Contingency Ranking Research Articles

Ensuring grid resilience: Voltage stability analysis and contingency ranking in electric power systems

Modern-day power systems are highly stressed and operate close to the stability limit. The bus voltage variation in power systems generally infringes on the researcher's mind about voltage stability. The main focus of this manuscript is the voltage stability problem and voltage security assessment rather than the angle stability problem. Voltage security can be determined by running a full-load AC load flow with contingency analysis. In real-time analysis, running thousands of contingencies in online mode is quite a cumbersome task, so here in this manuscript, we have proposed a functional link-based ANN for voltage security assessment and then predicted the weakest voltage control area by the entropy concept along with the placement of FACTS devices according to the voltage control area weakness factor and contingencies ranking. The novel technique is then tested with IEEE-14 Bus and IEEE-30 Bus systems with voltage stability performance indicators.

Voltage stability assessment and contingency ranking in power systems based on modern stability assessment index

Electric loads steadily increase each year due to economic and population expansion, placing electric systems close to their stability limits. Also, the electrical network is a sophisticated system with various control, protection devices, and power electronics. Any malfunction in these components can disrupt system reliability. Therefore, ensuring safe and dependable power system operation requires continuous and precise voltage stability monitoring to prevent instability and cascading outages. Despite the existence of numerous stability indexes, their limitations often make them ineffective under varying operating conditions. In response to these challenges, this article proposes a modern stability assessment index (MSAI) designed specifically to assess voltage stability in different operating scenarios. The MSAI aims to accurately assess voltage stability and stress levels in power lines, enabling operators to proactively manage system reliability. One key advantage of the MSAI is its ability to determine the maximum allowable load and loading margin, which is crucial for maintaining stable operation under changing load conditions. In order to validate the effectiveness of the proposed index, extensive evaluations are conducted using IEEE 30, 57, and 118 bus test systems. The study meticulously compares the performance of the MSAI with other prominent stability indicators, highlighting its superiority in providing predictive insights into areas prone to stress and potential contingencies. By empowering operators with preemptive correction capabilities, the MSAI reduces the risk of successive outages and enhances overall system flexibility. The voltage stability assessment and contingency ranking were evaluated using the proposed MSAI via a smooth method in the MATLAB environment.

AC–DC security-constrained optimal power flow for the Australian National Electricity Market

This paper presents a new methodology to solve the integrated ac–dc security-constrained optimal power flow (SCOPF) problem for large-scale power systems, with a focus on the Australian National Electricity Market (NEM). The proposed SCOPF is based on a decomposition scheme that significantly reduces the dimensionality of the problem and thus improves the computational performance. It further supports a contingency ranking, evaluation, and non-dominated filtering algorithm, cyclic selection of filtered contingencies, careful choice of slack variables, and a tailored warm start to the nonlinear problem. The methodology is validated against the two-stage mathematical programming model that uses an explicit nonlinear model of both the base case and the contingency cases, at a slightly higher cost but significantly faster execution. Moreover, the NEM power system, is studied addressing different scenarios including load variations, renewable energy zone integration, and additional reinforcements like point-to-point and meshed HVDC. The proposed approaches provides preventive solutions in less than 5 min thus affirming the model’s effectiveness in real-time applications and planning studies.

Novel risk index integrating practical operation limits enhances probabilistic contingency ranking for large-scale photovoltaic plant planning

This research addresses the pressing need for heightened grid security amid increasing uncertainties in photovoltaic PV generation. The research problem lies in the limitations of conventional contingency analysis metrics, failing to adequately consider both contingency occurrences and uncertainties inherent in PV generation. In response, a comprehensive algorithm is proposed that introduces a novel severity function framework, enhancing traditional contingency ranking metrics. This approach incorporates grid remedial actions and refines line and bus voltage classification by considering available correction time, aiming to offer a more robust security assessment. Motivated by the imperative to address uncertainty in PV generation, the proposed work builds on established analysis tools. A probabilistic load flow algorithm manages PV generation uncertainties, utilizing historical data for contingency incidence uncertainty. Additionally, a probabilistic model for PV plants integrates historical solar data, deriving hourly probability density functions to meet grid code requirements, including reactive power considerations. The justification for this work lies in the algorithm's demonstrated efficacy, validated on the IEEE 14-bus network. Results highlight its ability to identify risks associated with line overloading and bus voltage breaches. Comparative evaluations underscore proper coupling buses for security, favoring distributed capacity to mitigate line overloading risks. The study's key results emphasize voltage risk amplification with reactive power omission, stressing the significance of compensation strategies. This research addresses a critical problem, presenting a comprehensive algorithmic solution to enhance grid security amidst uncertainties in PV integration. Findings offer valuable insights for strategically interaction between large scale PV plants and electrical grid, contributing to an improved grid security paradigm in a dynamic and uncertain energy model.

