DC Distribution System Configuration And Steady State Voltage Control

Power distribution system is showing an unprecedented diversified development trend with the social progress and economic development.AC distribution network shows a series of drawbacks.DC power distribution technology can effectively solve the challenges of power distribution system.It is of great significance to study the construction,steady-state voltage control of DC power distribution system.At present,the research of DC power distribution system mainly focuses on low voltage power supply system.In this paper,the steady-state modeling and voltage control of DC power distribution system are studied based on multi-stage DC power distribution system construction.First of all,this paper analyzes the constraints that affect the construction and the basic structure of DC power distribution system.A hierarchical partition DC distribution system is presented who contains multiple voltage level.It can be used as a possible form of the future distribution network and can effectively solve the challenges faced by the future distribution system.The data center is selected as a case of low voltage DC distribution system.This paper simulates the DC power supply scheme for the data center in the normal operation,the main power source out and short circuit failure.The results show that the proposed data center DC power supply scheme can always ensure the stability of the DC bus voltage and can be coordinated with the existing AC system.Secondly,a flexible steady state mathematical model of DC distribution system is established combining the existing mathematical models of the main components of DC power distribution system.The model includes VSC master-slave control and droop control as well as DC transformer control which make it more applicable.The power flow of DC distribution system is calculated by using the unified iteration method,the results show that the voltage in the DC distribution system is within the reasonable range and prove the validity and reliability of the established mathematical model.The steady state mathematical model lays a good foundation for the steady voltage control of DC distribution system.At last,two kinds of voltage fluctuation of DC distribution system are analyzed.The DC voltage disturbance under the master-slave control of DC distribution system is studied.This paper simulate the influences on DC voltage fluctuation of AC/DC power fluctuation,distributed power supply output fluctuation and load switching by PSCAD.Finally,methods to suppress the DC bus voltage fluctuation are proposed from improved AC/DC converter control method,improved cooperative control method,coordination of distributed power output or adjusting the controllable load.