Research On Virtual Inertial Control Strategy Of DC Distribution Network

With the increase of the penetration of distributed power in the power grid and the high-density access of DC loads,the development of DC power distribution networks has been promoted.Compared with AC power grids,DC power distribution grids do not have problems such as frequency and power angle stability,reactive power circulation,and three-phase imbalance.The overall control and scheduling are relatively simple,and the power supply reliability of the system is relatively high.However,due to the isolation of the converter in the DC distribution network,its own inertial support capacity is small,and the voltage fluctuates significantly with power.In order to improve the problem of low inertia of the DC power grid,this paper studies the virtual inertia control strategy of the DC power distribution network,improves the system's ability to suppress the sudden change of DC voltage under disturbance conditions,and improves the quality of the voltage.The specific work of this article is as follows:This paper first analyzes the topology structure and control method of the DC distribution network,and introduces the specific components.Establish mathematical models of wind power generation,photovoltaic units,energy storage units,grid-connected converters and load units,and analyze their working principles and control strategies.Based on this,a DC power distribution system is established for subsequent virtual inertia control.Technology lays the foundation.Secondly,on the basis of the concept of AC grid inertia,the inertia of the DC grid is defined,so that the DC side virtual capacitor inertia is derived,and combined with the DC grid voltage droop control,the relationship between the converter droop coefficient and the virtual capacitor inertia is obtained.Research on inertial control strategy based on variable sagging coefficient of battery-side converter to improve the inertia of the system and suppress the sudden change of DC voltage.At the same time,it is compared with fixed inertia control.Compared with the droop coefficient of droop coefficient,DC voltage can be stabilized better.Mutation.Finally,based on the layered control voltage,adaptive capacitive inertia control is used to increase the system inertia.By analyzing the curve of the power fluctuation to the system voltage and voltage change rate,the capacitance inertia with the degree and trend of the voltage is improved accordingly.When the voltage fluctuates,the appropriate capacitance value will be virtualized on the respective DC sides according to the inertia coordinated control to the system provides inertial support.Comparing this adaptive control strategy with traditional virtual control,it can effectively improve the response speed of the system while ensuring that the system voltage is stable.