| With the scale of power transmission from the west to east increasing continuously and the construction of Shandong electric power grid accelerating, the reliability of power grid is becoming increasingly important.Composite generation and transmission system is the main part of the power system, and it is constituted by many kinds of electric equipments. Its structure and operating mode are very complicated because the fault modes are often overlapped and correlated. So it plays an important role in the reliability evaluation of power system reliability assessment.The reliability assessment of composite generation and transmission is studied in this thesis and the reliability of the 500kv main grid is assessed and analyzed. The main topics of this thesis are as follows:(1) The basic concept of power system reliability including composite generation and transmission system is summarized. The development and application of Monte-Carlo method in the reliability evaluation of power system compared with analytic method is introduced.(2) The basic principle of Monte-Carlo method and its characteristics are introduced, combining scattered sampling technique with importance sampling method, an improved importance sampling method for power system reliability evaluation is proposed. The method can reduce the variance dramatically. The calculation results of IEEE-RTS show the efficiency and validity of this method.(3) The reliability evaluation mathematical model and algorithms are established. The corresponding calculation programs are developed. Based on the proposed method, the contribution of generation system and transmission system to the reliability are calculated separately, the DC flow and a minimum load cutting model are used to evaluate the sample state.(4) The 500kv grid of Shandong is computed and analyzed. The weak parts of the system are found and the improving schemes are suggested. |
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