Yutaka Ota

Bio: Yutaka Ota is an academic researcher from Tokyo City University. The author has contributed to research in topics: Electric power system & Electric vehicle. The author has an hindex of 14, co-authored 55 publications receiving 951 citations. Previous affiliations of Yutaka Ota include Murata Manufacturing & University of Tokyo.

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

Abstract: 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.

Novel Dynamic Voltage Support Capability of Photovoltaic Systems for Improvement of Short-Term Voltage Stability in Power Systems

Abstract: The large integration of photovoltaic (PV) power generation systems into power systems causes deterioration in power system stability. In our previous work, we showed that reactive power control using the inverters of PV systems, known as dynamic voltage support (DVS) capability, is a promising approach to improve the short-term voltage stability in power systems. In this paper, we propose a novel DVS capability as a function of PV inverters. In contrast to the conventional DVS capability, the proposed method uses both active and reactive power injection to improve the short-term voltage stability. Numerical examples show that the proposed DVS capability further improves the short-term voltage stability compared with the conventional DVS capability. Furthermore, the proposed method can alleviate a frequency drop after a fault caused by interruption in PV systems.

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

Abstract: 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

Abstract: 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.

A Survey on Demand Response Programs in Smart Grids: Pricing Methods and Optimization Algorithms

Abstract: The smart grid concept continues to evolve and various methods have been developed to enhance the energy efficiency of the electricity infrastructure. Demand Response (DR) is considered as the most cost-effective and reliable solution for the smoothing of the demand curve, when the system is under stress. DR refers to a procedure that is applied to motivate changes in the customers' power consumption habits, in response to incentives regarding the electricity prices. In this paper, we provide a comprehensive review of various DR schemes and programs, based on the motivations offered to the consumers to participate in the program. We classify the proposed DR schemes according to their control mechanism, to the motivations offered to reduce the power consumption and to the DR decision variable. We also present various optimization models for the optimal control of the DR strategies that have been proposed so far. These models are also categorized, based on the target of the optimization procedure. The key aspects that should be considered in the optimization problem are the system's constraints and the computational complexity of the applied optimization algorithm.

Review of the Impact of Vehicle-to-Grid Technologies on Distribution Systems and Utility Interfaces

Abstract: Plug-in vehicles can behave either as loads or as a distributed energy and power resource in a concept known as vehicle-to-grid (V2G) connection. This paper reviews the current status and implementation impact of V2G/grid-to-vehicle (G2V) technologies on distributed systems, requirements, benefits, challenges, and strategies for V2G interfaces of both individual vehicles and fleets. The V2G concept can improve the performance of the electricity grid in areas such as efficiency, stability, and reliability. A V2G-capable vehicle offers reactive power support, active power regulation, tracking of variable renewable energy sources, load balancing, and current harmonic filtering. These technologies can enable ancillary services, such as voltage and frequency control and spinning reserve. Costs of V2G include battery degradation, the need for intensive communication between the vehicles and the grid, effects on grid distribution equipment, infrastructure changes, and social, political, cultural, and technical obstacles. Although V2G operation can reduce the lifetime of vehicle batteries, it is projected to become economical for vehicle owners and grid operators. Components and unidirectional/bidirectional power flow technologies of V2G systems, individual and aggregated structures, and charging/recharging frequency and strategies (uncoordinated/coordinated smart) are addressed. Three elements are required for successful V2G operation: power connection to the grid, control and communication between vehicles and the grid operator, and on-board/off-board intelligent metering. Success of the V2G concept depends on standardization of requirements and infrastructure decisions, battery technology, and efficient and smart scheduling of limited fast-charge infrastructure. A charging/discharging infrastructure must be deployed. Economic benefits of V2G technologies depend on vehicle aggregation and charging/recharging frequency and strategies. The benefits will receive increased attention from grid operators and vehicle owners in the future.

Optimal Scheduling of Vehicle-to-Grid Energy and Ancillary Services

Abstract: Vehicle-to-grid (V2G), the provision of energy and ancillary services from an electric vehicle (EV) to the grid, has the potential to offer financial benefits to EV owners and system benefits to utilities. In this work a V2G algorithm is developed to optimize energy and ancillary services scheduling. The ancillary services considered are load regulation and spinning reserves. The algorithm is developed to be used by an aggregator, which may be a utility or a third party. This algorithm maximizes profits to the aggregator while providing additional system flexibility and peak load shaving to the utility and low costs of EV charging to the customer. The formulation also takes into account unplanned EV departures during the contract periods and compensates accordingly. Simulations using a hypothetical group of 10 000 commuter EVs in the ERCOT system using different battery replacement costs demonstrate these significant benefits.

A review of the development of Smart Grid technologies

Abstract: Energy sustainability and environmental preservation have become worldwide concerns with the many manifestations of climate change and the continually increasing demand for energy. As cities and nations become more technologically advanced, electricity consumption rises to levels that may no longer be manageable if left unattended. The Smart Grid offers an answer to the shift to more sustainable technologies such as distributed generation and microgrids. A general public awareness and adequate attention from potential researchers and policy makers is crucial. This paper presents an overview of the Smart Grid with its general features, functionalities and characteristics. It presents the Smart Grid fundamental and related technologies and have identified the research activities, challenges and issues. It demonstrates how these technologies have shaped the modern electricity grid and continued to evolve and strengthen its role in the better alignment of energy demand and supply. Smart Grid implementation and practices in various locations are also unveiled. Concrete energy policies facilitate Smart Grid initiatives across the nations. Interestingly, Smart Grid practices in different regions barely indicate competition but rather an unbordered community of similar aspirations and shared lessons.