Pair Of Buses Research Articles

Probabilistic optimal siting and sizing of distributed generation and shunt capacitors considering feeder flow control units using a novel distribution power flow

A modern energy system should be reliable, economically viable, and environment-friendly. This paper addresses the above issue by proposing a probabilistic approach of optimally placing and sizing distributed generation and shunt capacitors in a distribution network. Objectives are to simultaneously reduce the cost, emission, network loss, improve the system voltage profile, and avoid line overloads. A feeder flow control generator is considered so that the distribution network draws a constant amount of active and reactive power from the substation. The operation is modeled using a Zero-PQVδ bus pair in the power flow. A novel distribution system power flow is proposed to embody the operation philosophy. Uncertainties of renewable power sources and load demand are modeled using ‘Hong's 2m point estimate method’. A fuzzy multi-objective satisfaction criterion is used to realize multiple objectives. Simulation studies on a thirty-three node distribution network reveal the efficacy of the proposed method.

A novel [formula omitted] bus pair method of biomass DGs placement in distribution networks to maintain the voltage of remotely located buses

This paper proposes a new DG placement and sizing technique by introducing a novel Q−PQV bus pair in distribution networks (DNRs) with seasonal variation of load demand. The principle aim of this paper is to boost and maintain the voltage of remotely located buses to predefined optimal level for seasonal load demand by integrating biomass DGs in DNRs. The selection of locations and sizes of DGs is determined by novel bus pair, which is different from conventional buses present in power system studies. For PQV bus along with active and reactive power, the voltage magnitude also is known, whereas, for Q bus, only reactive power is known. The power injection of Q bus with the load connected determines DG sizes. The inclusion of this new bus pair modifies the load flow technique, which is also given in the paper. The proposed methodology is applied on 33 bus DNR, while active power loss is taken as principal objective function. Both upf and lpf DGs are considered in this paper, and the results are compared with existing methods available in literature. The cost-benefit analysis shows the profit gained from it.

Generator Coherency and Network Partitioning for Dynamic Equivalencing Using Subtractive Clustering Algorithm

In this paper, a new method called subtractive clustering is presented to partition a power system into areas after a disturbance occurs. Subtractive clustering is basically used as a preprocessing step for other clustering methods to overcome their shortcomings, such as the need to predefine the number of areas and high dependency to random functions. However, due to the special characteristics of power systems, this method itself can be used to find areas. In subtractive method, the degree of coherency between all buses is used to form a density value for each bus. To calculate the degree of coherency between buses, the frequency components existing in the angular velocity variation of voltage phasors, in the range of interarea and local oscillation modes, are extracted. Then, the correlation between the real parts of these frequencies and the correlation between the imaginary parts are calculated individually. This means that the coherency between each pair of buses is assessed in two dimensions, which results in more efficient dynamic coherency identification. The capability of the proposed method is demonstrated for disturbances applied on the 16-machine, 68-bus system. It is observed that subtractive method is highly appropriate to find coherent areas for different disturbances.

Network-Based Analysis of Small-Disturbance Angle Stability of Power Systems

This paper investigates small-disturbance angle stability of power systems with emphasis on the role of power network topology, which sheds new light on the instability mechanism. We introduce the concepts of active power flow graph and critical lines. It is shown that the inertia of the Laplacian matrix of this graph provides information on the stability and type of an equilibrium point. Then, the instability mechanism is elaborated from the impact of critical lines on the inertia of the Laplacian matrix. A stability criterion in terms of a critical line-based matrix is established. This criterion is a necessary and sufficient condition to judge the stability and type of an equilibrium point. It includes the existing results in the literature and applies to the unsolved cases where the critical lines exist but do not form cutsets. Moreover, we introduce the concept of equivalent weight between a pair of buses. Another stability criterion in terms of the equivalent weight is developed, from which the small-disturbance instability can be interpreted as the “electrical antagonism” between some buses in the power network resulting from the critical lines. The equivalent weight can also be used as a stability index and provides guidance for system operation. The obtained results are illustrated by numerical simulations.

