**2. Energy management system**

consumption [1]. In Japan, considering that the gasoline price, total annual driving distance, electricity price during night time, and fuel consumption of both gasoline-fueled vehicle and EV are 110 JPY l−1, 10,000 km, 12 JPY kWh−1, and 15 km l−1 and 6 km kWh−1, respectively, the total operational cost of EV may be less than 30% of gasoline-fueled vehicle. Furthermore, the accelerationinthedevelopmentofEValsohasbeeninfluencedstronglybysomevarious factors including fluctuating oil and gas prices, successful advancements in battery technology, and broadersupportinginfrastructure[2,3].Unfortunately,therearestillsomechallengingproblems to expand in a broader scope of the community including high capital cost, long charging time, and relatively short travelable distance [4]. In addition, although the operational cost of EVs is cheaper than the conventional gasoline-fueled vehicles (internal combustion engine–based

To further reduce the initial and operational costs of EV (increase its economic performance), innovative value-added utilization of EV is requested. Furthermore, massive deployment of EVs can disturb significantly the grid electricity, especially when individual charging of EVs in large capacity and number occurred. According to [5], in case that a half of vehicles in Kanto (Tokyo and its surroundings) area are transformed to EVs and half of them are demanding a quick charging simultaneously, about 7.31 GW of additional electricity supply is required. Recently, to give an answer to the above problems, the idea of vehicle-to-grid (V2G) has been

The adoption of EVs to support the electricity of grid or any electricity-related system becomes possible because of controllable charging and discharging behaviors resulting in the possibility of scheduled and coordinated charging and discharging. Therefore, the parked and connected EVs can be assumed as a largely bundled battery which is able to consume (absorb) the electricity from the grid, store it, and release back to the grid. In addition, V2G can be achieved when minimally three fundamental preconditions are totally satisfied: (1) an electricity line connecting both EV and power grid, such as charging station, (2) a communication system transferring the information and control command between EV and grid operator, and (3) an accurate and trusted metering system facilitating fair service measurement [9]. Furthermore, in case that there is any demand for electricity, the grid operators and/or energy management system (EMS) are able to dispatch a control command instructing the connected EVs to discharge their stored electricity to the grid. On the other hand, they can instruct the connected EVs to absorb the electricity due to surplus of electricity or decrease of electricity demand. Therefore, the balance between supply and demand, as well as quality of grid electricity can

V2G provides various possible ancillary services to the electricity grid or any electricity-related system such as load leveling and spinning reserve. In addition, the distributed EVs also can be assumed as a large-scale energy storage (battery) which is potential to be bundled and utilized to minimize the effect of fluctuating supply. As EVs are moving from and to different times and places, they also could be employed as an energy carrier transporting the electricity in different places and times due to some factors such as electricity price difference and emergency condition. From the economic analysis, the massive adoption of EVs to give ancillary service to the grid (V2G) is considered beneficial because the projected profit is still

vehicles), the initial cost of EV is still higher due to high production cost.

proposed and investigated [6–8].

126 Modeling and Simulation for Electric Vehicle Applications

be maintained.

Charging of EVs basically can be categorized into three different capacities: (a) slow charging with capacity lower than 4 kW, (b) fast charging with capacity of 10–20 kW, and (c) ultrafast charging with a maximum capacity of 50 kW or higher [13]. Ultrafast charging is conducted generally under high DC voltage and current. In Japan, this ultrafast charging follows the standard of CHAdeMO (the acronym of "charge de move", equivalent to "move by charge") which offers charging capacity of 10–50 kW. Until the end of 2015, there are about 6000 ultrafast chargers following CHAdeMO standard across Japan [14]. CHAdeMO chargers can facilitate bidirectional electricity flows resulting in possible charging and discharging of EVs. In addition, intelligent controlling system is also generally installed inside the charger, hence high level communication and control can be achieved.

The management of energy, especially the electricity, is usually coordinated and controlled by certain independent operator. In North America, independent system operator (ISO) and regional transmission operator (RTO) act as the independent and neutral organizations that are responsible to coordinate, control, and monitor the electric transmission throughout the state or region [15]. In addition, ISO and independent transmission operator (ITO) were established in Europe which are quite similar with ISO/RTO in North America. The main differences between the US-type ISO/RTO and the EU-type ISO/ITO are the absence of profit motives, and participation and transparency of all the involved stakeholders [16]. ITO in Europe owns the assets and it belongs to certain stakeholders, but has a regulation to guarantee its independence. On the other hand, ISO is fully unbundled operator having no assets although still belongs to certain stakeholders.

In Japan, community energy management system (CEMS) has been proposed and demon‐ strated. The main purpose of CEMS is realizing a resilient and smart community, especially related to efficiency in energy utilization and minimization of CO2 emission. The concept of CEMS comes from the demand to optimize the energy services, maximize the potential economy, and minimize the environmental impacts. CEMS coordinates and monitors all the energy supply and demand throughout the community, hence improving the comfort, security, and safety of the whole community members. In CEMS, the streams of energy and information are flowing simultaneously covering supply, demand, storage, and distribution. As a system, CEMS must be robust and secured because it deals with individual information and its authentication.

**Figure 1.** Basic concept of CEMS.

**Figure 1** shows the basic concept of CEMS. CEMS has an important role of monitoring and controlling all the energy involved in the community. It becomes the core of efficient, secured, and optimized energy utilization throughout the community. CEMS is able to communicate with other entities inside and outside its authority. Inside the community, CEMS communi‐ cates intensively with its lower EMSs such as home energy management system (HEMS), building energy management system (BEMS), and factory energy management system (FEMS). In addition, it also may communicate directly with EVs distributed in the community which are not controlled under certain EMS. CEMS is also able to communicate with other CEMS, large-scale energy providers (utilities), transmission operators, and energy storage operators.

Inside the community, CEMS initially forecasts both energy supply, especially generable renewable energy (RE) and demand. This forecast is usually performed based on historical (for several years before) and meteorological data. Furthermore, it calculates the most opti‐ mized energy balance in terms of quality, security, and economic cost. In case the energy balance between the supply and demand cannot be self-achieved inside the community due to lack of power generation capacity, high and fluctuating demand, and emergency condition, CEMS communicates with other CEMS, utilities, and energy storage providers to deliver or increase their power to the community. On the other hand, in case there is surplus electricity inside the community (due to high supply and/or low demand), CEMS can offer to other CEMS or utilities to buy this surplus electricity.

CEMS is also performing a demand side management (DSM). DSM includes efficient energy usage and demand response (DR) in demand side, instead of adding larger generation capacity at the supply side. DSM can be considered as a dispatchable resource, in which the consumer lower voluntarily their demand, therefore the grid quality can be maintained without any additional power supply.
