Steffen Schlegel

Utilizing battery electric and plug-in hybrids for smart grid operation techniques

E-Mobility provides a wide potential for diversification of traffic sectors primary energy source. Until now petrol could be seen as the dominating one. The rollout of battery electric vehicles — plug-in-hybrids included — can be supplied by wind, solar, water, and coal and nuclear as the primary energy source. Obviously the rollout is strictly connected to the issue of grid capability to the additional electric load. First investigations show a concentration of charging in the noon and evening hours, which is coincident with common grid load. As a matter of fact there will be an overload on distribution grid devices and voltage dip, especially on low voltages cables, transformers and mid voltage cables. The rate of overload and voltage dip is hardly connected to the amount of supplied electric vehicles as well as to grid topology and galvanic distance between charge points. The following work deals in modeling and optimization basics of the expected electric load “EV” for simulation purposes. An especial architecture for managing EVs with special respect to the German liberalized market will be shown.

On the Optimization of the Load of Electric Vehicles

Abstract E-Mobility provides a wide potential for diversification of traffic sectors primary energy source. Until now petrol could be seen as the dominating one. The rollout of battery electric vehicles -plug-in-hybrids included – can be supplied by wind, solar, water, and coal and nuclear as the primary energy source. Mobility of tomorrow could be fully made in Germany. Obviously the rollout is strictly connected to the issue of grid capability to the additional electric load. First investigations show a concentration of charging in the noon and evening hours, which is coincident with common grid load. As a matter of fact there will be an overload on distribution grid devices, especially on low voltages cables, transformers and mid voltage cables. The rate of overload is hardly connected to the amount of supplied electric vehicles as well as to grid topology and galvanic distance between charge points. The following work deals in modelling and optimization of the expected electric load “EV”.

Einfluss Gesteuerten Ladens von Elektrofahrzeugen auf Verteilnetze bei volatiler Windeinspeisung

Zusammenfassung Der vorliegende Aufsatz fasst Erkenntnisse zum Gesteuerten Laden von Elektrofahrzeugen zusammen. Es werden zwei Verfahren gezeigt. Das Wind−2-Vehicle-Verfahren (W2V) ist Beispiel für die Nutzung Gesteuerten Ladens, um einer regenerativen Einspeisung folgenden Bedarf zu realisieren. Das Lokale Lastmanagement (LLM) ist Beispiel, um Informationen aus dem Verteilnetz zu nutzen, um die Ladeleistung von Elektrofahrzeugen zeitlich zu begrenzen. Abstract This work summarizes findings obtained from controlled charging of Electric Vehicles. Two approaches will be explained. The Wind−2-Vehicle method (W2V) is an example for using controlled EV charging in order to create a renewable supply following demand. The Local Load Management (LLM) method is an example for using information from distribution grids to limit the charging power of Electric Vehicles over time.

Approach for load frequency control participation by decentralized energy devices

Global trends of worldwide increasing energy demand, growing scarcity of fossil resources and increasing awareness of environment especially CO2 emissions require a rethinking of todays electrical power system. Thus, sustainable electric power generation, whose transmission and distribution gains more and more attention. Hence, a steadily increasing level of renewable energies is noticeable, which are predominantly connected to the medium and low voltage levels. At the same time, declining profitability and climate policy objectives are leading to gradual shutdown of conventional power plants. Because of those changes, todays operation concepts and system responsibility policies have to be adjusted. The challenge is how to compensate the loss of controllable power generation especially in times of needed ancillary services like load frequency control. This paper outlines an approach for load frequency control participation by decentralized energy devices exemplarily for electric vehicles in Germany while taking the DSO objectives into account. The simulation shows that ancillary services can be provided from the DSOs levels without endangering DSO system security.

