Battery Degradation Maps for Power System Optimization and as a Benchmark Reference

This paper presents a novel method to describe battery degradation. We use the concept of degradation maps to model the incremental charge capacity loss as a function of discrete battery control actions and state of charge. The maps can be scaled to represent any battery system in size and power. Their convex piece-wise affine representations allow for tractable optimal control formulations and can be used in power system simulations to incorporate battery degradation. The map parameters for different battery technologies are published making them an useful basis to benchmark different battery technologies in case studies

Linear/Quadratic Programming-Based Optimal Power Flow using Linear Power Flow and Absolute Loss Approximations

This paper presents novel methods to approximate the nonlinear AC optimal power flow (OPF) into tractable linear/quadratic programming (LP/QP) based OPF problems that can be used for power system planning and operation. We derive a linear power flow approximation and consider a convex reformulation of the power losses in the form of absolute value functions. We show four ways how to incorporate this approximation into LP/QP based OPF problems. In a comprehensive case study the usefulness of our OPF methods is analyzed and compared with an existing OPF relaxation and approximation method. As a result, the errors on voltage magnitudes and angles are reasonable, while obtaining near-optimal results for typical scenarios. We find that our methods reduce significantly the computational complexity compared to the nonlinear AC-OPF making them a good choice for planning purposes

Transmission Network Reduction Method using Nonlinear Optimization

This paper presents a new method to determine the susceptances of a reduced transmission network representation by using nonlinear optimization. We use Power Transfer Distribution Factors (PTDFs) to convert the original grid into a reduced version, from which we determine the susceptances. From our case studies we find that considering a reduced injection-independent evaluated PTDF matrix is the best approximation and is by far better than an injection-dependent evaluated PTDF matrix over a given set of arbitrarily-chosen power injection scenarios. We also compare our nonlinear approach with existing methods from literature in terms of the approximation error and computation time. On average, we find that our approach reduces the mean error of the power flow deviations between the original power system and its reduced version, while achieving higher but reasonable computation times

Transmission Network Reduction Method using Nonlinear Optimization

This paper presents a new method to determine the susceptances of a reduced transmission network representation by using nonlinear optimization. We use Power Transfer Distribution Factors (PTDFs) to convert the original grid into a reduced version, from which we determine the susceptances. From our case studies we find that considering a reduced injection-independent evaluated PTDF matrix is the best approximation and is by far better than an injection-dependent evaluated PTDF matrix over a given set of arbitrarily-chosen power injection scenarios. We also compare our nonlinear approach with existing methods from literature in terms of the approximation error and computation time. On average, we find that our approach reduces the mean error of the power flow deviations between the original power system and its reduced version

A Framework for and Assessment of Demand Response and Energy Storage in Power Systems

AbstractThe shift in the electricity industry from regulatedmonopolies to competitive markets as well as the wide-spreadintroduction of fluctuating renewable energy sources bring newchallenges to power systems. Some of these challenges can bemitigated by using demand response (DR) and energy storageto provide power system services. The aim of this paper is toprovide a unified framework that allows us to assess differenttypes of DR and energy storage resources and determine whichresources are best suited to which services.We focus on four resources: batteries, plug-in electric vehicles,commercial buildings, and thermostatically controlled loads. Wedefine generic power system services in order to assess theresources. The contribution of the paper is threefold: (i) thedevelopment of a framework for assessing DR and energy storageresources; (ii) a detailed analysis of the four resources in terms ofability for providing power system services, and (iii) a comparisonof the resources, including an example case for Switzerland.We find that the ability of resources to provide power systemservices varies largely and also depends on the implementationscenario. Generally, there is large potential to use DR and energystorage for providing power system services, but there are alsochallenges to be addressed, for example, adequate compensation,privacy, guaranteeing costumer service, etc.24 Halama