Power System Reliability Analysis Research Articles

A comprehensive framework for vulnerability analysis of extraordinary events in power systems

Electric power systems are critical infrastructures subject to the possibility of extraordinary events with high societal consequences. Although such possibilities are often associated with very low probabilities of being realized, it is nevertheless crucial to be able to identify and understand the vulnerabilities of power systems related to extraordinary events. The objective of the work presented in this article is to establish a methodological basis for vulnerability analysis that is complementary to conventional risk and reliability analysis of power systems. It presents a comprehensive framework of definitions, indicators and methods that can be used to classify, analyse and monitor vulnerabilities in power transmission and distribution systems. Its main components include (1) a conceptual framework of definitions that forms the basis for understanding and classifying vulnerabilities, (2) an assessment methodology for identifying vulnerabilities related to extraordinary events and barriers to mitigate them, and (3) vulnerability indicators for quantifying and monitoring power system vulnerabilities. The applicability of the vulnerability analysis framework is demonstrated through several studies of real power systems. Moreover, the concept of power system vulnerability elaborated in this article is also related to the concept of power system resilience.

Reliability and exploitation analysis of ITS power systems including RES

The problem of reliability and exploitation analysis of power systems used in intelligent transport systems (ITS) is extremely important from the point of view of ensuring the traffic safety. The use of advanced electronic devices in ITS systems requires their power supply from properly designed power systems. To ensure the continuity of operation of electronic devices, the basic and backup power supply are most often used. They should have specific values of reliability and performance indicators. Therefore, a reliability and exploitation model of the power system has been developed, taking into account renewable energy sources (RES), such as used in intelligent transport systems. This allowed to obtain dependencies enqabling to determine the probability of staying of the power system used in the intelligent transport system in the specified reliability and exploitation states.

A Novel Generation Rescheduling Algorithm to Improve Power System Reliability With High Renewable Energy Penetration

The uncertainties of renewable energy may bring impacts to power system reliability. This paper proposes a novel generation rescheduling algorithm, which adjusts generation outputs to mitigate the variations of branch power flows and relieve the overload probability. This algorithm helps prevent power congestion and balance the aggregate renewable generations and loads in power systems. Besides, the paper also proposes a probabilistic method evaluating the system uncertainty issue in the power system considering generation rescheduling operation. The proposed generation rescheduling algorithm has been tested on the Arizona transmission system. The generation rescheduling method enhances power system reliability analysis with a high penetration of renewable energy resources.

Composite power system reliability evaluation using modified minimal cut set approach

The composite power system reliability analysis is generally based on minimal path or cut enumeration, tracing of power flow paths from which the related reliability indices are calculated. The minimal cut set is a popular method in the reliability analysis for simple and complex configurations. Average availability of power supply at the consumer end is one of the reliability assessment parameter. This paper is concerned about the evaluation of this reliability index. A step by step procedure for a modified minimal cut set method is explained in this paper using IEEE 6 bus, 14 bus and Single area IEEE RTS 96 system. The proposed algorithm is easy to program and can be applicable to any system. The proposed algorithm is validated with the Classical Node Elimination method, Step by Step algorithm using Conditional Probability and Monte Carlo Simulation method. The proposed technique is tested with a practical example taken from Roy Billinton paper (Reliability evaluation in distribution and transmission systems).

Development of a statistical model for reliability analysis of hybrid off-grid power system (HOPS)

The study presents a response surface (RS) model using Box-Behnken design (BBD) technique for predicting the reliability of a hybrid off-grid power system (HOPS). A three-factor three-level BBD is used to model the reliability of HOPS in terms of loss of power supply probability (LPSP). The sizes of HOPS components, namely, photovoltaic (PV) array, diesel generator (DG) capacity, and battery (BAT) cells, are the factors in the model. The effect of varying PV, DG sizes and BAT cells for the HOPS are thoroughly assessed for minimum LPSP. The analysis of variance (ANOVA) for the response (LPSP) established significant linear and quadratic terms of the RS model. The coefficients of the RS model are determined using multiple regression analysis technique at the 95% level of confidence. The RS model is verified for error in prediction by residual analysis technique and validated against experimental data to confirm the accuracy of the model. The model predicted accuracy is 97.4%. The model predicted optimum HOPS component sizes in terms of LPSP is assessed to define the energy economics of the system. The systematic approach of sizing the power sources of a HOPS in terms of supply reliability using a statistical model and subsequent validation of the prediction with experimental data taking into consideration the cost of energy generated from the system is the unique feature of the present study. The model presented in this study can be a useful tool for comparing power supply reliability of varying capacities among similar system architectures.

