Jayakrishnan Radhakrishna Pillai

Integration of Vehicle-to-Grid in the Western Danish Power System

The Danish power system is characterized by a large penetration of wind power. As the nature of the wind power is unpredictable, more balancing power is desired for a stable and reliable operation of the power system. The present balancing power in Denmark is provided mostly by the large central power plants followed by a number of decentralized combined heat and power units and connections from abroad. The future energy plans in Denmark aim for 50% wind power capacity integration which will replace many conventional large power plant units. The limited control and regulation power capabilities of large power plants in the future demands for new balancing solutions like vehicle-to-grid (V2G) systems. In this paper, aggregated electric vehicle (EV)-based battery storage representing a V2G system is modeled for the use in long-term dynamic power system simulations. Further, it is analyzed for power system regulation services for typical days with high and low wind production in the Western Danish power system. The results show that the regulation needs from conventional generators and the power deviations between West Denmark and Union for the Coordination of Electricity Transmission (UCTE) control areas are significantly minimized by the faster up and down regulation characteristics of the EV battery storage.

Impacts of electric vehicle loads on power distribution systems

Electric vehicles (EVs) are the most promising alternative to replace a significant amount of gasoline vehicles to provide cleaner, CO2 free and climate friendly transportation. On integrating more electric vehicles, the electric utilities must analyse the related impacts on the electricity system operation. This paper investigates the effects on the key power distribution system parameters like voltages, line drops, system losses etc. by integrating electric vehicles in the range of 0-50% of the cars with different charging capacities. The dump as well as smart charging modes of electric vehicles is applied in this analysis. A typical Danish primary power distribution system is used as a test case for the studies. From the simulation results, not more than 10% of electric vehicles could be integrated in the test system for the dump charging mode. About 40% of electric vehicle loads could be accommodated in the network with the smart charging mode. The extent of integrating EVs in an area is constrained by the EV charging behavior and the safe operational limits of electricity system parameters.

Optimizing Electric Vehicle Coordination Over a Heterogeneous Mesh Network in a Scaled-Down Smart Grid Testbed

High penetration of renewable energy sources and electric vehicles (EVs) create power imbalance and congestion in the existing power network, and hence causes significant problems in the control and operation. Despite investing huge efforts from the electric utilities, governments, and researchers, smart grid (SG) is still at the developmental stage to address those issues. In this regard, a smart grid testbed (SGT) is desirable to develop, analyze, and demonstrate various novel SG solutions, namely demand response, real-time pricing, and congestion management. In this paper, a novel SGT is developed in a laboratory by scaling a 250 kVA, 0.4 kV real low-voltage distribution feeder down to 1 kVA, 0.22 kV. Information and communication technology is integrated in the scaled-down network to establish real-time monitoring and control. The novelty of the developed testbed is demonstrated by optimizing EV charging coordination realized through the synchronized exchange of monitoring and control packets via an heterogeneous Ethernet-based mesh network.

Vehicle-to-Grid for islanded power system operation in Bornholm

Vehicle-to-Grid (V2G) systems are an emerging concept of utilizing the battery storage of electric vehicles (EVs) for providing power system regulation services. This technology could be used to balance the variable electricity generated from various renewable energy sources. This article considers a model of an aggregated electric vehicle based battery storage to support an isolated power system operating with a large wind power penetration in the Danish island of Bornholm. From the simulation results, the EV battery storages represented by the V2G systems are able to integrate more fluctuating wind power. The islanded Bornholm power system operates satisfactory for the case of replacing most of the conventional generator reserves with V2G systems, which may represent a future operation scenario.

Integration of Electric Vehicles in low voltage Danish distribution grids

Electric Vehicles (EVs) are considered as one of the important components of the future intelligent grids. Their role as energy storages in the electricity grid could provide local sustainable solutions to support more renewable energy. In order to estimate the extent of interaction of EVs in the electricity grid operation, a careful examination in the local electricity system is essential. This paper investigates the degree of EV penetration and its key influence on the low voltage distribution grids. Three detailed models of residential grids in Denmark are considered as test cases in this study, where alternate and flexible domestic solutions like EVs are inevitable for integrating the increasing amount of variable wind power. The result from these analyses shows that the individual feeder capabilities of handling an increasing amount of EV loads, is varied from 0-40% on an hourly basis. Also it is shown that there is enough head-space on the transformer capacity which can be used to charge many EVs during a day. The overall transformer capability of handling EV loads varies between 6-40% for peak and minimum demand hours, which is dependent on the robustness of the grids. The voltage drops are reflected as the major technical constraint to the stable operation of the electricity grids for integrating more EVs, when compared to the thermal loading on the cables.

