## 4 Discussions  
In the literature, most studies have dealt with the integration of EVs as an alternative energy source in smart grids being applicable and beneficial for a variety of ancillary contributions. In addition, the existing studies explain and detail the role of EVs in smart grid integration. In vehicle-smart grid integration studies, researchers classify system concepts in terms of unidirectional/bidirectional charging and centralized/decentralized scheduling. In addition, the previous studies have classified the concepts, frameworks, benefits, challenges, and optimization methods for the integration of electric vehicles into smart grids. Some studies explain the economic and reliability implications of the vehicle-grid integration sector. Also, on-board/off-board charging infrastructures, challenges for energy storage technologies, and communication requirements for EVs have been presented in the literature. The charge planning, renewable energy integration, and infrastructure facilities of EVs have been clarified with the complexity of charging EVs connected to smart grid technology. Also, the existing studies provide information about the feasibility of a smart V2G system, the interaction of EVs in smart grids, and the integration of sustainable energy resources such as PVs and EVs. The integration of plug-in EVs in smart grids such as vehicle-to-grid (V2G) and grid-to-vehicle (G2V) systems has been another interesting topic for researchers. Some studies present the factors that influence the EV charging load in terms of policy, environment, market, infrastructure, user, and technology. In previous studies, researchers have presented the frameworks, objectives, architectures, benefits, and challenges of the energy management systems of various stakeholders and participants. Also, key analyses of the behaviors of distributed generation and various programs such as demand and response, demand-side management, and power quality management used in energy management systems have been presented. The impacts of EV-grid integration on operating costs and the electricity demand curve for a distribution line with a high penetration of clean energy sources have been examined in previous studies. Studies on the integration of smart grids with EVs seem to focus on some issues. However, the lack of a detailed study describing the power quality impacts and the main contributions of EVs to smart grids is a shortcoming. Therefore, the current work aimed to develop a detailed understanding of the impacts and contributions of EVs on smart grids. Compared to existing review studies, the current study clarified and explained in detail the power system impacts and key contributions of EVs connected to smart grids. With regard to the power system impacts of EVs, the effects on power system stability were first expressed in terms of voltage stability, frequency stability, and oscillation stability. The voltage and current distortions due to EVs connected to the grid were then expressed. This was followed by a discussion of the load profile and power losses associated with the EV-smart grid connection to provide information on the negative impacts. The key contributions of energy management for EV-smart grid integration were identified as load management, supporting renewable energy resources, improving the utilization efficiency of electrical energy generation, improving the system power factor, and energy conservation. Scheduling processes that maintain grid stability and balance power generation and consumption were then detailed for informational purposes. The potential balancing functions of EVs connected to a smart grid were presented as grid quality support. Grid balancing, i.e., the task of the energy supplier to supply the right amount of power to the network of a smart grid, was detailed in the current review. Moreover, socio-economic influences such as emission reduction, new business opportunities, noise reduction, and the green environment were highlighted and clarified as potential benefits.