To make up for the shortcomings of one-way energy flow between electric vehicles (EVs) and the grid, improve the flexibility of EVs in the charging and discharging process and strengthen the capability to absorb new energy generation on-site, a DC microgrid topology with bidirectional wireless power transmission (BD-WPT) for EVs is proposed, and a control method of using the EV battery as a mobile energy storage device is studied. This topology is based on a wind-solar hybrid power generation system and hybrid energy storage, and a power-based control method for the BD-WPT system is put forward, which can ensure that the EV can be used both as a load to absorb energy and as an energy storage device to emit energy. To guarantee the stable operation of the system, a microgrid upper-layer central controller is further designed. Simulink simulation results show that the energy interaction between EVs and the grid improves the stability of grid operation, and the BD-WPT system can improve the charging and discharging effects of EVs. To a certain extent, the on-site consumption of new energy power generation is promoted, indicating the effectiveness of the proposed topology and the superiority of the control strategy.

在局部遮荫下，针对传统最大功率跟踪MPPT（maximum power point tracking）算法不能跳出局部最优找到全局最大功率，及传统蝴蝶优化算法BOA（butterfly optimization algorithm）存在搜索震荡大和收敛慢等问题，提出一种新型的MPPT控制算法。该算法在传统蝴蝶算法上加入收敛因子，来加快全局搜索速度；引入自适应权重系数，来提高蝴蝶优化算法在局部搜索的搜索速度及追踪精度等性能。通过仿真，对比混合算法（INBOA）与BOA、粒子群优化PSO（particle swarm optimization）算法、灰狼优化算法GWO（gray wolf optimization）的函数收敛曲线，验证所提算法具有收敛速度快、搜索精度高的优点；对比INBOA、BOA、PSO、GWO的MPPT算法在静态与动态环境下的性能指标可知，INBOA的MPPT算法具有更高追踪效率、更快收敛速度以及更小的搜索震荡。从而进一步验证混合算法的优越性。

A 65 kWh liquid-cooled power battery system for a pure electric commercial vehicle was taken as the research object, and a thermal management test bench was independently designed and built, focusing on the comparison of cooling effect of the thermal management system on battery temperature under different ambient temperatures and working conditions. It was found that although the thermal management system can control the battery temperature to be within an appropriate range, the energy consumption in a high-temperature environment was higher. Therefore, the thermal management control strategy was optimized. The optimized control strategies were superior to the original control strategy in terms of battery cooling effects and energy consumption, and the energy was saved by 37.78% and 78.63% under high-temperature high-speed working condition and comprehensive urban working condition, respectively, indicating that the energy efficiency of thermal management was significantly improved.

A three-level dual active bridge (3L-DAB) DC-DC converter with the introduction of 3L legs is applied to the bidirectional charging stack in a charging station, so that the system’s regulating flexibility can be enhanced by adding another control degree of freedom. When the conventional phase shift (CPS) control is adopted, the current stress of the 3L-DAB converter is relatively large, which increases the loss and thus reduces the system efficiency. To address this issue, an optimal control strategy is proposed to minimize the current stress of the DC-DC converter applied to the bidirectional charging stack. First, the mathematical model of the 3L-DAB converter under phase shift control is established to analyze the relationship between the harmonics of inductance current RMS and the control degrees of freedom. On this basis, a control strategy based on fundamental wave optimization is put forward to reduce the inductance current of the converter. Finally, the correctness of theoretical analysis and the effectiveness of the proposed control strategy are verified by comparing the simulation and experimental results among the proposed optimal control and other control methods.