Active local distribution network management for embedded generation

Traditionally, distribution networks have been operated as passive networks with uni-directional power flows. With the connection of increasing amounts of distributed generation, these networks are becoming active with power flowing in two directions, hence requiring more intelligent forms of management. The report into issues for access to electricity networks published by the Ofgem/DTI Embedded Generation Working Group in January 2001 called for new work in the area of active distribution network management. The report suggested an evolution from the present passive network control philosophy to fully active network control methods. In line with these recommendations Econnect is developing a new type of distribution network controller, called GenAVC. GenAVC is a controller for electricity distribution networks that aims to increase the amount of energy that can be exported onto the distribution networks by generating plants. The UK is leading the world in electricity de-regulation and one aspect of this is the increasing demand for the connection of distributed generation. Active distribution network management is seen to be essential for networks to accommodate the levels of distributed generation that are predicted for 2010. The work being undertaken as part of this project is therefore at the forefront of international network management technology

State estimation applied to active distribution networks with minimal measurements

Traditionally, state estimation is applied to transmission networks to improve security and redundancy of the measurement system. This paper describes the application of state estimation to distribution networks in order to extend the observability of the network. Key features of this application are that the network is active, minimal real measurements are available and that there is minimal communications infrastructure. this paper presents results ffrom a field trial whihc manages voltages in an 11kV distribution network with distributed generation. The paper highlights the problems associated with this application and presents some solutions

Steady state and mean recurrence time for random walks on stochastic temporal networks

Random walks are basic diffusion processes on networks and have applications in, for example, searching, navigation, ranking, and community detection. Recent recognition of the importance of temporal aspects on networks spurred studies of random walks on temporal networks. Here we theoretically study two types of event-driven random walks on a stochastic temporal network model that produces arbitrary distributions of interevent-times. In the so-called active random walk, the interevent-time is reinitialized on all links upon each movement of the walker. In the so-called passive random walk, the interevent-time is only reinitialized on the link that has been used last time, and it is a type of correlated random walk. We find that the steady state is always the uniform density for the passive random walk. In contrast, for the active random walk, it increases or decreases with the node's degree depending on the distribution of interevent-times. The mean recurrence time of a node is inversely proportional to the degree for both active and passive random walks. Furthermore, the mean recurrence time does or does not depend on the distribution of interevent-times for the active and passive random walks, respectively.Comment: 5 figure

Choice of State Estimation Solution Process for Medium Voltage Distribution Systems

As distribution networks are turning into active systems, enhanced observability and continuous monitoring becomes essential for effective management and control. The state estimation (SE) tool is therefore now considered as the core component in future distribution management systems. The development of a novel distribution system SE tool is required to accommodate small to very large networks, operable with limited real time measurements and able to execute the computation of large volumes of data in a limited time frame. In this context, the paper investigates the computation time and voltage estimation qualities of three different SE optimization solution methods in order to evaluate their effectiveness as potential distribution SE candidate solutions

Digital Current-Control Schemes

The paper is about comparing the performance of digital signal processor-based current controllers for three-phase active power filters. The wide use of nonlinear loads, such as front-end rectifiers connected to the power distribution systems for dc supply or inverter-based applications, causes significant power quality degradation in power distribution networks in terms of current/voltage harmonics, power factor, and resonance problems. Passive LC filters (together with capacitor banks for reactive power compensation) are simple, low-cost, and high-efficiency solution

Linear Approximations to AC Power Flow in Rectangular Coordinates

This paper explores solutions to linearized powerflow equations with bus-voltage phasors represented in rectangular coordinates. The key idea is to solve for complex-valued perturbations around a nominal voltage profile from a set of linear equations that are obtained by neglecting quadratic terms in the original nonlinear power-flow equations. We prove that for lossless networks, the voltage profile where the real part of the perturbation is suppressed satisfies active-power balance in the original nonlinear system of equations. This result motivates the development of approximate solutions that improve over conventional DC power-flow approximations, since the model includes ZIP loads. For distribution networks that only contain ZIP loads in addition to a slack bus, we recover a linear relationship between the approximate voltage profile and the constant-current component of the loads and the nodal active and reactive-power injections