Research and simulation of centralized charge and discharge technology of EVs based on MMC

In order to meet the requirements of large-scale EVs (electric vehicles) centralized charge and discharge in a specific situation and solve the resulting serious problem such as three-phase unbalance, high grid-connected harmonic contents and so on, this paper proposes a large-scale centralized charge and discharge system of EVs based on modular multilevel converter (MMC). The topology is based on the traditional MMC, and connects to EVs by bidirectional Buck/Boost circuit in each submodules, which makes bidirectional flow of power between grid and power battery of EVs in submodules. The control strategy of converter level, voltage balance strategy that corresponding to carrier phase shift modulation and Buck/Boost control strategy in submodules are researched, and the power quality problems caused by large-scale charge and discharge is avoided. The simulation based on Matlab/Simulink verifies feasibility of the system structure and the effectiveness of the control strategy.