Linear and nonlinear methods for contingency analysis in on-line voltage security assessments (original) (raw)

Contingency evaluation for voltage security assessment of power systems

2009

The demand for electricity is expected to continue to increase given the recent world population projection of about 30% increase in the next three decades. Consequently power systems are equally expected to be more heavily loaded than before. Unfortunately the environmental and economic constraints restrict the expansion of the existing power system facilities. This scenario requires a constant attention since it could result to voltage collapse which could in turn lead to a total blackout. This paper presents the procedure required to carry out a contingency assessment and ranking of the load buses and lines of power systems for voltage security. This would ensure that power systems are operated above a desired voltage stability margin to forestall voltage collapse. The impact of single line outage contingency on the static voltage stability margin, as well as the available transfer capability across the areas of the test system, are examined in the paper.

An advanced tool for preventive voltage security assessment

2000

Summary. This paper deals with methods for the preventive assessment of voltage security with respect to contingencies. We describe a computing tool for the determination of secure operation limits, together with methods for contingency filtering. Examples from two very different real-life systems are provided. We outline extensions in the field of preventive control. ... Keywords. Voltage security assessment, contingency analysis, contingency filtering, preventive control ... In the recent past, a significant number of incidents throughout the world have resulted in ...

An efficient approach for contingency ranking based on voltage stability

International Journal of Electrical Power & Energy Systems, 2004

This paper presents an efficient approach for line outage contingency ranking based on voltage stability concerns. This is achieved through non-iterative fast calculation of reactive support and voltage security indices using Norton's equivalent. Earlier approach required full AC load flow for every contingency simulation. Results for IEEE, 30 bus, 57 bus and an Indian 91 Bus Power Systems have been obtained to demonstrate the effectiveness of the algorithm.

Contingency Selection in the Context of Voltage Security Margin Determination

ICICCT 2019 – System Reliability, Quality Control, Safety, Maintenance and Management, 2019

The present day power utilities highly stressed and operate very close to the stability limit. Because of this, the power utilities are confronting the issue in keeping up the required bus voltages. The power system which happened to be limited by transient (angle) stability have now moved toward becoming voltage stability constrained. Henceforth, the focal point of this paper is being on voltage stability and voltage security analysis. The voltage security can be assessed by performing AC load flow for different outages. Practically in a Power System, number of contingencies is large to the point that they can't be investigated online by the AC load flow strategies. Subsequently the contingencies are, firstly, ranked according their relative degree of severity by implementing suitable selection algorithms. After this, the more severe contingencies are selected for full AC load flow analysis. This paper presents a functional link model based Artificial Neural Network (ANN) for the prediction of post-outage bus voltages. The contingencies are, then, ranked by implementing fuzzy logic approach by considering voltage deviation and voltage stability margin as well.

A Simple Contingency Selection for Voltage Stability Analysis

Electronics and Electrical Engineering, 2013

The paper deals with a selection of potentially critical contingencies from the voltage stability viewpoint. Consideration of all contingencies is impractical. Before contingency analysis starts, one can state, that certain contingencies need not be taken into account. In the paper, after a short overview of the existing papers, in which the problem of the selection of contingencies is considered, the new method for selection of contingencies is presented. A selection of contingencies is based on results of testing of possible power transfers in a power network after the contingencies occur. During the tests, assessments of extreme values of active and reactive power flows, which change when power system state changes, are taken into consideration. In the paper, a computational example of utilization of the described method is given. At the end, the most important features of the method are pointed out.

Application of Real-Time Voltage Security Assessment to the Hellenic Interconnected System

This paper describes the on-line Voltage Security Assessment methods implemented at the national control center of the Hellenic Interconnected System, within the framework of the OMASES project funded by the European Union. The heart of all computations is a fast time-domain method. Security is analysed with respect to power transfers in critical corridors or power consumption in load areas. Results take on the form of either pre-contingency secure operation limits, or post-contingency loadability limits, together with various diagnosis tips. Contingency filtering is performed to meet the real-time requirement. Typical results obtained during the test phase of the project are reported.

