Bulk Power System Reliability Evaluation Research Articles

Simplified Sequential Simulation of Bulk Power System Reliability Via Chronological Probability Model of Load Supplying Capability

This paper proposes a simplified sequential Monte Carlo simulation to enhance the efficiency of bulk power system reliability evaluation. The basic idea is to construct chronological system state sequence by using the chronological probability model of load supplying capability which reflects the joint chronological variation pattern of system state intrinsic properties including load supplying capability ( C ), system state average duration ( D ), and splitting percentage ( P ). The chronological probability model can simplify sequential simulation procedure no matter how system load pattern changes, and avoid the time-consuming optimal load curtailment model calculations by using the above-mentioned system state intrinsic properties. Thus, the proposed method can considerably accelerate simulation, especially when evaluating system reliability for different system load conditions. Besides, as the proposed method retains the chronological property of system state transition, it can not only obtain the probability distribution of reliability indices but also incorporate time-dependent renewable generations. RBTS, RTS79, and modified RTS79 with wind farm are utilized to verify the effectiveness of the proposed method.

A model predictive control framework for reliable microgrid energy management

This paper proposes a framework for reliable microgrid energy management based on receding horizon control. A microgrid is considered for exemplification, connected to an external grid via a transformer and containing a local consumer, a renewable generator (wind turbine) and a storage facility (battery). Optimal scheduling of battery is sought for minimizing costs. To this aim, a predictive control framework is proposed, which allows taking into consideration cost values, power consumption and generation profiles, and specific constraints. Uncertainty due to variations in the generator model parameters is taken into account. The efficiency of the proposed approach is validated through simulation results and comparisons using real numerical data for a test system often considered in bulk power system reliability evaluation studies. The obtained results show that predictive control is a viable approach for providing optimal energy management solutions accounting for costs, profiles and constraints.

Power System Reliability Impact of Energy Storage Integration With Intelligent Operation Strategy

Electric power industry is experiencing a movement from the existing conventional electric grid to a more reliable, efficient and secure smart grid. In order to achieve these goals, components such as energy storage will be included, and potentially in large scale. Many feasible applications of energy storage in power systems have been investigated. The major benefits of energy storage include electric energy time-shift, frequency regulation and transmission congestion relief. In this paper, we focus on the reliability improvement of the bulk power system brought by the utilization of energy storage in the local distribution systems integrated with renewable energy generation. An intelligent operation strategy for energy storage which improves reliability considering the renewable energy integration is presented. The smart grid communication and control network is utilized to implement the proposed energy storage operation. A bulk power system reliability evaluation framework is proposed to study the reliability impact brought by the energy storage integration and operation. A detailed case study and sensitivity analysis is performed to demonstrate the effectiveness of the presented operation strategy and evaluation framework, and to provide valuable insights on the power system reliability impact derived from the energy storage integration.

Combining local and optimised power flow remedial measures in bulk reliability assessment

In traditional Newton-Raphson power flow algorithms, the terminal and remote bus voltages are obtained using a local control logic, i.e. reactive power and LTC taps are adjusted to meet pre-specified voltage settings. On the other hand, most of the optimal power flows (OPF) utilised in available reliability programs adopt an optimised logic for voltage control, i.e. the voltage level is optimised inside the pre-specified bounds, meaning that new settings can be calculated in order to avoid or minimise load shedding. However, in several practical situations this is not a feasible approach, due to operational constraints. Local voltage control logic is introduced into the non-linear interior point (IP) optimal power flow of a bulk power system reliability evaluation program in order to represent actual operational practices with increased accuracy. The impact of these two voltage control logics on the reliability indices is then analysed using the new IEEE Reliability Test System (RTS-96) and a 89-bus network derived from the North/Northeastern Brazilian System (NNBS).

A Framework Using Uncertainties in the Composite Power System Reliability Evaluation

In Bulk Power System Reliability Evaluation (BPSRE), realistic operating condition constraints are important issues. The limits based on stability and voltage considerations should be adhered to at all times to prevent blackouts, as voltage collapse problems account for uncertainties in power system operation, which is due to uncontrollable progressive decline in voltage. The aspects of uncertainties about future load growth, fuel cost, environmental regulations, etc., are difficult to specify properly within a long-term forecasting probabilistic model. On the other hand, the simple LP models are inadequate in satisfying realistic system objectives and constraints. Dynamical feature of load modeling may be critical in the computation of voltage collapse-related bulk power system reliability indices. Also, the control problem has attracted greater interest as the desire to transport power over longer distances has increased. In this work, while formulating mathematical formulation by considering the voltage collapse phenomena in the existing framework of BPSRE, the reactive power control variables are optimized by using Fuzzy linear programming. The uncertainties in system probabilistic parameters, like Forced Outage Rates, which affects largely the final indices, are also defined using the concept of Fuzzy Number and Linguistic variables. The new indices are found to reflect the integration of probabilistic models and fuzzy concepts. The proposed method has been tested on AEP-14 bus test system, and the results are compared with conventional ones and presented to demonstrate the effect of uncertainties in the system probabilistic parameters.

