Research On Vlotage Stability Of Power System With The Wind Farm

In recent years, with the gradual depletion of traditional energy and the increasing seriousness of environmental pollution, the new energy power generation technology represented by the wind power is developing rapidly. However, because of the randomness and fluctuation of wind power, the high wind power penetration result in huge impacts to grid, and the voltage stabilit y is particularly prominent among them, which has become the bottleneck of wind power integration. Until now, research on the voltage stability caused by the wind power is mostly using static method, lacking dynamic analysis. In this paper, the impacts cau sed by the intergration of wind power on voltage stability is presented.First, this paper analysis the impacts of voltage stability caused by on-load tap changer(OLTC), generator over excitation limiter(OXL) and the dynamic characteristics of load, verified the nature of voltage instability is dynamic, and closely related to the dynamic element in power system. These researchs lay the foundation for analysing the dynamic voltage stability in wind power system.Next, the dynamic reactive limit of DFIG is derived, and time domain simulation is used to analyze the influence of the dynamic reactive limit and the different operation modes of DFIG on the dynamic voltage stability of power system. Simulation results show that the dynamic reactive limit play an imp ortant role in voltage stability, not simply as a fixed value; in addition, when DFIG grid side converter at voltage control mode, the reactive power generated by DFIG can reach maximum, which can improve voltage stability of power system.Then, this paper deduces a linear DFIG model for small signal voltage stability analysis, and the relationship between DFIG and dynamic voltage stability is dicussed by small signal stability analysis. Although the dynamic characteristics of the system can be directly observed though the simulation, it is difficult to find the essential reason of voltage instability. So, in order to reveal the relationship between DFIG and dynamic voltage instability, the trace of system eigenvalue and the participative factor in voltage instability is observed.At last, to obtain new voltage stability index, which can be accurately considered DFIG dynamic characteristics, the conventional multi-port equivalent network has been modified, and the new index can be applied to the voltage stability monitoring. Simulation results show that improved index has the advantages of high sensitivity and good precision, which can accurately reflect the current voltage stability of the power system.