Smart Charging Solutions for Hybrid and Electric Vehicles. Группа авторов

goal finds a way to reduce the negative impacts mentioned in the previous paragraph. Smart charging has added the functionality of power management and renewable energy integration. The scheduling of the charging and discharging of EVs over the whole day optimizes power exchange between EVs and the utility grid. Peak load demand is met by using EVs as an energy source. Further, renewable energy’s intermittency is curbed by using EVs as energy storage or for charging using renewables. Added benefits of smart charging are the regulation of voltage (by absorbing and supplying reactive power) and frequency (by the exchange of active power), peak shaving and valley filling, and improved utility grid stability [33-35].

      1.3.2 On the Demand Side

The demand side comprises of different types of load: residential, commercial, and industrial. The connected loads are vulnerable to power quality changes. The power quality parameters are defined based on voltage and frequency changes and the harmonics in the power supply [31, 36, 37]. With the integration of renewables and EVs in the system, a balance in the whole power system’s flow is achieved. Balance reduces voltage surges caused due to surplus power during off-peak load hours and uncoordinated addition of renewables or energy storage. Voltage flickers that damage various equipment, especially in the residential sector, are smoothed. The harmonics are reduced with added control and optimization techniques for smart charging. Power flow management and distribution constrains the phase imbalance on the demand side [38, 39]. Thus, consumers’ reliability, on the demand side, is weighted with loads of added benefits from smart charging.

      1.3.3 Overall Infrastructure

      The infrastructure of the existing utility grid is dominated by outdated equipment to monitor and operate. The implementation of smart charging requires robust communication, controller, and fault tracking systems. A possible solution to meet robustness requires using data-rich monitoring systems to perform necessary forecasting and optimization. Another possibility is upgrading the utility grid by replacing current components with smart components. For example, the conventional transformer can be replaced by a smart transformer. Conventional monitoring systems in substations can be replaced with high-performance systems that can perform monitoring, forecasting, and real-time computation of necessary parameters for fault detection, prevention, and correction. Upgrading the utility grid adds a financial burden to the PSO. Further, renewables integration to the utility grid helps reduce capital expenditure spent on increasing generation [40-43], hence, the PSO prefers to add precision sensors, communication systems, and data storage devices to upgrade rather than replacing the components.

      The possibilities of changing infrastructure are immense. Every addition or upgrade to implement smart charging will help make the utility grid infrastructure smart, thereby improving reliability and stability and helping the PSO perform necessary day ahead or month ahead planning to reduce losses, both power and financial.

1.4 Types of Smart Charging

      Smart charging is categorized based on the direction of flow of power: unidirectional or bidirectional. Smart unidirectional charging of EVs is implemented in conjunction with the ToU. EV users are encouraged to charge during off-peak load hours. The implementation of unidirectional smart charging is simple and requires the least technically advanced upgrades of existing components but proves to be effective in reducing uncoordinated charging. Further, the charging rate (slow, medium, or fast) in unidirectional charging is also monitored and controlled.

Bidirectional charging is called a “vehicle to everything” or V2X. The V2X is implemented in two standard configurations (shown in the schematic presented in Figure 1.3).

Figure 1.3 A schematic to differentiate V2H/V2B and V2G.

      1 i. Vehicle to the Building (V2B) or Vehicle to Home (V2H): EV users park EVs in the home, hence, V2B/V2H is prominently used and is a preferred option. The EVs are charged from the supply from the utility grid or a local energy storage device (ESS). The local ESS has energy stored from any renewable energy sources or when the utility grid is in off-peak hours. An additional benefit of V2H/V2B is the use of EV batteries for residential power backup during utility grid outage periods. Further, the simplicity in operation, direct benefits provided to EV users on deploying V2B/V2H, and technology maturity have attracted the market [9, 10, 35, 44].

      2 ii. Vehicle to Grid (V2G): In V2H/V2B, EVs are used as a residential power backup. However, when the EVs are used to provide support to the grid by discharging during peak load hours and charging during off-peak load hours, it is called V2G. V2G renders a noticeable impact on the grid’s operation compared to V2H/V2B [45, 46]. V2G requires intelligent controllers to provide ancillary services such as voltage and frequency control and secondary power reserve. The ToU is also implemented in conjunction with V2G systems [47]. The complexity in the implementation of V2G is higher than V2B/V2H and the technology requires mature and sophisticated solutions to draw market attention.

Table 1.2 Differences between V2B/V2H and V2G systems in smart charging architecture.

Type	Merits	Benefits
V2B/V2H	Simple with least capital investmentLocal control and monitoringEase in scaling and installmentLow power losses and degradation of any power supply equipment	EVs can be used as a backup power supply or a generatorA step to the development of the micro-gridReliability of electricity usageEVs acts as mobile energy storage; local energy deficit can be catered to by moving EVs
V2G	Give an option to EV user to be a partner to PSO and earn by selling electricityFlexibility in operationChance to build infrastructure, which will result in increased reliabilityLarge scale control and managementIf implemented and operated successfully, it promotes EV usage and renewable energy integration	EVs, instead of being a burden to the utility grid, coordinate to reduce the impact of the unprecedented loadImproved voltage and frequency regulationIncreased stability of the gridDemand maturity of technology or sustainable EV market

The difference between different types of smart charging is presented in Table 1.2.

1.5 Entities of a Smart-Charging System

Smart charging systems are evolving. The entities participating in the execution of smart charging algorithms vary based on the countries’ organization structure and policy. For example, in India, power transmission is dominated by the Power System Operation Corporation (POSOCO) under the Ministry of Power and state power distribution subsidiaries take care of the distribution systems. Here, the implementation of smart charging would require the involvement of POSOCO and state power distribution subsidiaries. Based on the works presented in the literature, smart charging entities are listed and briefly explained below.

      1.5.1 Operators: Generation, Transmission, and Distribution

      The power transfer between source and connected loads involves three units of viz.: generation, transmission, and distribution. Smart charging influences all the three units, therefore, they are considered as entities of the system. The addition of EVs as a load to the grid demands more power at the node in which charging