Power system analysis criteria-based computational efficiency enhancement for power flow and transient stability
As modern power systems have been operated closer to their security limits, the importance of their static and dynamic security assessments is increasing. However, due to the large-scale nature of an interconnected power system and the nonlinear characteristics of power system equations, computational limits impose severe constraints for such security assessments. It is thus critically important to develop rapid and precise power system analysis tools, which are fundamental for the security evaluations. In this dissertation, comprehensive approaches to both reduce the computational requirements and to achieve a high level of simulation accuracy are examined for application to power system steady-state solutions and transient stability analyses. Three approaches are proposed and validated, which are a mixed power-flow analysis, a mixed transient stability analysis, and an exciter model complexity reduction. The first approach, a mixed power-flow analysis, focuses on reducing the computational complexity of the steady-state solution. The approach combines ac and dc power flow models to decrease the number of required computations while still capturing variations in the external system. A high level of accuracy in the targeted central part of the system is achieved using the detailed ac model. The less detailed dc model is used for the external system to reduce computational requirements without neglecting it altogether. In the second approach, the mixed power-flow analysis is extended to transient stability analysis. This method reduces computational requirements for power system transient stability simulation while retaining important dynamic information. In order to prevent the loss of simulation accuracy, the real power losses ignored by the standard dc model are compensated for in the external system. Finally, the exciter model complexity reduction approach is presented for further improved transient stability analysis. This topic investigates conditions in which fast modes of the exciter model can be neglected or must be preserved. When the fast modes can be ignored, a simpler model with those modes removed replaces an original model and simulation steps can be increased without numerical stability issues. During a transient simulation, the proposed method switches dynamically between the original model and the reduced model, depending on the switching criterion presented.
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