvantages. The most commonly used renewable energy resource is solar photovoltaic. This paper mainly focuses on voltage stability analysis of power network when penetrated with solar photovoltaic (PV). For the investigation, a comprehensive model of solar PV penetration in IEEE-14 bus test system has been used. Load flow study has been performed to analyse the voltage stability of the system. Critical eigenvalues of Q-V modal matrix is used to examine the effect of PV generator on voltage stability of power system. The effects of scattered and concentrated PV penetration on power network are also analyzed in this paper.

This paper proposes a rapid analytical method to determine the locations and sizes of multiple distributed generations (DGs) inside a distribution network. DGs locations are chosen with the aim of enhancing voltage stability and their sizes are picked so as to minimize system power losses. To evaluate the effect of the DG's nature on the system's performance, the proposed DG allocation method is tested for all DG types and the impact of the combination of different types of DGs is equally investigated, which offers a guide to designing an optimal hybrid network.