Electric Vehicle Charging Flexibility for Ancillary Services in the German Electrical Power System

Language
en
Document Type
Doctoral Thesis
Issue Date
2021-11-29
Issue Year
2021
Authors
Schlund, Jonas
Editor
Abstract

The transition to a sustainable energy economy is one of the key challenges of this century. Flexibility is crucial in order to integrate renewable energies into the power system. The intelligently coordinated charging of large amounts of electric vehicles results in a novel, sustainable flexibility source. To be able to use that flexibility to contribute to system stability, we first need to fully understand it and to be able to exactly quantify and manage it. This thesis solves these challenges using data-driven models and simulation with randomness. An in depth analysis of a large scale mobility survey in Germany provides the mobility and charging constraints of electric vehicles. The resulting behavior model is based on a Bayesian network and accurately models the behavior of different user groups. Adding technical model components we are able to simulate the vehicle grid interaction and to validate the results. A central component of the thesis is the novel FlexAbility concept, that allows for a quantification of flexibility reservation and ensures that individual charging constraints are not violated. It includes constraints in the dimensions of power, energy and time and methods for aggregation and disaggregation. The analysis shows that the bidirectional flexibility from unidirectional charging is mostly constrained by the ability to decrease the load. Depending on the energy intensity of the application, operational strategies that minimize either the power variance or the energy variance are most suitable. We show that, when using the right strategy for a given application, it is possible to provide services reliably without constraining the behavior of electric vehicle users. The versatile overall model enables efficient simulations of large fleets based on representatives. Our sensitivity analysis shows that users are more valuable for flexibility services the more they drive and consume. Lastly, two case studies show that smart electric vehicle charging has a large potential for frequency containment reserve power provision, in particular in synergy with other flexible assets, and for congestion management, in particular for the reduction of feed-in management measures of wind energy in the north of Germany. In conclusion, smart charging of electric vehicles will be a promising flexibility source in future.

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