Research On The Integrated Voltage Regulation Control Strategy Of DC Distribution Network

With the continuous development of distributed generation technology,MTDC technology and new type DC equipment,DC distribution network has been paid more and more attention and research.Compared with the traditional AC distribution network,the DC distribution network can reduce the amount of DC/AC converter link and the cost of construction and operation of the converter station.DC distribution network does not exist the problem of reactive power circulating current,frequency stability and power angle stability,can effectively solve the problems of power quality,such as three-phase imbalance,power network harmonics in AC distribution network.In this paper,the control strategy of voltage regulation and control of DC distribution network is studied,and the main research contents are as follows:(1)The typical topology of DC distribution network and the basic principle of voltage source converter(VSC)are analyzed,and the steady state mathematical model of VSC is established.Then the hierarchical control system of DC distribution network is analyzed,and the converter station controller which includes outer loop controller and inner loop controller,which are used to provide the basis for designing the DC voltage control strategy of DC distribution network.(2)The principle,advantages and disadvantages of the DC voltage droop control strategy used in the DC distribution network are analyzed.Based on the voltage deviation problem existing in the DC voltage droop control strategy,an improved DC voltage droop control strategy which uses additional DC voltage deviation compensation control is proposed,which can reduce the DC voltage error and improve the reliability of power supply in the DC distribution network.The simulation model of two-terminal and three-terminal structure of DC distribution network is built,and the simulation results validate the effectiveness of the proposed control strategy.(3)The integrated voltage regulation control strategy of DC distribution network is studied,the voltage control system of DC distribution network is designed,and the primary voltage regulation and secondary voltage regulation of DC distribution network are analyzed and studied in detail.The multi terminal DC voltage droop control based on the characteristics of U-P is used in the primary voltage regulation.According to different optimization objectives: voltage optimization,network loss optimization,network loss and voltage optimization,integrated voltage regulation control strategy based on voltage optimization algorithm,integrated voltage regulation control strategy based on network lossoptimization algorithm,and integrated optimal control strategy of voltage and network loss in DC distribution network are respectively put forward in the secondary voltage regulation,which provides reference for the voltage control and optimal operation of large scale DC distribution network in the future.(4)The simulation model of integrated voltage regulation of the DC distribution network is built,and the integrated voltage regulation control strategy based on voltage optimization algorithm,integrated voltage regulation control strategy based on network loss optimization algorithm,and integrated optimal control strategy of voltage and network loss in DC distribution network are respectively simulated.The simulation results validate the effectiveness of the proposed control strategy.