Wind Farm Layout Optimization and Its Application to Power System Reliability Analysis

Energy production of a wind farm is greatly affected by the wake-effect. In wind farm planning, it is essential to optimize the layout of wind turbine generators (WTGs) to alleviate the impact of wake-effect. This paper presents a new wind farm layout optimization model with an objective function to maximizing equivalent power of the wind farm. The proposed model incorporates the discrete joint probability distribution and characteristics of the wind, wind energy model, and the wake-effect. A particle swarm optimization algorithm is used to solve the optimization problem. In the optimization process, geometric analysis is conducted to determine the upstream WTGs and to calculate the horizontal and deviating distances among WTGs along the wind direction. An effective look-up table is constructed to directly determine the upstream/downstream WTGs. Then the optimal layout of a wind farm can be obtained. The proposed technique is applied to the wind farm layout optimization and the modified Roy Billinton Test System and IEEE Reliability Test System for reliability analysis of a generating system containing a wind farm. Simulation results demonstrate the validity and flexibility of the proposed technique in the layout optimization of WTGs in a wind farm.

Reliability and sensitivity analysis of composite power systems considering voltage and reactive power constraints

This study investigates the effects of voltage and reactive power constraints on composite system reliability indices. Four indices have been used to assess the sensitivity of load curtailments to voltage and reactive power constraints. Furthermore, expressions to evaluate the sensitivity of the severity indices with respect to the voltage and reactive power constraints have been developed. Extensive simulations on the Institute of Electrical and Electronics Engineers (IEEE) reliability test system based on the AC power flow model were carried out to correlate the violations of these limits and the loading level of the system. A non-linear, AC power flow-based model has been used to accurately represent system redispatch. A state space reduction technique has been utilised to reduce the computation time. A comparison between redispatch models using AC and DC power flow has been provided to illustrate the benefits of the more accurate AC flow model and to investigate the effects of the voltage and reactive power constraints on reliability indices.

Switch Allocation Problems in Power Distribution Systems

Reliability analysis of power systems has been attracting increasing attention. Regulatory agencies establish reliability standards that, if infringed, result in costly fines for the utility suppliers. A special concern pertains to the distribution networks on which most failures occur. The allocation of switches is a possible strategy to improve reliability, by allowing network reconfiguration to isolate contingencies and restore power to dark areas. This paper proposes an optimization methodology to allocate switches on radially operated distribution networks. The solution framework considers sectionalizing and tie switches of different capacities, with manual or automatic operation schemes. The approach minimizes the costs of allocation and energy not supplied, under reliability and flow capacity constraints. The solution framework is based on memetic algorithm concepts with a structured population. Case studies with a large network and real-world scenarios were used to evaluate the methodology. The results indicate that significant cost reductions can be achieved using the proposed solutions.

Reliability Modeling and Analysis of IEC 61850 Based Substation Protection Systems

This paper proposes a novel reliability modeling and analysis methodology for modern substation protection systems. A typical IEC 61850 based substation protection system is designed and analyzed using this methodology as an example. This system includes cyber components such as Merging Units (MUs), Intelligent Electronic Devices (IEDs), and process bus, as well as physical components such as transformers, circuit breakers, and transmission lines. A general technique for cyber-physical system reliability analysis and the concept of cyber-physical interface matrix are presented. The failure modes of individual components and their impacts on the overall system are modeled and numerically analyzed. The utility of the cyber-physical interface matrix in the reliability analysis of a composite power system is also illustrated. The cyber-physical interface matrix is the critical idea that helps making the analysis tractable. The results of our study provide important and precise information for substation reliability evaluation and pave the way for the reliability analysis of complex and large scale cyber-physical systems.

Stochastic Performance Assessment and Sizing for a Hybrid Power System of Solar/Wind/Energy Storage

This paper proposes a stochastic framework for optimal sizing and reliability analysis of a hybrid power system including the renewable resources and energy storage system. Uncertainties of wind power, photovoltaic (PV) power, and load are stochastically modeled using autoregressive moving average (ARMA). A pattern search-based optimization method is used in conjunction with a sequential Monte Carlo simulation (SMCS) to minimize the system cost and satisfy the reliability requirements. The SMCS simulates the chronological behavior of the system and calculates the reliability indices from a series of simulated experiments. Load shifting strategies are proposed to provide some flexibility and reduce the mismatch between the renewable generation and heating ventilation and air conditioning loads in a hybrid power system. Different percentages of load shifting and their potential impacts on the hybrid power system reliability/cost analysis are evaluated. Using a compromise-solution method, the best compromise between the reliability and cost is realized for the hybrid power system.

