Research On Voltage Coordination Control Strategy Of Multi-Converter For DC Distribution Network

Distribution system based on DC could be superior to an AC system in terms of efficiency,reliability and distribution capacity,and better absorb the distributed energy.Therefore,the flexible DC distribution system,has a huge market potential and economic value.Therefore,it is paid close attention and its engineering practice and research are in full swing within the whole world.Control is the key of DC distribution system.Effective and reliable DC voltage controllers need to be designed and the coordination control between converter stations should be researched,for ensuring dc voltage stability and power balance under all operation conditions.In the paper,a three-layer hierarchical coordinated control system of DC distribution network is proposed.First,the paper introduces converter control layer and finishes accurate modeling and analysis of related characteristics of each unit of DC distribution grid,including mathematical modeling and control of PV,energy storage,DC-DC converter,voltage source converter and load converter.Based on DC voltage margin control and droop control,hybrid control method is proposed,which is validated by simulation.Then,simulation and data analysis for several basic control methods and hybrid control method are made in the multi-terminal flexible DC distribution system,and related conclusion is get.On this basis,the paper proposed multi-Converter voltage coordination control strategy for DC Distribution network.Each power electronic converter coordinates its control method by instruction value to keep the power balance of the DC grid under different operating conditions.Each unit is controlled independently without communicating with each other,which is decentralized and autonomous.The concept of secondary voltage regulation is put forward in the upper layer control,and analysis of operation optimization is made.One of the concerns is the operation requirement of the system,which will solve the problem of power fluctuation in the condition of fault and load variation.Accordingly,the related control strategy of DC distribution network are studied and designed,which leads to a better control effect and can ensure DC voltage stability.