In recent years, urban rail systems have developed drastically. In these systems, when induction electrical machine suddenly brakes, a great package of energy is produced. This package of energy can be stored in energy storage devices such as battery, ultra-capacitor and flywheel. In this paper, an electrical topology is proposed to absorb regenerative braking energy and to store it in ultracapacitor and battery. Ultra-capacitor can to deliver the stored energy to DC grid and to charge the battery for auxiliary applications such as lighting and cooling systems. The proposed system is modeled based on large signal averaged modeling, which leads to the simplicity of calculations. The control system is based on Lyapunov stability theorem which guarantees system stability. Also, an energy management algorithm is proposed to control energy under braking and steady-state conditions. Finally, the simulation results validate the effectiveness of the proposed control and energy management system.

At recent years, using hybrid energy storage systems has become a global solution to supply continuous, reliable and clean energy to power electronic devices. By using these technologies, many advantages of energy storage systems can be combined properly and an adequate energy supply for specific applications is achievable. In today's world, there is a continuous global need for more energy which, at the same time, has to be cleaner than the energy produced from the traditional generation technologies. This need has facilitated the increasing penetration of distributed generation technologies and primarily of renewable energy sources. In addition, by maturating renewable energy sources and technologies around it, providing a significant part of the total energy generation, requiring fewer costs with cleaner characteristics for environment, has become possible. The extensive use of such energy sources in today's electricity networks can indisputably minimize the threat of global warming and climate change. There are many advantages in using renewable energy sources alongside with the energy generated by fossil fuels which is discussed in this article. This work also discusses different types of energy storage devices and studies the advantages and disadvantages of these devices. Then different types of renewable energy sources and their role in in hybrid energy systems will be analyzed and noted. Some energy storage systems are modeled and simulated. Required power electronic circuits in hybrid storage systems will be introduced. At the end, some practical examples of hybrid energy systems (such as Battery-Supercapacitor) are presented, modeled and simulated.

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Electric vehicles are becoming increasingly popular in societies and an important part of smart grids. Utility companies should be able to provide them with vital energy as they need electric energy instead of fuel, and this is where new challenges emerge in the network. In order to avoid causing utilities to incur additional energy and economic losses, researchers have proposed smart charging as a way to provide adequate energy to vehicles. When developing a charging schedule for a fleet of EVs, special considerations are made on variables such as energy, cost, and EVs milage. In this review paper, the importance of EVs integration into smart grids is studied, and then different methods to develop EVs charging scheduling are investigated. These methods can vary from optimization algorithms to learning-based, and game theory-based approaches. Then, as the considered system consists of three main actors, including EV users, the utility operator, and aggregators, a systematic review is conducted on these actors, and objectives related to each one are analyzed. Finally, research gaps related to the problem are studied. Researchers can use this review to conduct further research on the integration of EVs into smart grids.

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