Online Voltage Security Assessment in the Hellenic Interconnected System

Savulescu/Real-Time Stability Assessment, 2008

This paper describes the on-line Voltage Security Assessment environment developed within the framework of the EU-sponsored OMASES project, as well as its application to the Greek Interconnected Power System. The heart of all computations is a fast time-domain method. Security is analyzed with respect to power transfers in critical corridors or power consumption in load areas. Results take on the form of either precontingency secure operation limits, or post-contingency loadability limits, together with various diagnosis tips. Typical results obtained during the test phase of the project are reported.

Artificial neural network model for voltage security based contingency ranking

Applied Soft Computing, 2007

The continual increase in demand for electrical energy and the tendency towards maximizing economic benefits in power transmission system has made real-time voltage security analysis an important issue in the operation of power system. The most important task in real time security analysis is the problem of identifying the critical contingencies from a large list of credible contingencies and rank them according to their severity. This paper presents an artificial neural network (ANN)-based approach for contingency ranking. A set of feed forward neural networks are developed to estimate the voltage stability level at different load conditions for the selected contingencies. Maximum L-index of the load buses in the system is taken as the indicator of voltage instability. A mutual information-based method is proposed to select the input features of the neural network. The effectiveness of the proposed method has been demonstrated through contingency ranking in IEEE 30-bus system. The performance of the developed model is compared with the unified neural network trained with the full feature set. Simulation results show that the proposed method takes less time for training and has good generalization abilities. #

An adaptive correction for voltage security analysis using a local approach solution

IEEE Transactions on Power Systems, 1994

This paper presents an efficient contingency screening for voltage limit violations. The screening process is based on the local approach solution. A separation in the Q-mismatch calculations between buses situated in the vicinity of the perturbation and buses electrically far away from the perturbation is used. This approach takes advantage of the fast convergence rate of buses that are far from the outaged equipment [l] and allows fast and accurate Q-mismatch calculations. The concept of electrical distance is also used in order to predict the buses in which major voltage shifts can occur after the contingency. The solution usually corresponds to the single iteration of the well known Fast Decoupled Load Flow [ 6 1 model on which an adequate correction is applied in order to detect all possible contingencies that can cause limit' violations. This solution can also be carried out with two iterations instead of the traditional one iteration scan methods. Results of tests with a 206 bus-299 branch 400 kV French network show that CPU time required for two partial iteration scans is almost equivalent to one complete iteration (1P-lQ) of the Fast Decoupled Load Flow model. In fact, computation time is saved by using approximate Q-mismatch calculations, by setting small Q-mismatches at zero and by using sparse vector techniques for non zero mismatches (Fast Forward, Fast Back solutions). The number of buses involved f o r the solution process is drastically reduced especially for the second iteration and accuracy is better than with traditional methods.

Power system simulation and contingency ranking using load bus voltage index

2014

Given the importance of the power system security and the role of the operator in enhancing this feature, improving the operator's actions and information in the power system management is critical. The proper tools and available information for the operator can continuously improve the power system security. During power system operation, the operator needs to identify probable hazardous contingencies to assess power network security online. Thus, contingency ranking based on their importance has always been of interest to researchers. In present study, a new method is proposed for appropriate contingency ranking and online power network security assessment based on the Phasor Measurement unit (PMU) data. In the proposed method, unlike the previous methods, two voltage and angle indices were used. Since the variables of load-flow studies are used to calculate the proposed index, this index can provide a comprehensive assessment of the network security. The proposed index is implemented on three IEEE 14-, 30-and 57-bus test systems to evaluate its performance. First, using this index, contingency analysis is carried out in 2000 operational points and the obtained results are compared with a randomly selected operating point. The results indicated the performance and response time of the proposed index.