Effective monitoring and management applications on modern distribution networks require a sound network model and the knowledge of line parameters. Network line impedances are used, among other things, for state estimation and protection relay setting. Phasor Measurement Units (PMUs) give synchronized voltage and current phasor measurements, referred to a common time reference (coordinated universal time). All synchrophasor measurements can thus be temporally aligned and coordinated across the network. This feature, along with high accuracy and reporting rates, could make PMUs useful for the evaluation of network parameters. However, instrument transformer behavior strongly affects parameter estimation accuracy. In this paper, a new PMU-based iterative line parameter estimation algorithm for distribution networks, which includes in the estimation model systematic measurement errors, is presented. This method exploits the simultaneous measurements given by PMUs on different nodes and branches of the network. A complete analysis of uncertainty sources is also performed, allowing the evaluation of estimation uncertainty. Issues related to operating conditions, topology and measurement uncertainty are thoroughly discussed and referenced to a realistic model of a distribution network to show how a full network estimator is possible.
Abstract-Optimization of distributed power assets is a powerful tool that has the potential to assist utility efforts to ensure customer voltages are within pre-defined tolerances and to improve distribution system operations. While convex relaxations of Optimal Power Flow (OPF) problems have been proposed for both balanced and unbalanced networks, these approaches do not provide universal convexity guarantees and scale inefficiently as network size and the number of constraints increase. In balanced networks, a linearized model of power flow, the LinDistFlow model, has been successfully employed to solve approximate OPF problems quickly and with high degrees of accuracy. In this work, an extension of the LinDistFlow model is proposed for unbalanced distribution systems, and is subsequently used to formulate an approximate unbalanced OPF problem that uses VAR assets for voltage balancing and regulation. Simulation results on the IEEE 13 node test feeder demonstrate the ability of the unbalanced LinDistFlow model to perform voltage regulation and balance system voltages.
The availability of accurate measurements is the prerequisite for the actual implementation of many monitoring and management applications in smart distribution networks. Phasor Measurement Units (PMUs) can provide synchronized voltage and current measurements, referred to a common time reference (usually the Coordinated Universal Time, UTC). This feature, as well as the high accuracy and reporting rate of PMUs, can be exploited for an accurate network monitoring. At the same time, the smartness of the grid can include the possibility for the measurement system to self-detect its weak points and improve its performance. In this perspective, a technique for the estimation and the compensation of systematic errors existing in the components of a PMU-based distributed measurement system suitable for monitoring three-phase distribution networks is presented. The uncertainty induced by the components of the measurement system, mainly instrument transformers and PMUs, is included in the model, along with the uncertainty affecting the values of the network line parameters. The method exploits the possible constraints introduced by the grid topology (presence of multiple lines, injected currents, etc.) to improve the accuracy of the estimation, so that a proper compensation of the estimated errors can be allowed. The validity of the approach is verified though simulations performed on a small portion of a test medium voltage distribution grid.
We propose an innovative framework termed phasor-based control (PBC) to facilitate the integration of heterogeneous and intermittent distributed energy resources (DER) on the electric grid. PBC presents a unified approach that is agnostic to optimization criteria and to the particular characteristics of participating resources. It is enabled by synchronized, high-precision voltage phasor measurements that allow stating control objectives in grid-specific, rather than resource-specific, terms. We present qualitative justification and examine the general feasibility of this control approach, including the behavior of candidate control algorithms in simulation. Initial results suggest that PBC has significant potential to support stable and resilient grid operations in the presence of arbitrarily high penetrations of DER.
The smart grid revolution is creating a paradigm shift in distribution networks that is marked by new, significant intermittencies and uncertainties in power supply and demand. These developments include the dramatic increase in the adoption of distributed energy resources (DER), electric vehicles, energy storage, and controllable loads. This transformation imposes new challenges on existing distribution infrastructure and system operations for stockholders, engineers, operators and customers. Unfortunately, distribution networks historically lag behind transmission networks in terms of observability, measurement accuracy, and data granularity. The changes in the operation of the electric grid dramatically increase the need for tools to monitor and manage distribution networks in a fast, reliable and accurate fashion. This paper describes the development process of a network of high-precision micro phasor measurement units or µPMUs, beginning with an overview of the µPMU technology that provides synchronous measurements of voltage phase angles, or synchrophasors. Next, the µPMU network and communications infrastructure are discussed, followed by an analysis of potential diagnostic and control applications of µPMU data in the electric grid at the distribution level.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.