No abstract

This paper presents a method for tracking a secondary frequency control (Load Frequency Control) signal by groups of plug-in hybrid electric vehicles (PHEVs), controllable thermal household appliances under a duty-cycle coordination scheme, and a decentralized combined-heat-and-power generation unit. The distribution of the control action on the participating units is performed by an aggregator utilizing a Model Predictive Control strategy which allows the inclusion of unit and grid constraints. In addition to the individual dynamic behavior, the varying availability of the units during the day is taken into account. The proposed methodology, easily extendable to larger networks, is evaluated on a four-bus system corresponding to a medium-voltage distribution grid and illustrates a possible operation mode of an aggregator in the power system.Index Terms-Aggregators, cogeneration, electric appliances, Load Frequency Control (LFC), load management, plug-in hybrid electric vehicles (PHEVs), smart grids, vehicle to grid (V2G), virtual power plants.

No abstract

Abstract-The system-level consideration of intermittent renewable energy sources and small-scale energy storage in power systems remains a challenge as either type is incompatible with traditional operation concepts. Non-controllability and energy-constraints are still considered contingent cases in market-based operation. The design of operation strategies for up to 100 % renewable energy systems requires an explicit consideration of non-dispatchable generation and storage capacities, as well as the evaluation of operational performance in terms of energy efficiency, reliability, environmental impact and cost. By abstracting from technology-dependent and physical unit properties, the modeling framework presented and extended in this paper allows the modeling of a technologically diverse unit portfolio with a unified approach, whilst establishing the feasibility of energy-storage consideration in power system operation. After introducing the modeling approach, a case study is presented for illustration.

In this paper, a novel load management approach using thermal household appliances is presented, which provides extensive possibilities to support power system control tasks. A recently developed coordination algorithm for a high number of small thermostat-controlled appliances requires the connection of individual appliances to a central control entity through a twoway communication channel. The control method, which does not cause significant comfort losses for users, enables the group of appliances to act like a virtual distributed energy storage. While the coordination algorithm has been presented in detail before, the contribution of this paper lies in the analysis of the aggregated behavior of coordinated appliance groups. Apart from that, a methodology for estimating the coordinated load control potential in larger areas (e.g. countries) is presented. This is illustrated by exemplary considerations on the Swiss power system, which can also be adapted to other countries. Furthermore, different applications for the gained demand-side flexibility in a liberalized electricity market are discussed.

We present a novel global 3-D electromagnetic (EM) inverse solution that allows to work in a unified and consistent manner with frequency-domain data that originate from ionospheric and magnetospheric sources irrespective of their spatial complexity. The main idea behind the approach is simultaneous determination of the source and conductivity distribution in the Earth. Such a determination is implemented in our solution as a looped sequential procedure that involves two steps: (1) determination of the source using a fixed 3-D conductivity model and (2) recovery of a 3-D conductivity model using a fixed source. We focus in this paper on analysis of Sq data and numerically verify each step separately and combined using data synthesized from 3-D models of the Earth induced by a realistic Sq source. To determine the source we implement an approach that makes use of a known conductivity structure of the Earth with non-uniform oceans. Based on model studies we show that this approach outperforms the conventional potential method. As for recovery of 3-D conductivity in the mantle, our inverse scheme relies on a regularized least-square formulation, exploits a limited-memory quasi-Newton optimization method and makes use of the adjoint source approach to calculate efficiently the misfit gradient. We perform resolution studies with checkerboard conductivity structures at depths between 10 and 1600 km for different inverse setups and conclude from these studies that: (1) inverting Z component gives much better results than inverting all (X, Y and Z) components; (2) data from the Sq source allows for resolving 3-D structures in depth range between 100 and 520 km; (3) the best resolution is achieved in the depth range of 100-250 km.

 Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

No abstract