Involvement of flexible loads in transmission system operation

A secure electric power supply is fundamental for todays living standard and the economic development of any country. Regarding global trends in the future, electric power generation has to be sustainable and will consequently not be based on fossil resources. This leads to a strengthened expansion of renewable energy generation (REG), in particular in Germany. The corresponding infeed with volatile character presents a major challenge to system operators. Nowadays transmission system operators (TSO) in Germany are increasingly forced to apply emergency measures to ensure system security. This paper outlines two approaches on how controllable (flexible) loads can be utilized to support the grid operation of a TSO. Their impact will be demonstrated on the basis of numerical case studies.

Closed loop flow detection in power systems based on Floyd-Warshall algorithm

The European transmission system operators of today have to struggle with a general increase in power flows, leading more and more to line congestions in certain transmission corridors. One reasonable countermeasure for this is active power flow control using power flow controlling devices (PFCD) like phase shifting transformers (PST) or Flexible AC Transmission Systems (FACTS). To avoid negative interdependencies between these utilities in different European control areas, the need for coordination of these PFCDs is expected to rise. During these coordination it is important to avoid the occurrence of closed loop flows after PFCD adaptation. Closed loop flows are circulated active power flows, which increase the grid losses. This paper proposes to use the shortest path method from Floyd-Warshall algorithm and adapt it for the detection of closed loop flows in power systems. The method is tested on standard IEEE test systems.

Approach for N-1 secure grid operation with 100% renewables

The aim of a future electric power generation without CO2 emissions requires a rethinking of todays electrical power system. One important aspect is renewable energy sources. Thereby, wind power and photovoltaic units have the biggest growth rates, even though there generated power is volatile and do not correlate to the actual load situation. As a consequence of weather conditions, the generation shifts temporally as well as geographically and makes the secure system operation more difficult. This paper presents a concept for an electrical power system supply based on 100% renewables using a vertical system operation approach to meet these effects. Therefore, the technical challenges of such a system configuration are analyzed. It is shown, that the vertical system operation approach has a positive effect on the N-1 security.

Techno-economic evaluation of electric vehicles as flexible load for providing grid services

System operators use grid services to ensure grid stability and security. In liberalized energy markets, these services are made available through market tenders. Flexible generation and load representing a major part of these grid services. This paper presents the development of a Key Performance Indicator (KPI) based methodology and the evaluation undertaken during the field trial for the project sMobiliTy. The KPIs are developed and benchmarked by deriving generalized requirements through a wide range of grid services in multiple networks. The approach is used to assess and quantify the suitability of electric vehicle pools with respect to technical and market tendering requirements as well as network connection requirements for distributed devices.

Design of a simulation model to analyze the consequences of using electric vehicles to provide control reserve

Enactment of stringent climate protection directives and policies for renewable energy as well as electric vehicle integration is expected to place considerable strain on system frequency stability. Decreasing share of conventional power plants and consequently the loss of readily controllable power generation, makes controlled charging of electric vehicles an attractive option for the Transmission System Operators (TSO). In order to analyze the capabilities of electric vehicles to provide frequency control to the TSO, this paper outlines a simulation model of power system, which includes a model of electric vehicles based on real measurement data. Thereby, the complete communication path from TSO to aggregator and then to electric vehicles is modeled, with communication delays as well as electric vehicle (EV) and control zone specific parameters. The model is tested and validated using the UCTE reference case.

Investigation of the impact of electric vehicles on the German market for control reserve

The opening of the market for control reserve for new technologies enables the integration of electric vehicles (EVs) into this market and to generate potential revenue for the car owner. The intent of this paper is to investigate the impact of EVs and their additional bids on the German market for control reserve. This paper investigates the influence of the variation of bids in context of cost and revenues and identifies the amount of balancing energy that is provided by different bids normalized to a single EV. This happens with the aim of a model which contains, within the framework of the current design of the market for control reserve, a synthetic demand signal for negative secondary control reserve (SCR), a data set with real tender information and fictitious bids. As result, the paper presents bid variations, which leading to attractive revenues and provide an incentive to participate in the German market for control re-serves.