Electric Vehicle Based Battery Storages for Large Scale Wind Power Integration in Denmark

Research output: ResearchPh.D. thesis

Abstract

In the recent years, the electric vehicles (EVs) have drawn great attention world wide as a feasible solution for clean transportation. The electric vehicle technology is not new as it was introduced in the mid 19th century. The low battery capacity, driving range and superior gasoline cars had resulted in the demise of electric cars in the 1930s. However, with the advancement of new high density battery technologies and power electronic converters, it is now viable to produce electric cars of higher efficiency and driving range. The performance and durability of the battery technology is improving on a rapid scale and the battery cost is also reducing which could enable the electric cars to be competitive in the market. The electric vehicles could also benefit the electricity sector in supporting more renewable energy which is also one of the most important driving forces in its promotion. In Denmark, there are many hours of surplus wind power production every year. This could be consumed locally through demand side management of electric vehicles by controlled charging of their batteries. Also, the EV batteries could discharge the stored electricity to the grid on demand, which is collectively termed as the Vehicle-to-Grid (V2G) concept. Thus, the EV storage could operate as a controllable load or distributed generator to minimize the power fluctuations resulting from increased variable wind power. The 2025 Danish Energy Policy plans for fifty per cent wind power production replacing most of the conventional generators. This is not desirable for a reliable and safe power system operation and control. The strategies like wind power regulation or increased cross-border transmission capacity may not be sufficient enough to realize the power system balancing. The former strategy spills the clean wind energy and latter could be expensive and limited as the neighbouring countries are also installing more renewable energy across their borders. One of the other alternative solutions lies with the local distributed storages which could be provided by the flexible, efficient and quick start solutions like the Vehicle-to-Grid systems. They could be aggregated as a large energy storage which could be an attractive alternative to the conventional generator reserves being replaced by the wind power.

The role of electric vehicles as a provider of active power balancing reserve is analysed here as a PhD study, where large amount of wind power are being installed in Denmark. This PhD thesis is organized as different case studies which are analysed as steady state or dynamic simulations on selected wind power dominated Danish power and distribution systems. Some of the worst case scenarios of power system operation, like coincident demand and wind ramp periods, days with high and low wind, reduced power balancing reserves, loss of generation etc. is applied in the case studies. The aggregated models of battery storage representing Vehicle-to-Grid systems, generation units and loads are used in these simulations. A generic model of Vehicle-to-Grid systems which can represent the storage constraints and duration is developed for the use in longterm dynamic simulations. Different control strategies are applied to integrate the Vehicle-to-Grid systems in isolated and interconnected power system operation. The operation strategies of conventional Load Frequency Control and generation models are modified to validate the grid power regulation services from the Vehicle-to-Grid systems. The simulation results from the case studies demonstrate the flexibility of Vehicle-to-Grid systems in operating as a generator or as a load to improve the frequency stability of large wind power integrated distribution networks. It provides smooth, robust and faster power system frequency regulation than the conventional generators in providing active power balancing. This superior performance of the Vehicle-to-Grid systems is also verified for an interconnected power system operation where the power exchange deviations between two control areas are significantly minimised. The extent of electric vehicle penetration in the power distribution systems also depends on the support of smart control strategies to facilitate the safe operation of the power system. This research work shows that the overall operation and control efficiency of power systems can be improved by introducing the Vehicle-to-Grid systems as a future grid regulation ancillary service provider substituting the conventional generation reserves.
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In the recent years, the electric vehicles (EVs) have drawn great attention world wide as a feasible solution for clean transportation. The electric vehicle technology is not new as it was introduced in the mid 19th century. The low battery capacity, driving range and superior gasoline cars had resulted in the demise of electric cars in the 1930s. However, with the advancement of new high density battery technologies and power electronic converters, it is now viable to produce electric cars of higher efficiency and driving range. The performance and durability of the battery technology is improving on a rapid scale and the battery cost is also reducing which could enable the electric cars to be competitive in the market. The electric vehicles could also benefit the electricity sector in supporting more renewable energy which is also one of the most important driving forces in its promotion. In Denmark, there are many hours of surplus wind power production every year. This could be consumed locally through demand side management of electric vehicles by controlled charging of their batteries. Also, the EV batteries could discharge the stored electricity to the grid on demand, which is collectively termed as the Vehicle-to-Grid (V2G) concept. Thus, the EV storage could operate as a controllable load or distributed generator to minimize the power fluctuations resulting from increased variable wind power. The 2025 Danish Energy Policy plans for fifty per cent wind power production replacing most of the conventional generators. This is not desirable for a reliable and safe power system operation and control. The strategies like wind power regulation or increased cross-border transmission capacity may not be sufficient enough to realize the power system balancing. The former strategy spills the clean wind energy and latter could be expensive and limited as the neighbouring countries are also installing more renewable energy across their borders. One of the other alternative solutions lies with the local distributed storages which could be provided by the flexible, efficient and quick start solutions like the Vehicle-to-Grid systems. They could be aggregated as a large energy storage which could be an attractive alternative to the conventional generator reserves being replaced by the wind power.

The role of electric vehicles as a provider of active power balancing reserve is analysed here as a PhD study, where large amount of wind power are being installed in Denmark. This PhD thesis is organized as different case studies which are analysed as steady state or dynamic simulations on selected wind power dominated Danish power and distribution systems. Some of the worst case scenarios of power system operation, like coincident demand and wind ramp periods, days with high and low wind, reduced power balancing reserves, loss of generation etc. is applied in the case studies. The aggregated models of battery storage representing Vehicle-to-Grid systems, generation units and loads are used in these simulations. A generic model of Vehicle-to-Grid systems which can represent the storage constraints and duration is developed for the use in longterm dynamic simulations. Different control strategies are applied to integrate the Vehicle-to-Grid systems in isolated and interconnected power system operation. The operation strategies of conventional Load Frequency Control and generation models are modified to validate the grid power regulation services from the Vehicle-to-Grid systems. The simulation results from the case studies demonstrate the flexibility of Vehicle-to-Grid systems in operating as a generator or as a load to improve the frequency stability of large wind power integrated distribution networks. It provides smooth, robust and faster power system frequency regulation than the conventional generators in providing active power balancing. This superior performance of the Vehicle-to-Grid systems is also verified for an interconnected power system operation where the power exchange deviations between two control areas are significantly minimised. The extent of electric vehicle penetration in the power distribution systems also depends on the support of smart control strategies to facilitate the safe operation of the power system. This research work shows that the overall operation and control efficiency of power systems can be improved by introducing the Vehicle-to-Grid systems as a future grid regulation ancillary service provider substituting the conventional generation reserves.
Original languageEnglish
PublisherDepartment of Energy Technology, Aalborg University
Number of pages190
ISBN (Print)978-87-89179-97-1
StatePublished - 2011
Publication categoryResearch
ID: 47310847