Simulating the Travel Time Impact of Missed Transit Connections

It is well established that transit passengers dislike transferring, in part because of the inherent risk that the connecting vehicle will be missed, a risk that can increase overall travel time. Despite the problems that missed transfers cause, such transfers across a system are rarely tracked in transit performance monitoring programs. The likelihood of a missed transfer depends on combinations of several factors and thus is hard to estimate. In practice, transit systems are most often evaluated according to the performance of individual vehicles, stops, and routes, not the interactions between them. This paper describes a systems approach to quantify the effects of travel time reliability, schedule adherence, and schedule design on missed transit connections, and the resulting travel time distributions. To determine the effects of vehicle interactions on transfers and the role that transfers play in travel time, a series of simulations based on automatic passenger counting data from the bus system in San Diego, California, was performed. Travel times on two transfer trips in downtown San Diego were simulated. The effects of passenger arrival rate, on-time vehicle performance, and schedule design on the likelihood of a transfer being missed were investigated in a sensitivity analysis. This research is expected to lead to a better understanding of the passenger effects of schedule adherence on transfer trips. Practically speaking, this methodology could aid in the identification of pairs of buses whose chronic schedule deviations at a particular location are likely causing missed transfers.

New approach for power network clustering using a representative model

A new power network model that is suitable for network clustering techniques is presented. The method is based on representing the system buses as modules and the connecting branches as nets. The number of nets connecting each pair of modules is chosen to be a function of either a single electrical property or a normalised combination of several properties of the equivalent branch connecting the pair of buses. A heuristic approach, based on the approximation of the constrained network partitioning problem into a linear transportation problem, is used to cluster the network into S clusters each containing m buses. The use of a linear-time bus interchange algorithm provides the best possible cluster configuration. The solution technique provides complete freedom in choosing the electrical properties of the greatest importance to the clustering application. Consequently, the selectivity of the proposed solution technique in the aspect of choosing the electrical connectivity measure is evident.

Application of partitioning techniques for decomposing large-scale electric power networks

Two efficient heuristic algorithms for solving cluster problems associated with partitioning of power networks are presented in this paper. Both algorithms are divided into two stages. In the first stage, an initial partition is created based on the electrical distance among system buses. The second stage involves interchanging pairs of buses among the various clusters of the initial partition. The first algorithm solves an optimal k-decomposition problem. In the optimal k-decomposition, the partitioning of a network into k clusters of buses is performed by maximizing the number of uncut links among clusters. This type of decomposition is known to be equivalent to a 0–1 quadratic programming problem which is approximated by a linear transportation problem. By defining a link weight as the electrical distance between linking buses, the algorithm clusters strongly-connected buses together while weakly-connected buses are placed in different clusters. The second algorithm solves the placement problem of n-connected buses in a k-dimensional Euclidean space; such a problem is reduced to finding k eigenvectors of a connectivity matrix, defined as the bus admittance matrix. The node interchange is an iterative heuristic method that can be used to improve an initial partition, such as that obtained by either the k-decomposition technique or the eigenvector approach. The method moves one bus at a time, from one cluster of the initial partition to another, in an attempt to maximize the total electric distance among clusters of the final partition. Applications of the proposed algorithms to both small and medium-size power systems, and comparing the results with those obtained in another study, are illustrated in this paper.

A heuristic algorithm for power-network clustering

An efficient heuristic algorithm for solving cluster problems associated with partitioning of power networks is presented. The algorithm is divided into two stages. The first stage creates an initial partition based on the electrical distance between system buses. The second stage involves interchanging pairs of buses among the various clusters of the initial partition. The first stage solves the placement problem of n connected buses in an r-dimensional Euclidean space; such a problem is reduced to finding r eigenvectors of a connectivity matrix, defined as the bus admittance matrix. The second stage is based on a node interchange technique. The node interchange is an iterative heuristic method that can be used to improve an initial partition. The method moves one bus at a time, from one cluster of the initial partition to another, in an attempt to maximize the total electrical distance between clusters of the final partition. Applications of the proposed algorithm to both small and medium-size power systems are illustrated.

Air Force Armament Laboratory (AFATL) battery power supply (BPS) operations and maintenance (EM launchers)

The successful operation of the AFATL BPS system is discussed in terms of its proven reliable performance record, flexibility to adapt to different test configurations, and relatively inexpensive operating maintenance costs per test. The BPS consists of 13728 batteries, interconnecting buswork, and a power conditioning inductor. The system is subdivided into six modules, each divided into six gangs with its own gang switch, each gang containing 24 battery strings. Each module has its own main bus pair, with the negative bus common and the positive bus switched. Realizing that batteries are a perishable product, the operational and performance history of the AFATL BPS has nevertheless proven that this battery system is effective as a prime power supply for hypervelocity launcher research. Turn-around time between tests has generally been less than that required for the test article. The power capabilities of the BPS can easily be expanded to the design point of a 200 MJ energy store. This can be done by adding more modules of batteries and reconfiguring the inductor with its existing three auxiliary turns in series.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>