The serious problem of climate change has led the energy sector to modify its generation resources from fuel-based power plants to environmentally friendly renewable resources. However, these green resources are highly intermittent due to weather dependency and they produce increased risks of stability issues in power systems. The deployment of different flexible resources can help the system to become more resilient and secure against uncertainties caused by renewables. Flexible resources can be located at different levels in power systems like, for example, at the transmission-level (TSO), distribution-level (DSO) and customer-level. Each of these levels may have different structures of flexibility trading as well. This paper conducts a comprehensive review from the recent research related to flexible resources at various system levels in smart grids and assesses the trading structures of these resources. Finally, it analyzes the application of a newly emerged ICT technology, blockchain, in the context of flexibility trading.

In smart cities, the end users should play an active role to provide the flexibility services in demand response programmes of smart distribution grids. Moreover, electric vehicles (EVs), their main task being providing green transportation, can play an important role in providing distributed energy in smart cities. In this study, a stochastic problem is presented to manage flexibility of end users and charging operation of EVs in the distribution grid. Thus, the end‐users, aggregators, and EVs are defined as players in the proposed problem. Additionally, three strategies are presented to manage energy centralised, decentralised, or pseudo‐decentralised in the proposed stochastic problem. In the decentralised and pseudo‐decentralised approaches, flexibility of consumers is managed autonomously. On the other hand, EVs are utilised independently by their corresponding owners only in the decentralised approach. Also, a 33‐bus distribution network is considered to assess the performance of the proposed strategies regarding the expected costs of players and the impact of flexibility on transacted energy through aggregators, and the real‐time market. On the basis of simulation results, it is concluded that decentralised strategy to manage energy flexibility and charging operation of EVs by the end users is the win–win strategy for end users and aggregators.