An In-Depth Study of Complex Power System Dynamic Behavior Characteristics for Chinese UHV Power Grid Security

In this paper,a series of major policy decisions used to improve the power grid reliability,reduce the risk and losses of major power outages,and realize the modernization of 21st century power grid are discussed. These decisions were adopted by American government and would also be helpful for the strategic development of Chinese power grid. It is proposed that China should take precaution,carry out security research on the overall dynamic behaviour characteristics of the UHV grid using the complexity theory,and finally provide safeguard for the Chinese UHV grid. It is also pointed out that,due to the lack of matured approaches to controll a cascading failure,the primary duty of a system operator is to work as a "watchdog" for the grid operation security,eliminate the cumulative effect and reduce the risk and losses of major cascading outages with the help of EMS and WAMS.

Contribution of UHV Grid to United National Power Market

Power market construction is an important part of the marketization reform in China's electric power industry and an essential part of the economic system reform in China. With the social and economic development, the contradiction between distribution of energy resources and development of regional economies gets increasingly noticeable, and a united national power market is consequentially required to optimize the allocation of energy resources over the whole country. Analyses indicate that the development of UHV grid will provide a strong material support for the united national power market by expanding market coverage, lowering load fluctuation and promoting diversif ication of power resources.

Component Analysis and Calculation for Social Benefits of UHV Assessment

With the rapid development of the UHV power grid, evaluation of the economic and social benefits of the UHV power grid is conducive to guiding the planning and construction of UHV power grid. At present economic benefit evaluation system of the UHV power grid is driving to maturity stage on the whole at home and abroad, but it invariably tends to regard social benefits as part of economic benefits, without evaluating social benefit separately. The social benefit evaluation model of UHV power grid is built in case of sufficient investigation. The differentials between social benefit and social cost are calculated respectively by three kinds of solutions according to the constructed social cost evaluation index system and social benefits evaluation index system, conclusion that UHV power grid transmission has better social benefits can be reached by contrastively analyzing the social three kinds of solutions corresponding to benefits. At last, the evaluation model and method are verified and analyzed through the analysis of engineering projects.

Evaluation of optimal UPFC allocation for improving transmission capacity

A unified power flow controller(UPFC)combines the advantages of various flexible alternating current transmission system(FACTS)devices into a powerful format.Using a 500 kV power grid,this study evaluates the selection and use of a UPFC to improve transmission capacity.The"UPFC unit capacity control proportionality coefficient"is introduced to quantify the control effect of the UPFC,and an optimal calculation method for the UPFC capacity is presented.Following the proposal of a UPFC site selection process,the data of an existing power grid is used to conduct simulations.The simulation results show that the UPFC has a strong ability to improve transmission capacity,and its use is greatly advantageous.Additionally,by applying the proposed selection method,the control effect and economic benefits of the UPFC can be comprehensively considered during project site selection.These findings have a guiding significance for UPFC site selection in ultra-high voltage power grids.