Vehicle-to-grid systems for frequency regulation in an Islanded Danish distribution network

Electric vehicles (EVs) have gained significant attention in the recent years due to their prospects in reducing green-house gas emissions benefitting the transportation sector directly and the electricity sector indirectly. Vehicle-to-grid (V2G) systems using the battery storages of electric vehicles could provide power system ancillary services in the form of power balancing reserves to support the large-scale integration of variable renewable energy sources like wind power. This paper investigates the dynamic frequency response of an islanded Danish distribution system operation with large amount of wind power supported by the Vehicle-to-grid systems. The power system simulations are analysed for scenarios with 48% and 65% of wind power penetration. The simulation results show that the V2G systems provide a faster and stable frequency control than the conventional generation units. V2G systems can be considered as a flexible solution for frequency regulation in future electric power systems.

Flexible Demand Control to Enhance the Dynamic Operation of Low Voltage Networks

Moving toward a carbon free energy system has become an objective for many countries nowadays. Among other changes, the electrification of strategic sectors, such as heating and transportation, is inevitable. As a consequence, the current power system load will substantially increase. In this context, the nature of the expected loads (heat pumps, plug-in electric vehicles, etc.) makes the low voltage (LV) networks specially targeted. A promising solution to overcome the challenges resulting from their grid integration is demand response (DR). This paper introduces a hierarchical structure for controlling the DR of a LV grid. This is designed to maximize the grid utilization, thereby reducing the need for reinforcement; accommodate the maximum number of flexible loads; and satisfy the power and comfort requirements from each of the consumers in the network. The validation of the proposed concept is made using a model of an LV network currently operative in Denmark. The results show that by using the proposed strategy a considerable improvement of the minimum system voltage and a better load distribution is obtained.

Demand flexibility from residential heat pump

Demand response (DR) is considered as a potentially effective tool to compensate generation intermittency imposed by renewable sources. Further, DR can instigate to offer optimum asset utilization and to avoid or delay the need for new infrastructure investment. Being a sizable load together with high thermal time constant, heat pumps (HP) can offer a great deal of flexibility in the future intelligent grids especially to compensate fluctuating generation. However, the HP flexibility is highly dependent on thermal demand profile, namely hot water and space heating demand. This paper proposes price based scheduling followed by a demand dispatch based central control and a local voltage based adaptive control, to realize HP demand flexibility. Two-step control architecture, namely local primary control encompassed by the central coordinative control, is proposed to implement the aforementioned control techniques. Results show that HP flexibility can contribute significantly to both the local network and system level balancing.

Hierarchical control architecture for demand response in smart grids

To compensate for intermittency of generation and consequent impacts of non-dispatchable generating sources, especially solar PV panels and wind turbines, demand response (DR) has been considered one of the most effective tools. In recent years, DR has received more attention as a potentially effective tool for optimum asset utilization and to avoid or delay the need for new infrastructure investment. Furthermore, most of the power networks are under the process of reconfiguration to realize the concept of smart grid and are at the transforming stage to support various forms of DR. However, a number of issues, including DR enabling technologies, control strategy, and control architecture, are still under discussion. This paper outlines novel control requirements based on the categorization of existing DR techniques. More specifically, the roles and responsibilities of smart grid actors for every DR category are allotted and their mode of interactions to coordinate individual as well as coordinative goals is described. Next, hierarchical control architecture (HCA) is developed for the overall coordination of control strategies for individual DR categories. The involved issues are discussed and compared.

Electric vehicles in low voltage residential grid: A danish case study

Electric Vehicles (EVs) have gained large interest in the energy sector as a carrier to support clean transportation and green electricity. The potential to use battery storages of electric vehicles as a sink for excess electricity that may result from large integration of wind power, especially in countries like Denmark, is widely discussed and promoted. However, the wide-spread adoption of EVs requires the provision of intelligent grid and EV charging infrastructure. To analyse and understand the amount of EVs that could be integrated in the local distribution grids, within its existing capabilities, is absolutely essential for the system operators to plan and implement the levels of grid reinforcement and intelligence required. This paper investigates the local grid limitations to accommodate large amount of EVs of sizable power ratings in residential areas. The case study applied in this paper uses a detailed secondary distribution grid model in Denmark. Various EV integration scenarios are analysed in this work to understand the network operational flexibility and ruggedness. The simulation results show that level of EV integration varies with the strength of different feeders in the studied network. Simple grid reinforcement measures like adding new feeders in the existing network improves EV penetration levels.