Research On Switching Control Method Of Multi Port Energy Router Based On Solid State Transformer

As the core of energy interconnection,electric energy router can not only realize the energy exchange between different voltage levels,but also realize the plug and play of renewable energy at its port.The power router can monitor and distribute the power flow of the microgrid,so as to ensure the stability of the system.The topology and control strategy of power router based on solid-state transformer are analyzed and studied.In this paper,three-stage solid-state transformer is adopted,and each stage converter uses modular structure,which improves the scalability of power router.Compared with the traditional control method,the switching control is closer to the working mode of power electronic circuit.According to the function,the three-level power router can be divided into three levels:network level,link level and user level.This paper analyzes the topology and switching mode combination of all levels,and obtains the equivalent simplified circuit of all levels.By analyzing the topology of network level,link level and user level,the switching state combination is described by switching function,the switching system model is obtained,and the switching control strategy is obtained according to its function.Phase shift control is adopted in the link level,and the changes of output voltage and current after the working state switching of the converter are analyzed;The user level uses non positive sequence voltage compensation control,which can effectively solve the three-phase imbalance problem of user level.According to the characteristics of AC/DC hybrid microgrid composed of power router,the power router is divided into three working states,and its switching conditions are analyzed.This paper adopts hierarchical coordinated control for the ports of the electric energy router.The dispatching layer makes judgment according to the state of each port and bus fed back by the microgrid control layer,sends working condition instructions to the microgrid control layer,drives the action of the bottom control layer,and maintains the stability of the electric energy router.Finally,part of the measurement and control circuits are designed,and the single router simulation and multi router simulation models are built by using Matlab/Simulink.The simulation analysis shows that the control strategy adopted in this paper can ensure the power quality of the user side under the condition of realizing the power balance between AC and DC hybrid microgrid and grid connection.