Research On Power Supply Fast Switching Technology Based On Three-Port Flexible Multi-State Switch

The increasingly "multi-source" characteristics of distribution network make the development mode of traditional distribution network no longer meet the needs of distribution network development in the new era,but also put forward higher requirements for the security and reliability of distribution network power supply.As a new type of device adopting new power electronics technology,the flexible multi-state switch,compared with conventional tie-in communication switch,can realize continuous and flexible regulation of power flow,flexible switching of operation modes,promote the balance of feeder load distribution and improve power quality.In this paper,three-port flexible multi-state switch with back-to-back structure is taken as the research object.Firstly,the stable working principle between three-port flexible multi-state switch and the three AC systems is analyzed.Proposing and analyzing the dynamic mathematical model of three-port flexible multi-state switch in the synchronous rotating dq coordinate system under the two operating states such as normal grid-connected and fault-off network,and the principle of inter-power exchange between ports is obtained.On this basis,three-port flexible multi-state switch coordinated control strategy is selected for different operating states to achieve different control objectives.Then,a load transfer optimization model and a power flow reciprocity optimization model considering power loss,feeder load balancing factor and network loss are designed.The GAMS software is used to solve these models to obtain the optimal power replenishment value of normal grid-connected sides in the three ports and the optimal power allocation value of three ports.These value are used as the active power reference values of power control to achieve the optimization of fault recovery control and threeport optimal power flow control respectively.The effectiveness of the optimization is verified by the results of numerical examples and simulation experiments.Finally,the comparison between the hard-switching mode and the controller state tracking control mode is adopted to realize the fast and smooth switching between the normal grid-connected operation state and the fault off-grid operation state of the threeport flexible multi-state switch.The simulation of the three-port flexible multi-state switch switching from normal grid-connected to fault off-grid and from fault off-grid to normal grid-connected is built in the environment of Matlab/Simulink.The platform validates the effectiveness and superiority of the controller state tracking control strategy.