Kithsiri M. Liyanage

Autonomous Distributed V2G (Vehicle-to-Grid) Satisfying Scheduled Charging

To integrate large scale renewable energy sources in the power grid, the battery energy storage performs an important role for smoothing their natural intermittency and ensuring grid-wide frequency stability. Electric vehicles have not only large introduction potential but also much available time for control because they are almost plugged in the home outlets as distributed battery energy storages. Therefore, vehicle-to-grid (V2G) is expected to be one of the key technologies in smart grid strategies. This paper proposes an autonomous distributed V2G control scheme. A grid-connected electric vehicle supplies a distributed spinning reserve according to the frequency deviation at the plug-in terminal, which is a signal of supply and demand imbalance in the power grid. As a style of EV utilization, it is assumed that vehicle use set next plug-out timing in advance. In such assumption, user convenience is satisfied by performing a scheduled charging for the plug-out, and plug-in idle time is available for the V2G control. Therefore a smart charging control is considered in the proposed scheme. Satisfaction of vehicle user convenience and effect to the load frequency control is evaluated through a simulation by using a typical two area interconnected power grid model and an automotive lithium-ion battery model.

Smart Grid: Technology and Applications

Electric power systems worldwide face radical transformation with the need to decarbonise electricity supply, replace ageing assets and harness new information and communication technologies (ICT). The Smart Grid uses advanced ICT to control next generation power systems reliably and efficiently. This authoritative guide demonstrates the importance of the Smart Grid and shows how ICT will extend beyond transmission voltages to distribution networks and customer-level operation through Smart Meters and Smart Homes. Smart Grid Technology and Applications: * Clearly unravels the evolving Smart Grid concept with extensive illustrations and practical examples. * Describes the spectrum of key enabling technologies required for the realisation of the Smart Grid with worked examples to illustrate the applications. * Enables readers to engage with the immediate development of the power system and take part in the debate over the future Smart Grid. * Introduces the constituent topics from first principles, assuming only a basic knowledge of mathematics, circuits and power systems. * Brings together the expertise of a highly experienced and international author team from the UK, Sri Lanka, China and Japan. Electrical, electronics and computer engineering researchers, practitioners and consultants working in inter-disciplinary Smart Grid RD&D will significantly enhance their knowledge through this reference. The tutorial style will greatly benefit final year undergraduate and masters students as the curriculum increasing focuses on the breadth of technologies that contribute to Smart Grid realisation.

Autonomous distributed V2G (vehicle-to-grid) considering charging request and battery condition

Integration of large scale renewable energy sources into power grid, battery energy storage performs an important role for smoothing their natural intermittency and ensuring grid-wide frequency stability. Plug-in hybrid electric vehicle and electric vehicle have potential of alternative of the battery because of its high performance lithiumion battery and longer plug-in time than driving time. Therefore, vehicle-to-grid is expected to be one of the key technologies for smart grids integrating renewable energy sources. In this paper, an autonomous distributed vehicle-to-grid control scheme is proposed. Grid-connected electric vehicles contribute frequency regulation and spinning reserve triggered by self-terminal frequency, which is a signal of supply and demand balance in the power grid. Proposed scheme also consider charging request for the next drive and battery condition during the vehicle-to-grid. Satisfaction of vehicle user convenience and effect load frequency control is evaluated through coupled analysis of vehicle-to-grid model and typical power grid model.

An autonomous distributed vehicle-to-grid control of grid-connected electric vehicle

Penetrating large amount of renewable energy resources into power system, battery energy storage system perform important role for smoothing their natural variability, ensuring grid-wide frequency stability, and suppressing voltage rise caused by reverse power flow. The ubiquitous power grid concept has been proposed as a Japanese smart grid, in where total battery capacity could be optimized by coordinating controllable distributed generators, loads on demand side, for example, heat pump system with heat storage, and plug-in hybrid vehicle or battery electric vehicle with onboard battery. In this paper, we propose a vehicle-to-grid control of grid-connected plug-in hybrid electric vehicle and electric vehicle as a kind of the demand response in the ubiquitous power grid. Proposed control is based on simple droop characteristics against the power system frequency at plug-in terminal, and considers the risks about use for vehicle and battery condition. Autonomous distributed Smart Storage for governor free control, spinning reserve, local area voltage control, and other smart grid applications is realized by packaging the proposed control to automotive power electronics circuit and electric control unit.

Effect of autonomous distributed vehicle-to-grid (V2G) on power system frequency control

Penetrating large amount of renewable energy sources into power system, battery energy storage performs an important role for smoothing their natural intermittency, ensuring grid-wide frequency stability, and suppressing voltage rise caused by reverse power flow. The ubiquitous power grid is one of the concepts as a smart grid in Japanese context, where the total battery capacity can be optimized by coordinating renewable energy sources, controllable distributed generators, and controllable loads on demand side, for example, heat pump based water heater with heat storage, and plug-in hybrid vehicle or electric vehicle with onboard battery, and so on. These controllable devices behave as an autonomous distributed smart storage by charging or discharging against the power system frequency measurement as paying attention to user convenience. In this paper, effects of the autonomous distributed smart storage on bulk power systems are investigated thorough a load frequency control simulation.

