A Comprehensive Review of Smart Charging Strategies for Electric Vehicles and Way Forward

Uncontrolled and uncoordinated charging of Electric Vehicles (EVs) is producing various challenges in the distribution system, such as network congestion, overloading, and poor voltage profile, that would need grid reinforcement to accommodate EV charging load. However, smart charging of EVs can not only minimize or defer grid upgradation, which is a cost-intensive investment but also help EV stakeholders in optimizing their objectives such as loss minimization for distribution system operator, profit maximization for EV aggregator, charging cost minimization & increased EV users satisfaction. This paper comprehensively reviews the smart charging strategies that address the challenges of uncontrolled EV charging while exploring the opportunities that smart charging can offer to stakeholders. In this paper, EV smart charging strategies are categorized based on different attributes including control topology, methodology, objectives, and electricity pricing. The control topology-based strategies viz., centralized, decentralized, distributed, hierarchical, and local strategies, are analyzed considering different stakeholder objectives, information & decision signal flow, and transactive EV charging scenarios. In this paper, the benefits of electricity pricing-based strategies and transactive smart charging of EVs are investigated. This comprehensive review studies a wide spectrum of various EV smart charging strategies, challenges, opportunities, and future research directions.