Reliability and Sensitivity Analysis of Composite Power Systems Under Emission Constraints

In view of the increasing role of environmental considerations in power generation, there is an evolving body of reliability methods that are cognizant of these emerging factors. This paper presents a method for analyzing the reliability of composite power systems under the constraints of CO2, SO2, and NOx emissions. It also utilizes the concept of the shadow price to perform sensitivity analysis with respect to these constraints. The method presented here uses a linearized power flow representation in the form of a linear programming (LP) model similar to those frequently used in power system reliability studies. In addition to power balance and flow constraints normally used, this work introduces a suitably formulated set of emission constraints. The dual solution of the LP provides the shadow prices that are used for determining the sensitivities. This paper also develops relationships for the sensitivities of several reliability indices with respect to the emission allowances. The method is demonstrated on the IEEE-RTS and the results are presented.

Primary energy congestion of power systems

Primary energy has the potential to bring challenges to the reliability, economic, and eco-friendliness of global electric power systems. The concept of electric power security are proposed, including many factors that are not considered in power system reliability analysis, such as coal supply for power system, fuel price for elec- tricity power market, carbon emissions of power genera- tion, and so on. It is broader than power system reliability and security, which means that providing energy in the form of reliable, economical, and eco-friendly electric power. Following an account of existing blackout defence methods and systems, the processes of transforming vari- ous kinds of primary energy into electric power and the interactions between them are described, particularly with regard to flows of energy, capital, and information. Factors that limit the liquidity of these flows are defined as ''gen- eralized congestion'', and the challenges presented by primary energy are named ''primary energy congestion''. China's dilemma on coal supply for power generation is presented in some detail as an example of primary energy congestion. To cope with impacts of the primary energy on electric power systems, an idea is introduced to extend the scope of existing coordinated blackout defence systems to account for primary energy, which would lead to an integrated tool to provide decision support to power system operators accounting for primary energy congestion.

Optimization Models and Methods Developed at the Energy Systems Institute

The paper presents shortly some optimization models of energy system operation and expansion that have been created at the Energy Systems Institute of the Siberian Branch of the Russian Academy of Sciences. Consideration is given to the optimization models of energy development in Russia, a software package intended for analysis of power system reliability, and model of flow distribution in hydraulic systems. A general idea of the optimization methods developed at the Energy Systems Institute is given including the reduced gradient method, interior point algorithms, method of modified Lagrange function, and cutting-plane algorithms.

The Selection of Power Supply Mode Based on Reliability's Social Costs

Selecting the power supply mode for important power consumers involves two aspects of reliability and economy. Combining with the power system reliability analysis method and taking full account of each component failure mode and their combination patterns, this paper embarks from the reality, accurately calculated the reliability indices of these power supply modes by minimal-cut sets, and then used the reliability indices to estimate the power losses of the users, finally used the theory of reliability cost-benefit and took the minimizing social costs that consist of reliability costs and outage losses as the goal to compare and analyze the reliability cost and the users outage losses under different power supply modes, obtained the suitable power supply mode for different important level of users.

Model for Power Shortage Estimation in Electric Power Systems

This paper addresses the model for power shortage estimation in electric power systems. The model’s main component of methodology for analysis of electric power system (EPS) reliability that has been developed at the Energy Systems Institute, Siberian Branch of Russian Academy Sciences. The methodology is based on the Monte-Carlo method. Quality and implementation time of reliability analysis depend on realization of the model. The model is implemented in the computational software for electric power systems reliability analysis. The history of evolution of the model for power shortage estimation and mathematical properties of the model are discussed. The results of the state-of-the-art studies of the model for power shortage estimation in EPS are presented. The model for power shortage estimation in EPS with quadratic power losses in power lines is considered. Algorithms of the interior point method with quadratic approximations of constraints applied for realization of the model are discussed. Results of experimental studies of the algorithms are presented.

