Читать книгу Smart Charging Solutions for Hybrid and Electric Vehicles - Группа авторов - Страница 25

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.