Voltage stability improvement and power losses reduction through multiple grid contingency supports

A stable power system is a desirable state for the optimal performance and delivery of electricity to the end-users. This study evaluates the effectiveness of grid contingency support devices in power system stability enhancement. The new voltage stability pointer (NVSP) was employed to optimally infer the flexible alternating current transmission systems devices through N − 1 contingency ranking. In this research, the static synchronous compensator (STATCOM) was considered as a grid support device. The effectiveness of this technique was validated in R2018a MATLAB with the IEEE 30-bus system using different combinable contingency cases to ascertain the critical lines and vulnerable buses to outages. Based on the results obtained through the NVSP, buses 30, 26, and 29 were cited as STATCOM candidate buses for overall optimal grid performance. The results obtained from the simulation revealed that the total real power loss was reduced by 90.21%. Similarly, the voltage magnitude of the buses was significantly improved to a minimum of 1.00 p.u. after placement of STATCOMs. Further investigation on single STATCOM placement in the IEEE 30-bus system revealed that the highest level of voltage improvement, minimum level of voltage deviation and maximum active power loss reduction was achieved when the STATCOM was placed at bus 30. The overall assessment of the proposed technique yielded better results compared with other methods on the same test system.

Evaluation and Improvement of Power System Security with the Application of Machine Learning

The electricity grid has added many renewable and non-renewable energy sources to meet expanding demand. Sudden load variations exacerbate generator, transmission line, and distribution network issues. Load modelling choices are crucial for system prediction. This study indicates that ZIP load models with contingency criteria can accurately forecast load behaviour over time. The NR method predicts the contingency ranking with the High Bride Line Stability Ranking Index (HLSRI) under single line outage conditions, and an artificial neural network (ANN) is trained to predict the severity of the line outage and the system's behaviour. A mathematical model was utilised to analyse stability and cost with and without the UPFC and IPFC. Machine learning (ML) is used to rapidly predict the most affected transmission line during a contingency by clustering data using the J48 algorithm for the location of compensating devices. The PSO algorithm is used to develop an objective function to minimise fuel costs by maximising generating capacity. A transmission line failure and load variation might damage the electrical system. This study prioritises transmission line breakdowns and load changes. Power system security analysis provides power system status.

High-performance computing for static security assessment of large power systems

Contingency analysis (CA) is one of the essential tools for the optimal design and security assessment of a reliable power system. However, its computational requirements rise with the growth of distributed generations in the interconnected power system. As CA is a complex and computationally intensive problem, it requires a fast and accurate calculation to ensure the secure operation. Therefore, efficient mathematical modelling and parallel programming are key to efficient static security analysis. This paper proposes a parallel algorithm for static CA that uses both central processing units (CPUs) and graphical processing units (GPUs). To enhance the accuracy, AC load flow is used, and parallel computation of load flow is done simultaneously, with efficient screening and ranking of the critical contingencies. We perform extensive experiments to evaluate the efficacy of the proposed algorithm. As a result, we establish that the proposed parallel algorithm with high-performance computing (HPC) computing is much faster than the traditional algorithms. Furthermore, the HPC experiments were conducted using the national supercomputing facility, which demonstrates the proposed algorithm in the context of N−1 and N−2 static CA with immense power systems, such as the Indian northern regional power grid (NRPG) 246-bus and the polish 2383-bus networks.

