Research On Electromechanical Oscillation Analysis And Control For Situational Awareness Of Interconnected Power Grids

Having reviewed the emerging phenomena of synchronous or even asynchronous interconnection among regional power systems and large-scale distributed energy being integrated into power grids emloying power electronics technology,it is apparent that their operation efficiency are improved and their energy structures are optimized,nevertheless,the dynamic characteristics of these large-scale interconnected power systems also become more complicated.As for WAMS?Wide Area Measurement System?and the developing SA?situational awareness?technology,one of its important functions is to provide the key information involving with these complex dynamic behaviors in the interconnected power systems,which include modal information,interactive paths of electromechanical oscillations,responses to corrective or preventive control measures,etc.However,to this end,it is very necessary to research the issues concerning the relative local quantization index,modal evolution,generator coherency identification,dynamic reduction,prevention control,correction control,emergency control,PSS?Power System Stablizer?placement and WADC?Wide Area Damping Control?configuration.Therefore,this thesis focuses on the theory and methodolgy about situational awareness for large-scale interconnected power system based on power electronics technology,especially on the quantitative analysis and control of electromechanical oscillation.the detailed works invloving theoretical research and simulation experiment may be described as follows.At first,the developments of WAMS and SA technology for PEEPS?Power Electronics Enabled Power Systems?are investigated.The mechanism of electromechanical oscillation?EMO?is summarized and discussed.Then the idea about evolution of EMO mode is proposed.From the perspectives of model-driven and data-driven,or offline and online,the offline model-based EMO analysis method and the online measurement based method are reviewed and discussed.Meanwhile,the main control measures of EMO are expounded.In addition,the basic theories and methods related to EMO,such as eigenvalue analysis method as well as power system stabilizer design are reviewed for providing necessary background knowledge and support for the subsequent chapters and consequently improving the readability of this paper.Secondly,in order to develop the SA technology for large scale PEEPS,this paper proposes an improved quantitative indicator for the relative localness of EMO mode,from the point view of flexibly adjusting the parameter according to the system size.The eigenvalue analysis may be implemented based on small-signal model,then the exponent parameter could be optimized in the closed interval of participation factors using the dichotomy.Consequently the index can be obtained from those normalization factors for an EMO mode.It has the advantages of computational efficiency and practicality compared to the traditional indicator.The case studies have been carried out on a Kundur 4-machine and 11-bus system and an IEEE 50-machine and 145-bus system,utilized by the PST simulation tool package inMATLAB environment,and the results show the effectiveness and adaptability of the proposed index.Thirdly,the impacts of different boundary conditions such as generator type,power flow of tie line,and spinning reserve capacity on the modal localness of and the participation feature of generator for EMO mode have been studied.The case studies have been carried out on a Kundur 4-machine and 2-area system and its variants,utilized by PSS/E V33,and the results verify the effectiveness of L_idx which could be helpful to track the evolution of inter-area mode or local mode.Moreover,it indicates that the participation feature of generator would be changed and consequently modal property would be transformed from local mode to inter-area mode or vice versa if the boundary condition is significantly varied for instance the fluctuations from load consuming or power generating and the integration of doubly-fed induction generator?DFIG?.Furthermore,it is possible to predict the generator with maximum participation for inter-area mode when the DFIG is integrated into a regional power grid.Fourthly,the significance and potential application value of generator coherence identification in online dynamic safety analysis,preventive control,correction control and emergency control and dynamic reduction are discussed.Then the coherent generator identification is described from the aspects of the model-based method and the measurement-based one.The coherent group identification method based on relative localness index is presented.Using an IEEE 10 machine 39 bus system,it is verified that the coherency of generator identification method based on the relative localness index has better performance compared with the traditional slow mode based method.It may provide a new way for coherent group identification,dynamic reduction,and preventive control.In addition,the preventive control measures such as generator rescheduling employing the measurement based generator coherence identification are studied.Its feasibility is verified by an IEEE 50 machine 145 bus system.At the end,PSS is an additional control for the power electronics converter based exciter,which is very useful for damping control of power system.The studies on the PSS design and WADC configuration with the help of the dominant interarea oscillation?IAO?path identification are carried out,especially from the perspective of the interaction path of EMO mode.Taking a 10-machine 39 bus system as an example,the damping effect of the PSS on the generators strategically situated at the either ends of the dominant interarea oscillation paths and outside these paths have been compared.Meanwhile,it may be analyzed how the PSS configuration using local signals affects different IAO modes in an interconnected system.Furthermore,it is found that placing of WADC gives additional damping effect to the system with the placement of local PSS.