Research On Key Fundamental Techniques For Fast Stability Analysis On Large-scale Power Systems

With the gradual interconnection of large-scale regional power networks in China, there is an urgent need for developing new fast simulation techniques for power system on-line dynamic stability assessment (DSA). This thesis proposes a novel method for power system transient stability simulation based on the techniques of hierarchical tree model, which deal with contents of partitions among the electric power networks and describe the structure mathematical model in the simulation, bi-directional iteration, the key formulations for updating variable corrections, the algorithm schematic flow and the method for overcome oscillation phenomena in the system simulation, etc. The main results of the thesis are summarized as follows.A partition method for a large-scale power network is proposed. The partition reflects the geographical features of a large-scale power grid by incorporating the aggregation of the pivot nodes and weighted leaf nodes in a leveled-tree model. The model is thus derived in a structural construction which is well embodied in the hierarchical organization of system components and properly highlights the impact of dynamic elements on the system simulation. A standardized procedure for constructing the structural model is developed to describe the system model.To calculate the variable corrections in the iteration process using implicit trapezoidal integration method for the system simulation, a bi-directional iteration technique is proposed on the basis of the hierarchical tree model. The variable corrections of system components are computed by an approach of forward simplification and backward substitution. An algorithm is provided for complete implementation of this leveled-tree based bi-directional iteration-based the system simulation. The accuracy of the new technique of system simulation is validated by comparing the results with the well-accepted commercial software BPA.Unlike the traditionally popular partitioned solution with either explicit integration or implicit integration methods, the new simulation method is highly efficient with less iteration without interface errors. It is also suitable for adding new components for increasing new functions of simulation software and implementing in a distributed or parallel computation environment. It offers great potential for development of an on-line dynamic security analysis tool.Besides, the thesis proposes a new sensitivity approach for fast stability limit assessment. Based on the improved TEF and optimal control principle, the approach can calculate the stability margin and its sensitivity for transient stability limit analysis quickly.Finally, the thesis reports the works on robust controller design in power systems. A robust decentralized guaranteed cost excitation controller is proposed using a linear inequality technique and genetic algorithm together to tune the parameters of the controller in an optimal way. The effectiveness of the controller is demonstrated on a small-scale test power system.