A Fuzzy Logic Approach to Security-Based Bulk Power System Reliability Evaluation

The most significant parameter in a bulk power adequacy assessment are the load point and overall system ''load curtailment indices''. Many utilities have difficulty in interpreting the calculated load curtailment indices, as the existing models do not always consider realistic and practical operating conditions. Simple linear programming formulations are found to be inadequate in satisfying realistic system objectives and constraints. The present paper models uncertainties in loads and generations as fuzzy numbers. The load curtailment indices (while load and generation being uncertain) are calculated using fuzzy linear programming. The proposed method is applied to the RBTS 6-bus and IEEE 14-bus test system. The results of the computation are optimistic in terms of minimization of the objective function compared to probabilistic approach, and these are more realistic. In the above application, contingency analysis has been carried out up to 2nd level, and contingencies that cause the system to go to extreme emergency state have been accounted for.

The IEEE Reliability Test System-1996. A report prepared by the Reliability Test System Task Force of the Application of Probability Methods Subcommittee

This report describes an enhanced test system (RTS-96) for use in bulk power system reliability evaluation studies. The value of the test system is that it will permit comparative and benchmark studies to be performed on new and existing reliability evaluation techniques. The test system was developed by modifying and updating the original IEEE RTS (referred to as RTS-79 hereafter) to reflect changes in evaluation methodologies and to overcome perceived deficiencies.

Application of an adequacy equivalent method in bulk power system reliability evaluation

A major difficulty in adequacy evaluation of composite generation and transmission or bulk power systems is the computation time required when the power system is large and high outage levels are investigated. A technique for studying the adequacy performance of a selected area (area of interest) in a power network in which the remaining network is modeled as an adequacy equivalent is presented in this paper. This approach can be useful in large power networks, where it is necessary to perform detailed adequacy evaluation of selected specific areas in the overall network. The equivalent approach can also be used to investigate the effects of high level outages, which may not be possible when the entire composite power network is considered. The basic concepts are illustrated using a simple radial power system. Applications and advantages of the proposed method are illustrated by presenting system study results for the IEEE two area Reliability Test System.

Topological analysis in bulk power system reliability evaluation

This paper presents a new computationally efficient methodology for calculating the reliability indices of a bulk power system using the state enumeration approach. The proposed approach utilizes topological analysis to determine the contribution of each system state to the frequency and duration indices at both the system and the bus level. In this approach, there is no need to conduct additional adequacy evaluations or utilize an optimization technique to identify the boundary wall between success and failure states. The effectiveness of the proposed methodology is demonstrated by application to the IEEE Reliability Test System (IEEE-RTS) and a model of the existing network of SaskPower in Canada. The proposed approach can also be used for noncoherent systems.

An analytical technique for bulk power system reliability evaluation

The increasing size and complexity of power systems, coupled with present day financial constraints, have made the use of probabilistic methods and reliability indices a necessity in order to maintain the continuity and quality of service to customers. For the combined generation and transmission system, that is, the bulk power system, concepts and models for reliability analysis are not as well established as they are for the generation or distribution systems. This paper presents a technique based on tie sets for computing the reliability indices such as probability of system failure for bulk power systems. The power system network is modelled as a transportation network so that the constraints on the real power flow in each line of the network are observed. The problem of bulk power system transmission reliability is then viewed as a reliability evaluation of a multinode capacitative network. A path set is defined to be the paths or combination of paths from the input node to the output node of a power system network such that the total system load is satisfied. In this method an upper bound to the probability of system failure is computed. A computer program has been developed to implement this method on a (DEC) VAX 11/785 computer. The performance of the method is analyzed with respect to the reliability of transmission lines as well as the magnitude of the system load.

A method for bulk power system reliability evaluation based on local coherency

Abstract The problem of bulk power system reliability evaluation is considered and a new solution approach is proposed. Bulk power system models are generally not coherent in the sense of reliability theory. Conditions are derived on network topology to guarantee coherency. Only parallel structure systems satisfy these conditions. Noncoherency of a power system may be the effect of only a subset of its transmission lines. Thus the concept of local coherency is introduced. A decomposition approach to bulk power system reliability evaluation based on the concept of local coherency is developed. Sufficient conditions for local coherency are derived.

Power System Reliability Evaluation Using Stochastic Load Flows

This paper presents a simulation procedure for bulk power system reliability evaluation. The operation of the system under forced or scheduled outages of circuits and/or units is simulated via a stochastic load flow. An efficient stochastic load flow methodology is presented, which computes circuit loading and bus voltage probability distributions from a given load probability distribution. The output of the stochastic load flow is utilized to compute the conditional probability of system failure according to predefined criteria. Circuit overloads and bus undervoltages/overvoltages are utilized as system failure criteria. The frequency and duration method is employed to compute bulk power system reliability indices. Upper and lower bounds on the reliability indices are computed, which converge to the true values of the indices as the number of contingencies simulated increases. The paper presents simulation results with two systems: (a) a small 9-bus system to demonstrate data requirements, and (b) the 500 kV/230 kV system of Georgia Power Company to demonstrate the applicability of the method to actual systems.