Research On Coordinated Source-load Optimal Dispatching Method For Flexible Dc Distribution Network

The traditional urban AC distribution network has the problems of insufficient power supply capacity and poor power quality.With the development of distributed power and DC loads,the DC distribution network can accommodate various distributed power sources and DC loads flexibly and efficiently,besides having larger power supply capacity and better power quality than the AC distribution network.Applying flexible DC technology,DC distribution network can achieve reliable voltage and power control to meet the needs of the flexible operation of DC distribution network.In view of the lack of a reliable control and dispatching method for the existing DC distribution network research,this thesis studies from three aspects: steady-state operation analysis,safe operation margin and optimal dispatching method.This thesis discusses the operating mechanism of the droop characteristics of the converter in a flexible DC distribution network,analyzes the requirements of the droop characteristics for different types of buses,and presents the secondary regulation and third regulation of the converter droop characteristics,which can be used as the basic dispatching control method.Considering the effect of the DC power flow controller,a power flow algorithm of flexible DC distribution network with droop characteristics is established.By analyzing the safe operation margins of the bus voltage and transmission power,a safe operation index suitable for flexible DC distribution network is established.A new responding index is proposed considering both the voltage error and power error.On the one hand,a PI control process is applied to determine the amount of power adjustment to restrict the responding index in a reasonable range.On the other hand,the application of a genetic algorithm process aims to optimize the power distribution coefficient for minimum network loss,to meet the economic operation requirements.The proposed power flow calculation method,safety operation index and optimal dispatching method are validated through a typical eight-terminal flexible DC distribution network.The results show that the proposed optimal dispatching method can improve the safe operation level and economic operation ability of the DC distribution network.