Impacts of Communication Delay on the Performance of a Control Scheme to Minimize Power Fluctuations Introduced by Renewable Generation under Varying V2G Vehicle Pool Size

The power outputs of non-conventional renewable sources are random and intermittent in nature. The integration of such sources in large numbers into existing power networks in the future could make the reliable and stable operation of power systems highly challenging. In this paper, the performance of a method based on balancing active power near real time, to reduce power fluctuations produced by renewable sources, is presented. The ability to exchange timely information and availability of adequate energy storage capacity are vital factors that determine the effectiveness of this method. Hence the performance, under varying communication delay and V2G vehicle pool size, of this method was evaluated by the authors. Three indices were defined and used to measure performance. The frequency of power balancing process was also varied during the study to accommodate longer information exchange delays. Results reveal that performance improves as communication delay and the period of control cycle are shortened. It was also observed that beyond a certain size of V2G pool, performance improvement reaches saturation. This indicates that, for a given system, there is a minimum V2G pool size requirement for studied method to deliver peak performance.

Autonomous Distributed Vehicle-to-Grid for Ubiquitous Power Grid and its Effect as a Spinning Reserve

This paper propose an autonomous distributed vehicle-to-grid control scheme of grid-connected (plug-in hybrid) electric vehicle. Grid-friendly charge and discharge maintaining user convenience for plug-out and battery state-of-charge is realized based on frequency measurement at the plug-in terminal. Implementing proposed scheme to automotive power electronics circuit, (plug-in hybrid) electric vehicle works as a smart storage which is an alternative to stationary battery. The smart storage is expected to be a spinning reserve because of its high-speed response without information exchange to a central load dispatch center. An effect of the autonomous distributed vehicle-to-grid and cooperation with centralized speed governor control and load frequency control of conventional thermal power generator is evaluated.

Optimal Placement and Control of BESS for a Distribution System Integrated with PV systems

Recently, photovoltaic generation (PV) has attracted a great attention as one of green power generations. Accordingly a large amount of PV systems will be installed in residential areas in the coming years. In such scenario, reverse power flow caused by PV in feeders may cause some problems such as voltage rise over upper limits in the distribution line, and the reverse power flow into the distribution substation. Battery energy storage system (BESS) is a promising option to solve the above both problems at the same time. However, the effect of BESS depends on location of BESS. Therefore, it is necessary to consider an appropriate location in the residential distribution system to install BESS to obtain an optimal effect. This paper investigates an optimal placement pattern of BESS in the residential distribution system with certain patterns of PV installation. It has been made clear that the obtained results can determine the best placement pattern of BESS with the minimum required BESS capacity and power loss.

Coordinated control of elements in Ubiquitous Power Networks to support Load Frequency Control

Within the carbon constrained world, virtually unrestricted integration of renewable energy sources into power networks is expected to become common in practice, making power systems to be more ubiquitous[1] in nature, structurally and operationally. Consequently, handling the intermittent and random behavior of renewable generation, thus Load Frequency Control (LFC), would become one of the major challenges in power systems operations in the future. In this paper we report a simple method that can support LFC of Ubiquitous Power Networks, rich in renewable generation. In the proposed method, frequency control support is achieved through the coordinated control of active power produced and consumed by various controllable system elements at distribution level where renewable generation is expected to appear in large scale. Simulation results obtained for a test system are also presented to demonstrate the effectiveness of proposed method.

Evaluating the impact of battery energy storage systems capacity on the performance of coordinated control of elements in ubiquitous power networks

Within a carbon constrained world, the proportion of generation from nonconventional renewable energy sources in the generation mix of power systems, is expected to increase substantially. The generation from renewable sources, connected to power networks mostly at distribution level, will change the traditional power flow patterns and produce adverse power fluctuations due to its random nature. Although battery energy storage systems (BESS) can be employed to reduce power fluctuations, economic constraints imposed by the high cost of them justifies, under certain conditions, converting only a portion of available renewable energy to electricity and allowing the balance to go waste[1,2], an undesirable proposition from environmental standpoint. In this back drop, a strategy, based on the coordinated control of system elements, requiring lower BESS capacity and capable of reducing renewable energy waste, to control power fluctuations is presented and its performances under different BESS capacities and operating conditions were studied and reported in this paper. Numerical simulation carried out revealed the presence of a performance saturation linked to increasing BESS capacity. Reaching the saturation at BESS capacities, MW and MWhr, much smaller than power and energy associated with fluctuating generation, demonstrates the ability of proposed algorithm to control power fluctuations efficiently. The saturation effect further suggests that the accurate estimation of capacity requirement is necessary to obtain better cost performances from BESSs.