A Comprehensive Review on the Modelling and Significance of Stability Indices in Power System Instability Problems

Many technological advancements in the modern era have made actual use of electrical power and the constrained operating of power systems within stability limits. Some expeditious load variations and rising power demands initiate complications in voltage stability and can put stress on performance, leading to voltage instability. Voltage Stability Indices can be used to perform voltage stability assessment. This review evaluates various VSIs based on mathematical derivations, assumptions, critical values, and methodology. VSIs determine the maximum loadability, voltage collapse proximity, stability margin, weak areas, and contingency ranking. Stability indices can also specify the optimal placing and sizing of Distributed Generators. Thus, VSIs play a vital role in power system voltage stability. This review is a comprehensive survey of various indices and analyses their accuracy in determining the instability of power systems. Voltage stability is a crucial concern in operating a reliable power system, and the systematic evaluation of voltage stability is essential in a power system. This review considered and analyzed 34 indices from 138 articles from the literature for their significant performance in various power system stability problems. Of 33 indices, were 22 derived from transmission line parameters, referred to as line indices, and 12 from bus and line parameters, referred to as bus indices.

A Lyapunov spectrum based hybrid static and dynamic approach for contingency ranking

AbstractThe goal of contingency ranking is to provide a list of possible critical situations and rank them according to the severity of their impact on a power network. The methods of contingency ranking may be divided into two major categories: static and dynamic techniques. Static approaches are fast and can be implemented in real‐time, but they present different results depending on the parameter which has been selected for contingency ranking. Dynamic methodologies are more accurate than static ones, but they are time‐consuming. This paper presents a novel combined static and dynamic method for contingency ranking which takes advantage of both techniques and shows the performance evaluation for the hybrid method using accuracy and efficiency as criteria. The proposed method uses three well‐known static indices and the Lyapunov spectrum based dynamic approach to select the worst critical lines. IEEE 39‐bus (New England grid) and IEEE 118‐bus networks are utilized to verify the proposed method. The method provides speed and accuracy. One of the prominent features of the proposed approach is its ability to rank contingencies that lead to network load flow divergence.

Enhancing power system security using soft computing and machine learning

Purpose. To guarantee proper operation of the system, the suggested method infers the loss of a single transmission line in order to calculate a contingency rating. Methods. The proposed mathematical model with the machine learning with particle swarm optimization algorithm has been used to observe the stability analysis with and without the unified power flow controller and interline power flow controller, as well as the associated costs. This allows for rapid prediction of the most affected transmission line and the location for compensation. Results. Many contingency conditions, such as the failure of a single transmission line and change in the load, are built into the power system. The single transmission line outage and load fluctuation used to determine the contingency ranking are the primary emphasis of this work. Practical value. In order to set up a safe transmission power system, the suggested stability analysis has been quite helpful.

Contingency ranking method for voltage security assessment based on critical eigenvalue trajectory

In voltage security assessment it is of great importance to determine the most critical contingencies of the system. However, most of the contingency ranking methods fail to capture the nonlinear behavior of the system, which is more pronounced in the proximity of the system to the voltage collapse point. This paper proposes a contingency ranking method that considers the trajectory of the critical eigenvalue of the jacobian matrix of the power flow equations when the load grows as an indicator of the closeness of the power system to the voltage collapse point. The proposed critical eigenvalue trajectory (CET)-based method utilizes a linear extrapolation of the eigenvalue trajectory. Therefore, for each analyzed contingency, two equilibrium points are obtained and associated with their respective critical eigenvalue, which leads to a linear extrapolation of each critical eigenvalue trajectory. The contingency ranking method is applied on the IEEE 57-bus test system. The results analysis show a good accuracy of the method, specially for the most critical cases. Besides the performance analysis, CET-based method presents good results when compared to the results of two other ranking methods, implemented according to the literature and tested on the same test system.

A Decomposition Algorithm with Fast Identification of Critical Contingencies for Large-Scale Security-Constrained AC-OPF

The article “A Decomposition Algorithm with Fast Identification of Critical Contingencies for Large-Scale Security-Constrained AC-OPF” presents the decomposition algorithm used by Team GO-SNIP for the ARPA-E Grid Optimization (GO) Competition Challenge 1, held from November 2018 through October 2019. The algorithm involves unique contingency ranking and evaluation strategies for determining the important contingencies to include in a master problem that approximates the original large-scale security-constrained problem. It also involves efficient strategies for handling the complementarity constraints that appear in the model and for handling the arising degeneracies. Software implementation details are described, and the results of an extensive set of numerical experiments are provided to illustrate the effectiveness of each of the used techniques. Team GO-SNIP received a second-place finish in Challenge 1 of the Go Competition.

