| Power systems are more and more complex due to the interconnection of regionalpower grids and the integration of large-scale renewable energy, such as wind power.Thus the security and stability issues of power systems are becoming increasinglysignificant. The power dispatching is in the front line of assuring the security andstability of power systems, therefore it is urgent to develop new methods and toolswhich can effectively deal with the security and stability constraints in powerdispatching. Besides, with the increasing of wind power penetration, the double fedinduction generator (DFIG) has brought great challenges to the security and stabilityof power systems. In view of the above issues, based on the Security Region (SR)approach, this dissertation has conducted the following studies.Firstly, based on the fact of―within the acceptable range of engineeringapplication, the boundary of Security Region can be approximately represented byone or few hyper-planes‖, a novel security-constrained unit commitment model withfive sub-objectives is presented, which considers the operating constraints of units,system constraints and network security constraints. Compared with the traditionalUC model, it has the following features: a. for the first time, the power flow constraint,the static voltage stability constraint and the transient stability constraint are takeninto account in UC at the same time, therefore it serves as a useful tool for powerdispatchers to deal with the network security constraints; b. the model evaluates thesecurity margin of dispatching schemes by the distance from the current operatingpoint to the boundary of SR and takes the operating cost and the security margin asoptimization objectives, therefore, it provides a novel method for power dispatchers tobalance both of the security and economy of power system operation in UC.Secondly, the small signal stability region (SSSR) for power systems with DFIGis evaluated and the corresponding relationship between the SSSR boundary andelectromechanical oscillations is analyzed. The impact of DFIG as well as its locationon the small signal stability of power systems is studied through SSSR. Through lotsof simluation, it is found that within the acceptable range of engineering application,the boundary of SSSR for power systems with DFIG in power injection space can stillbe approximated by one or a few hyper-planes, which laies the foundation for theapplication of SR approach to the small signal stability ananlysis and control of powersystems with DFIG.Thirdly, a new security region-based probabilistic small signal stability analysis (PSSSA) method for power systems with DFIG is proposed. Compared with thetraditional PSSSA method based on eigenvalue analysis, the method proposed in thedissertation is of great computational advantages and can effectively reduce thecomputation burden of considering the uncertainties of wind power and load in thesmall signal stability analysis of power systems. And a model of small signal stabilityconstrained optimal power flow based on SSSR is also proposed, which improves thesmall signal stability of power systems with DFIG through power redispatching andwind curtailment. It can overcome the difficulty of the explicit description of smallsignal stability constratints in traditional methods.Lastly, the dynamic security region (DSR) in the injection space assuring thetransient stability of power systems with DFIG is studied and the impact of DFIG onDSR is analyzed. Furthermore, the mechanism of the change of DSR is studied.Extensive simulation results show that, within the acceptable range of engineeringapplication, the boundary of DSR for power systems with DFIG in power injectionspace can still be approximated by one or few hyper-planes, which provides aneffective tool for the security monitoring, assessment and control of power systemswith DFIG. |
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