The use of Extended Petri Nets in Analyzing the Reliability of MV / LV Distribution Transformer Stations

The article presents the results of a verification of the suitability of a method based on extended Petri nets to determine the indicators as well as the reliability characteristics of power stations. The author presented the theoretical basis of extended Petri nets. He conducted simulation of a station failure, using a program based on the rules of a Petri net, and a reliability analysis based on empirical data from service stations. He made a comparison of the coefficients and the properties of reliability obtained by both methods , yielding similar results. Based on the analysis, the author concluded that Petri nets are a very convenient and accurate tool to perform reliability analysis of complex power systems. Ill. 8, bibl. 9, tabl. 2 (in English; abstracts in English and Lithuanian). DOI: http://dx.doi.org/10.5755/j01.eee.121.5.1645

Risk analysis of critical infrastructures emphasizing electricity supply and interdependencies

Failures in critical infrastructures can cause major damage to society. Wide-area interruptions (blackouts) in the electricity supply system have severe impacts on societal critical functions and other critical infrastructures, but there is no agreed-upon framework on how to analyze and predict the reliability of electricity supply. Thus, there is a need for an approach to cross-sector risk analyses, which facilitates risk analysis of outages in the electricity supply system and enables investigation of cascading failures and consequences in other infrastructures. This paper presents such an approach, which includes contingency analysis (power flow) and reliability analysis of power systems, as well as use of a cascade diagram for investigating interdependencies. A case study was carried out together with the Emergency Preparedness Group in the city of Oslo, Norway and the network company Hafslund Nett. The case study results highlight the need for cross-sector analyses by showing that the total estimated societal costs are substantially higher when cascading effects and consequences to other infrastructures are taken into account compared to only considering the costs of electricity interruptions as seen by the network company. The approach is a promising starting point for cross-sector risk analysis of electricity supply interruptions and consequences for dependent infrastructures.

Improvement In Reliability Of Composite Power System Using Tcsc, Upfc Of 6 Bus Rbts – A Comparison

Emerging techniques for composite power system reliability evaluation mainly focus on conventional generation and transmission facilities. Reliability analysis of composite power system is determined by applying the FACTS devices like UPFC & TCSC in IEEE 6 Bus RBTS system at different buses & transmission lines. In this paper, a comparison is carried out between the systems using UPFC, TCSC in order to describe which FACTS device is best suitable for the system. The comparison is made in different parameters via. availability & unavailability, System Indices, Probability of Failure & Expected Energy Not Supplied (EENS), by considering different modules & bus numbers of the composite power system. Keywords - UPFC, TCSC, Reliability, EENS, Probability of Failure, System Indices.

Latin Hypercube Sampling Techniques for Power Systems Reliability Analysis With Renewable Energy Sources

This paper proposes Latin hypercube sampling (LHS) methods for reliability analysis of power systems including renewable energy sources, with an emphasis on the fluctuation of bus loads and intermittent behavior of renewable generations such as wind and solar power. The LHS methods that are applicable for systems with correlated random variables-system load and renewable generation-are proposed. Reliability indices such as loss of load expectation and loss of load probability are estimated. Results from Monte Carlo (MC) sequential sampling, MC nonsequential sampling, and that from the proposed LHS methods are compared. It is shown that the proposed methods are as accurate as the other sampling methods while requiring much less CPU time. Two case studies modified from the Electric Reliability Council of Texas (ERCOT) and IEEE Reliability Test System (IEEE RTS) are presented to demonstrate the performances of the proposed sampling methods.

Advantages and difficulties with the application of methods of probabilistic safety assessment to the power systems reliability

Abstract The probabilistic safety assessment is a standardized and widely accepted method for assessing and improving the reliability and safety of complex technologies, which is particularly true for the nuclear and the aerospace industry. The number of its applications to reliability of power systems is increasing. The objective of the paper is to collect and present the advantages and difficulties with the application of methods of probabilistic safety assessment to power systems reliability. The methods which apply the features of fault tree analysis to reliability analysis of power systems are presented and compared. The results are discussed and evaluated. The main advantages are connected with the facts that the methods are relative simple, the models are mostly available and that the data is intensively collected, evaluated and can serve as an excellent support for the quantitative part of the analyses. The difficulties are connected with different nature of components interaction within the power system compared to the safety systems in a nuclear power plant and with the large complexity of the power system, which distinguishes the term reliability into its static and dynamic parts known as adequacy and security. The results show large impact of common cause failures. The lack of data for the evaluations in the field of common cause failures of power systems increases significantly the uncertainty of the results. The uncertainty of the results may be reduced by improved data collection and analysis similarly as it is done in the nuclear safety.