Study On Three-phase Unbalanced Control Of Low-voltage Distribution Network Based On Electric Spring

Low-voltage distribution network is in direct contact with users,and its power quality will directly affect the quality and satisfaction of users.And three-phase imbalance problem is one of common power quality problem in low voltage distribution network,relatively at present rely mainly on electric power sector through the way of operation adjustment is roughly balanced three phase four wire system low voltage distribution network in each phase of power load,needs to be more dynamic governance technology more reliable and efficient real-time control three phase unbalanced problem in low voltage distribution network.Therefore,this paper proposes to apply the emerging power spring technology to the three-phase unbalanced treatment of low-voltage distribution network,mainly doing the following work:Firstly,the basic situation and research status of three-phase unbalance in lowvoltage distribution network are introduced,and the treatment methods of traditional three-phase unbalance are briefly introduced.Then introduces the main technical points and development of the electric spring,mainly introduces the concept of the electric spring,the main topological structure and control mode of the electric spring.Then the single-phase power spring is applied to the three-phase unbalance control of the low-voltage distribution network,the mathematical model of the fully compensated type power spring is established,and the single-phase power spring controller based on PI controller and phase control strategy is designed.The effectiveness of single-phase power spring in the treatment of three-phase unbalance in low-voltage distribution network is simulated and verified by SimPowerSystems power system toolbox in Matlab 2012/Simulink.The results show that single-phase power spring can effectively suppress three-phase voltage unbalance in low-voltage distribution network.Finally,the three-phase power spring is applied to the three-phase unbalanced management of low-voltage distribution network.According to the characteristics of three-phase unbalanced management,the three-phase power spring topology with double isolating transformer is selected.Then,the three-phase power spring controller is designed based on the quasi-proportional resonance controller and the delta Angle control strategy.In addition,the effectiveness of three-phase power spring in the case of load asymmetry,power supply asymmetry and load and power supply asymmetry is also verified in Matlab.The results show that three-phase power spring can effectively solve the three-phase imbalance problem in low-voltage distribution network under more complex conditions.