Voltage Control Strategy When The Flexible Multi-state Switch Port Is Unbalanced

With the new round of energy revolution sweeping the world,a lot of distributed power sources are connected to the power grid,and the current flow in the distribution network has become increasingly complex,which has seriously affected the power supply reliability of the distribution network and greatly reduced the quality of the system power supply.As a new type of power electronic equipment,flexible multi-state switches are increasingly replacing traditional contact switches with their ability to flexibly adjust the flow direction of the connected feeders and flexible control methods,and play an irreplaceable role in increasing the power supply capacity of distribution network.This paper takes the three-port flexible multi-state switch with B2B voltage source structure as the research object.First,it makes a simple analysis of its working principle,introduces several commonly used topologies,and establishes a three-port flexible multi-state switch inThree-phase static abc coordinate system,two-phase static coordinate,and three mathematical models in dq rotating coordinate system are analyzed based on the DC voltage stabilized U_dcQ control,constant active and reactive power PQ control,and constant voltage and Frequency VF control strategy.Then,the three-port flexible multi-state switch has a detailed analysis and derivation of the DC side voltage pulsation in the case of single port and multi-port unbalance,and it is obtained that both single-port and multi-port unbalance will occur on the DC side.Conclusion of voltage pulsation at 2 times the frequency.And on this basis,according to the principle of the capacitance compensator,a control strategy based on sliding mode control is designed.By compensating the pulsating power to suppress the DC side voltage pulsation,the parameters of the controller are designed.MATLAB/Simulink built a three-port flexible multi-state switch simulation model,and analyzed and verified the effectiveness of the proposed strategy.Finally,in order to obtain a more excellent DC side voltage suppression effect,a nonlinear interference observer is added to the controller,and the required pulsating voltage and power information are collected through the nonlinear interference observer,and then the compensator needs The compensated pulsating power information can better compensate the pulsation of the DC side voltage.The parameters of the controller are also designed.Similarly,a simulation model of a three-port flexible multi-state switch is built in MATLAB/Simulink to verify the effectiveness and superiority of the proposed method under a variety of different working conditions.