Application Research Of VSC DC In Urban Power Grid

Due to the sustained rapid growth of city load and the continuous increasing demand for safe and reliable power supply,urban power supply with high quality and reliability is facing more and more difficulties and challenges.For the catastrophic blackouts,the newly emerging microgrid technology is a beneficial complement for urban power network and has become an effective means for improving power supply reliability. VSC DC provides a new technical method for the construction of urban high voltage power network,and also provides a solution for the access of micro grid to large power grid.So,it is of great significance to study on the application of VSC-HVDC on urban power network.In this paper,the characteristic of city load center is analyzed and the application of VSC-HVDC on urban power network is studied from high voltage level and middle voltage level:two level model and a mathematical model for three-phase voltage source inverter based on switching function are built,and a multi-objective decoupling controller for voltage source inverter is designed:three level VSC DC simulation system with good controllability of power flow and power reverse is built based on RTDS;the example of test system and the real typical simulation system of urban power network are built using PSS/E software,based on which the ability of VSC DC to improve transient stability,the ability to reinforce damping and suppress low-frequency oscillation,and the ability to provide reactive power support so as to improve system voltage stability are all verified;fuzzy control technology is adopted in the control of damping low-frequency oscillation,its effectively and adaptability of damping are proved through PSCAD software;for the power network with VSC-HVDC as tie line, the VSC DC and soft start control based black start and restoration scheme after black out is studied and compared with traditional black start, and the VSC DC based soft start control has great superiority;the idea of whole process control for urban power network is put forward;the access mode of micro grid to large power grid based on VSC DC is proposed, and its advantages over alternating current access and access through CSC are illustrated.The excellent qualities of VSC DC's application on urban power network are demonstrated from various aspects in this paper,thus provides important reference value for future practical application of VSC DC in urban high voltage and middle voltage power network.