Analysis And Research Of DC Distribution System Compatible With Distributed Generation

Due to unavoidable three-phase unbalance, voltage fluctuations, voltage flicker, frequency fluctuations, harmonic pollution and other power quality problems and the fact that the transmission capacity constraints caused by the presence of reactive power, traditional AC distribution network has been unable to meet the requirements of electrical equipment. The DC distribution network has significant advantage on improving operational efficiency, reliability and power quality, and secure access of new energy and other critical issues.The research of DC distribution network of the countries are still in the experimental stage of exploration, The research is still less for its in-depth study, but it can be expected that the DC distribution network with a strong technical and economic advantages will have broad prospects for development.Firstly, this paper introduces the development status of dc power distribution network at home and abroad, and gives a detailed discussion of its technical features and advantages with distributed generation. Secondly, the paper gives comprehensive exposition of dc power distribution system architecture, including the medium and low-pressure system topology, the standard voltage and bus structures and so on. Finally, through the study of its control mode and unit module proposing a bi-directional DC/AC and DC/DC two-stage network interface, and adopts relatively independent double-loop control strategy and single-loop DC/DC control of DC load and double-loop DC/AC control of AC load.Combined with the smart grid research institute and the Inner Mongolia company’s cooperation project, providing a DC power distribution network solution for a certain experimental zone users. Selecting AC/DC capacity of300kW, PV capacity is50kW,66kW AC load and DC load of94kW. In order to improve the reliability of DC power distribution network, this paper chooses four normal operation the rest one used as backup inverter. In view of low-voltage DC power distribution system, this paper simulates three different patterns of AC main three-phase imbalance, dc load suddenly increases, and sudden decrease of PV outputs. The simulation study results show that the two-stage network interface can stabilize DC bus voltage well and load-side voltage can be maintained near its rated value, the system can also maintain the power balance, all of these verify the effectiveness of the proposed control strategy and the feasibility of DC distribution system.