Power-flow study

About: Power-flow study is a research topic. Over the lifetime, 8091 publications have been published within this topic receiving 155053 citations. The topic is also known as: load-flow study.

Hierarchical Spectral Clustering of Power Grids

Abstract: A power transmission system can be represented by a network with nodes and links representing buses and electrical transmission lines, respectively. Each line can be given a weight, representing some electrical property of the line, such as line admittance or average power flow at a given time. We use a hierarchical spectral clustering methodology to reveal the internal connectivity structure of such a network. Spectral clustering uses the eigenvalues and eigenvectors of a matrix associated to the network, it is computationally very efficient, and it works for any choice of weights. When using line admittances, it reveals the static internal connectivity structure of the underlying network, while using power flows highlights islands with minimal power flow disruption, and thus it naturally relates to controlled islanding. Our methodology goes beyond the standard k-means algorithm by instead representing the complete network substructure as a dendrogram. We provide a thorough theoretical justification of the use of spectral clustering in power systems, and we include the results of our methodology for several test systems of small, medium and large size, including a model of the Great Britain transmission network.

A study of system splitting strategies for island operation of power system: a two-phase method based on OBDDs

Abstract: System splitting problem, also known as controlled system separation problem, is to determine the proper splitting points for splitting the entire power network into islands when island operation of system is unavoidable. By "proper" we mean that the splitting strategies should guarantee both the power balance and satisfaction to capacity constraints of transmission lines and other facilities in each island. The system splitting problem is very hard because the strategy space is huge for even middle-scale power networks. This paper proposes a two-phase method to search for proper splitting strategies in real-time. The method narrows down the strategy space using highly efficient OBDD-based algorithm in the first phase, then finds proper splitting strategies using power-flow analysis in the reduced strategy space in the second phase. Simulation with symbolic model checking tool SMV indicates that this method is very promising.

A novel single-phase power factor correction scheme

Abstract: A single-phase power factor correction scheme is proposed based on the power flow analysis. It is found that the conventional power factor correction (PFC) circuit must be designed to handle the rated power, although its purpose is only for power factor correction. With the proposed scheme, the PFC circuit is in parallel with the major power flow path, thus reducing its size and weight compared to a conventional two-cascade-stage scheme. A prototype circuit is built and tested to verify this concept. >

Geometry of Power Flows and Optimization in Distribution Networks

Abstract: We investigate the geometry of injection regions and its relationship to optimization of power flows in tree networks. The injection region is the set of all vectors of bus power injections that satisfy the network and operation constraints. The geometrical object of interest is the set of Pareto-optimal points of the injection region. If the voltage magnitudes are fixed, the injection region of a tree network can be written as a linear transformation of the product of two-bus injection regions, one for each line in the network. Using this decomposition, we show that under the practical condition that the angle difference across each line is not too large, the set of Pareto-optimal points of the injection region remains unchanged by taking the convex hull. Moreover, the resulting convexified optimal power flow problem can be efficiently solved via semi-definite programming or second-order cone relaxations. These results improve upon earlier works by removing the assumptions on active power lower bounds. It is also shown that our practical angle assumption guarantees two other properties: 1) the uniqueness of the solution of the power flow problem and 2) the non-negativity of the locational marginal prices. Partial results are presented for the case when the voltage magnitudes are not fixed but can lie within certain bounds.

Network power-flow analysis for a high penetration of distributed generation

Abstract: Summary form only given. The connection of large numbers of small or micro-generators to low voltage distribution networks may put at risk traditional network designs. Such designs are based on traditional assumptions such as historical diversity factors and other simplifying assumptions that may no longer be appropriate. This paper describes on-going research, based on a detailed examination of a typical low voltage distribution system with increasing penetrations of distributed generation, mostly in the form of micro-generators (micro-clip, building integrated wind, and building integrated photovoltaics) connected at domestic properties. Modelling techniques have been developed that are applicable to complete distribution feeders: from primary substations, through medium and low-voltage networks to individual single-phase customer connection points. The modelling uses accurate unbalanced power-flow analysis (load-flow) and 1-minute time-series load data. Provisional results show that statistically, in terms of voltage quality and line limits, higher than expected penetrations of distributed generation can be accommodated without modifications to the distribution system. System evolution is discussed with even higher penetrations in mind.