A novel collapse prediction index for voltage stability analysis and contingency ranking in power systems

Voltage instability is a serious phenomenon that can occur in a power system because of critical or stressed conditions. To prevent voltage collapse caused by such instability, accurate voltage collapse prediction is necessary for power system planning and operation. This paper proposes a novel collapse prediction index (NCPI) to assess the voltage stability conditions of the power system and the critical conditions of lines. The effectiveness and applicability of the proposed index are investigated on the IEEE 30-bus and IEEE 118-bus systems and compared with the well-known existing indices (Lmn, FVSI, LQP, NLSI, and VSLI) under several power system operations to validate its practicability and versatility. The study also presents the sensitivity assumptions of existing indices and analyzes their impact on voltage collapse prediction. The application results under intensive case studies prove that the proposed index NCPI adapts to several operating power conditions. The results show the superiority of the proposed index in accurately estimating the maximum load-ability and predicting the critical lines, weak buses, and weak areas in medium and large networks during various power load operations and contingencies. A line interruption or generation unit outage in a power system can also lead to voltage collapse, and this is a contingency in the power system. Line and generation unit outage contingencies are examined to identify the lines and generators that significantly impact system stability in the event of an outage. The contingencies are also ranked to identify the most severe outages that significantly cause voltage collapse because of the outage of line or generator.

Analisis Pengaruh Penambahan Gardu Induk Terhadap Aliran Daya dan Profil Tegangan

Addition of the Guluk-Guluk Substation, it will affect the flow of power and voltage in the electric power system. Based on the analysis of normal conditions before and after the Guluk-Guluk Substation in terms of the voltage value on each connected bus, it is still within the permitted limits, while the contingency ranking calculation using the Voltage Performance Index (PIv) method can determine contingency conditions N-1 to N -3 before and after the Guluk-Guluk Substation. In this case, it was found that during the contingency conditions N-1 to N-3 before the Guluk-Guluk Substation there was a decrease in the value of the voltage which was still within the permissible limits, but in the N-3 contingency there was also an overload on the line due to the release of two generator units and one channel. After the existence of the Guluk-Guluk Substation, during the N-1 to N-2 contingency conditions the voltage value was still within the permissible limits, but the voltage drop that occurred was bigger than the condition before the Guluk-Guluk Substation. For the N-3 contingency condition the voltage value does not meet the standard due to overload on the Ujung Substation - Bangkalan Substation line and the lack of power flow.

Investigations on hybrid line stability ranking index with polynomial load modeling for power system security

Introduction. In recent years, numerous non-renewable and renewable energies are connected to the grid to meet the demand. Also, transient variation with loads poses the shortcomings for generating units, transmission and distribution networks. In this regard, the study on choice of suitable load modelling is essential to predict the system characteristics. The aspect of the research design is a ZIP load model, which, when combined with contingency criteria and constant-impedance, constant-current, and constant-power loads, produces realistic and long-term load representations. Purpose. The proposed technique, infers the single transmission line outage for obtaining the contingency ranking to ensure the system behavior. Methods. The proposed mathematical model with hybrid line stability ranking index has been used for observing the stability analysis with and without considering unified power flow controller. Results. The power system involves many unpredictable conditions or contingency conditions like single transmission line outage, double transmission line outage, generator outage and load variations. This paper mainly focuses on the single transmission line outage for obtaining the contingency ranking. Practical value. The recommended stability analysis has been very beneficial in establishing a secure transmission power system.

Fast contingency screening for voltage stability analysis considering both SNBs and SIBs

Polynomial extrapolation usually leads to crude approximations of the so-called nose curves due to the nonlinear nature of power system operational limits. In particular, these polynomial approximations fail to obtain estimates of the voltage stability margin when the system is subject to structure-induced bifurcations. This paper proposes smoothing out power flow equations to deal with structure-induced bifurcations and verifies the validity of a quadratic approximation of a smooth nose curve in estimating load margin for contingency screening and ranking in voltage stability analysis. Tests of the proposed method in large power systems revealed that an appropriate smooth power flow model can indeed result in better estimates of the exact contingency ranking as compared to the estimates obtained with the original power flow equations. • A smooth formulation of the power flow equations can improve the estimation of VSM. • Both accuracy and speed can be controlled by means of a scalar parameter. • Smoother equations are faster to solve and produce a better contingency ranking.

