Research On Dynamic Models And Wide-Area Damping Control Strategy In Hybid AD-DC Power System

With the development of large-scale AC/DC interconnected power system in our country,the network structure has deeply changed and the whole system operation condition shows new characteristics.Long transmission distance from the energy center to the load center and heavy loading lead to inter-area low frequency oscillation,which constraints transmission capacity seriously and threatens the safe and stable operation of the whole power system.Eigen-value analysis method of Low frequency oscillation depends on the detailed system modeling which is based on component physical mechanism,and system linearization at operation point,and its eigenvalue and eigenvector analysis.At present,most of the commercial power system analysis software adopts this method.However,due to the regional differences of the system components and the new components are putting into use in series,the dynamic component model library provided by the commercial analysis software can’t meet the practical demand in engineering.Therefore,it is the basic of analysis of low frequency oscillation and of great practical value to improve the dynamic model library of the commercial software.With the development of wide area measurement technology,the technology of monitoring,analysis and control of low frequency oscillation based on measurement information is developing rapidly.The measurement information reflects the actual system operation condition,and the system model established by using identification technology according to the measurement information reflects the actual characteristics more directly.Therefore,analysis and controller design method based on the identified model have great significance.However,the traditional identification methods need to be further improved in accuracy and how to select the maximum damping of the system during a large number of controllable components need to be studied.To solve the problem that the dynamic model library cannot meet the needs of practical engineer,the thesis compares the dynamic model library between BPA and PSS/E.The exciter,turbine&governor and power system stabilizer model those cannot correspond to BPA are established in PSS/E,and the correctness of the model is verified by simulation in single machine system.To solve the inter-area low frequency oscillation problem,a power system state space model identification method based on multiple linear regression is proposed,the result of the identification of a mathematical model and power system proves that the proposed method has higher accuracy than the subspace method;the reduced order state space model of a test system and a practical power grid is established by using the proposed identification method,the best controller installation position is selected by using the geometric index on the identified model,and HVDC damping controller is designed by phase compensation method,test system and practical system simulation show that the proposed HVDC damping controller designed method can select the best installation location and apparently improve the system damping.