Читать книгу Smart Charging Solutions for Hybrid and Electric Vehicles - Группа авторов - Страница 20

Uncoordinated and coordinated charging worked on two different objectives. Uncoordinated charging prioritizes the requirements of EV users. In contrast, coordinated charging tries to optimize utility grid operation considering the grid’s requirements and ensuring satisfactory service to the EV users. Although coordinated charging, to some extent, meets the requirement of both the utility grid and EV users, the algorithms and controller developed are inclined to only one segment of operation, the utility grid [9, 26].

The smart charging process, on one hand, lets the EV user decide the priority and, on the other hand, adapts the charging process to meet the requirements of the PSO. For example, suppose a user opts to charge EV during off-peak load hours. In that case, incentives are given in the form of cost reduction in electricity billing. If a user prioritizes to charge rather than considering the grid’s condition, especially during peak-load hours, the electricity billing is higher. The user is not barred from getting the desired service, but an optimal solution is met between the EV owner and the PSO [27]. The smart control ensures the charging of batteries in EVs within a given time and considers PSO constraints, such as voltage and frequency regulations. The smart charging’s prime concern is to reduce the impact of EV charging and enhance grid reliability and stability. For a better understanding, Figure 1.1 shows the list of expected functionalities to define the level of smartness in the charging system.

The platform for electro-mobility (2016) in the European Union (EU) defines smart charging as: “consist[ing] of adapting EV battery charging patterns in response to market signals, such as time-variable electricity prices or incentive payments, or response to acceptance of the consumer’s bid, alone or through aggregation, to sell demand reduction/increase (grid to vehicle) or energy injection (vehicle to grid) in organized electricity markets or for internal portfolio optimization” [26]. Smart charging demands intelligent monitoring, control, and operation [1, 3, 4]. Hence, communication and coordination between the charging infrastructure entities is a must to realize smart charging. In smart charging, the entities are not just a mere power transfer system, but rather a data-rich monitoring system that can monitor, control, coordinate, communicate, forecast, and optimize the operations [2, 7]. A brief description of the various approaches presented in the literature is shown in Figure 1.2.

Figure 1.1 Flow diagram to understand and judge the level of smartness based on functionalities.

Figure 1.2 A brief on different approaches to smart charging techniques.

The definitions and requirements to call a charging infrastructure smart vary, but all the ideas converge to the following goals:

1 i. Guaranteed service to the users as required by optimizing all the entities’ operations and energy management in the system

2 ii. Grid-friendly charging of EVs considering peak shaving; grid-friendly charging of EVs is done when the utility grid has required or surplus power (off-peak hours) after meeting the need of a precedented connected load

3 iii. Renewable integration: the smart charging of EVs should promote the use of renewables. The use of local energy storage systems (ESS) has shown promising results in integrating renewable energy sources to the utility grid. The energy generated from the renewables can be stored in the ESS and supplied to the utility grid when the grid is at stress. EVs act as distributed energy sources by allowing the bidirectional flow of power, hence, EVs can pivot the integration of renewables.

4 iv. Increase reliability and stability: smart charging monitoring and control algorithms should focus on the utility grid’s demand and supply of power. The requirements of all the stakeholders in a power system should be met optimally.

Based on the discussions in the previous paragraphs, a comparison is presented in Table 1.1. Meeting the goals of smart charging is challenging, but its implementation gives an assurance of meeting the specified goals. The impact of smart charging is discussed in the next section.

Table 1.1 A comparison between different types of charging techniques for EVs.

Types of charging	Impact on the grid	Advantages	Disadvantages	Maturity
Uncoordinated	Leads to issues such as increased load demand and change in the shape of load profile, imbalance in phases, and lower power quality	It is user friendly and the deployment does not demand any support services or establishmentThe capital investment cost is the least	Increased power losses in transmission line and componentsVoltage and frequency fluctuationsPhase imbalancePower quality issues such as an increase in total harmonic distortionDegradation of transformers and transmission lines	High (Product readily available in the market and used by consumers)
Coordinated	Reduces negative impact by providing ancillary services and frequency control	Performs peak shaving and demand responseIncreased utilization options to EV users such as providing ancillary services and support to the grid by charging and discharging considering grid conditionsLoad management which reduces power loss and deterioration in the transmission line and transformersOpportunity to engage users in the electricity market	The cooperation of EV users is required, which is uncertainThe incoming and outgoing of EVs is not predictable, hence relying on EVs for ancillary services and regulation can put the power system at riskThe requirement of communication infrastructure will demand huge capital investmentThe assurance of a positive impact on the electricity grid is missing	Medium (pilot project implementation)
Smart	Helps in peak shaving or valley filling, power management on the grid side and energy management on the EV side, ancillary services, voltage and frequency regulation, improvement in power quality, and renewable energy integration	Eases the integration of renewable energy sources in the gridThe use of local energy storage adds flexibility to select power source-grid or energy storage for chargingImproved grid stability and reliabilityControl, operation, management, and monitoring of system at easePromotes usage of EVs due to increased satisfaction of EV owners and PSO	Implementation challenge due to complexityHigher risk operation as the operation and control in the infrastructure are dependent on communication systemsDemand commitment from both EV users and PSOVariability in market operations interferes with the workings of the infrastructure	Low