Analysis of a new voltage stability pointer for line contingency ranking in a power network

Improper management of reactive power in a power network could lead to voltage instability. This paper presents a well-detailed study on voltage instability due to violation of power equilibrium in a power network and introduces a new voltage stability pointer (NVSP). The proposed NVSP is developed from a reduced 2-bus interconnected network to predict the sensistivity of voltage stability to reactive power variation. The simulation results from MATLAB were evaluated on IEEE 14-bus test system. The contingency ranking was achieved by varying the reactive power on the load buses to its maximum loading limit. The maximum reactive power point was taken at each load bus and the critical lines were ranked according to their vulnerability to voltage collapse. The results were compared with other notable voltage stability indices. The results prove that the NVSP is an essential tool in predicting voltage collapse.

When cultural services and biodiversity matter most: Gaining a deeper insight into badlands ecosystem services preferences

AbstractMost dryland ecosystems are characterised by a low ecosystem services (ES) provision, being socially perceived as lacking in cultural and regulating ES. This is the case of the badlands, highly eroded arid ecosystems without vegetation, which have been extensively analysed from a physical point of view, but hardly studied from the point of view of the benefits they provide to society. This paper aimed to determine the social preferences for and the relative importance of the ES provided by badlands. To achieve this objective, a representative sample of the population was taken from the Region of Murcia (Spain), a semiarid Mediterranean area with an abundant presence of these ecosystems. This study area is of additional interest for the provision of ES derived from agroecosystems. The contingent ranking method was used to identify aspects such as the utility provided by the different types of ES and the social well‐being derived from different management policies to be implemented. The results show a preference of the population for cultural ES and biodiversity in the badlands. Given that the implementation of badlands ES protection and a management policy based on the maintenance of agricultural ES are the two strategies that yield the highest social well‐being, the provisioning and regulating ES derived from agroecosystems in the area should be evaluated simultaneously, given the trade‐off that can occur between the two ecosystems. These results provide dryland ecosystem managers with a view of soil erosion management that is different from the traditional one, since it promotes not only its control, but also a greater presence of educational and recreational activities.

Analisis Pengaruh Penambahan Gardu Induk Terhadap Aliran Daya dan Profil Tegangan

Addition of the Guluk-Guluk Substation, it will affect the flow of power and voltage in the electric power system. Based on the analysis of normal conditions before and after the Guluk-Guluk Substation in terms of the voltage value on each connected bus, it is still within the permitted limits, while the contingency ranking calculation using the Voltage Performance Index (PIv) method can determine contingency conditions N-1 to N -3 before and after the Guluk-Guluk Substation. In this case, it was found that during the contingency conditions N-1 to N-3 before the Guluk-Guluk Substation there was a decrease in the value of the voltage which was still within the permissible limits, but in the N-3 contingency there was also an overload on the line due to the release of two generator units and one channel. After the existence of the Guluk-Guluk Substation, during the N-1 to N-2 contingency conditions the voltage value was still within the permissible limits, but the voltage drop that occurred was bigger than the condition before the Guluk-Guluk Substation. For the N-3 contingency condition the voltage value does not meet the standard due to overload on the Ujung Substation - Bangkalan Substation line and the lack of power flow.

Development of agroforestry food resources in Niger: Are farmers’ preferences context specific?

This study deals with key elements for a better understanding of the management approaches of agroforestry systems in Niger. A contingent ranking was conducted to 399 Nigerien farmers in three agroecological zones based on their different socio-economic and environmental conditions. Results show that farmers are willing to improve their natural resources, taking actions to recover and conserve them. Significant differences are found with respect to not only the various agroecological zones where farmers live but also the socio-economic factors of the population. The Tamou municipality prefers to participate in an agri-environmental program based on the conservation of water thorough half-moons technique. Farmers’ preferences in the Maradi region differ from those in the Tillabéri region; the former rely on managed natural regeneration while the latter on tree plantations. Adansonia digitata and Ziziphus mauritiana are the two-priority species to be regenerated by improved seeds. The farmers of Aguié, Madarounfa, and Simiri would be willing to participate in actions scheduled for 9, 6 and 5 months, respectively. Socio-economic factors such as the life strategy of each ethnic group, the role of men and women, the seasonal migration of young people, and the rights to the resources, influence both the period and duration of participation. The results of this study are valuable to design agroforestry policies that involve participation of small-scale farmers, relying on the dynamism of local communities.