Cooperative Optimization of Electric Vehicles and Renewable Energy Resources in a Regional Multi-Microgrid System

By integrating renewable energy sources (RESs) with electric vehicles (EVs) in microgrids, we are able to reduce carbon emissions as well as alleviate the dependence on fossil fuels. In order to improve the economy of an integrated system and fully exploit the potentiality of EVs’ mobile energy storage while achieving a reasonable configuration of RESs, a cooperative optimization method is proposed to cooperatively optimize the economic dispatching and capacity allocation of both RESs and EVs in the context of a regional multi-microgrid system. An across-time-and-space energy transmission (ATSET) of the EVs was considered, and the impact of ATSET of EVs on economic dispatching and capacity allocation of multi-microgrid system was analyzed. In order to overcome the difficulty of finding the global optimum of the non-smooth total cost function, an improved particle swarm optimization (IPSO) algorithm was used to solve the cooperative optimization problem. Case studies were performed, and the simulation results show that the proposed cooperative optimization method can significantly decrease the total cost of a multi-microgrid system

Safe-Commutation Strategy for the Novel Family of Quasi-Z-Source AC-AC Converter

A novel quasi-Z-source ac-ac converter for voltage sag/swell compensation in smart grids is proposed in this paper. Derived from the basic ac-ac safe-commutation mechanism, a new voltage-based commutation strategy is developed, which is achieved without snub circuit and only by sampling the output voltage. Therefore, the control circuit is simplified greatly. Two switches in a one-phase loop are always turned on for current freewheel path in dead time, and current spike and voltage spike are solved well. Compared with conventional ac-ac converters, fewer switches conduct with soft switching during operation, resulting in high efficiency. Then, the proposed converter is analyzed, including the operating modes and voltage ration based on a state-space average. The experimental results validate the theoretical predication well. The safe-commutation strategy can also be easily applied to other converters of the proposed family