| Accurate assessment of future transmissio n network utilization is important for transmission planning.According to the 9th power industry reform document,revenue of electric power companies will come from transmission and distribution tariff approved by government in future.Utilization of powe r grid equipment will determine income of electric power companies to some extent,and will be a major factor in economic evaluation of transmission planning.This paper mainly focuses on the evaluation of future transmission network utilization on account of the deficiency of current studies.Overview on present research situation,a relatively complete index system of transmission network utilization is built considering the main influencing factors.A practical calculation method of utilization indices is introduced,and a quantitative evaluation method of future transmission network utilization is proposed for actual transmission planning.The transmission network utilization indices are calculated by an improved probabilistic load flow algorithm based on Monte Carlo simulation.On the basis of conventional probabilistic load flow model,a new generation dispatch method considering security constraint is first introduced.The security constraint model is built by DC sensitivity analysis,and the load flows of transmission lines can be presented as the function of generation outputs.The arrangement of each generator output is optimized using linear programming method.Then a novel method is proposed to model load correlations at different buses.The combination of correlation analysis,Monte Carlo sampling and regression method contribute much to model load correlations.The security constraint generation dispatch model is validated with IEEE RTS 24-bus system,and impact of security constrained generation dispatch on transmission network utilization is quantitatively analyzed.Results show that with consideration of security constraint,generation dispatch becomes more reasonable without failure problems such as line overload occurring.The load correlation model is validated using the actual transmission system of C ity T in C hina with historical data of 2014,and the impact of load correlations on transmission network utilization is quantitatively analyzed.Results show that correlations among loads affect the evaluation of transmission network utilization significantly.Therefore,simulation results obtained from the improved probabilistic load flow algorithms can preferably reflect the operation status of actual system.At last,the transmission system of C ity T in 2020 is specifically simulated.The whole index system of future transmission network utilization is calculated and the transmission planning scheme is evaluated.The effectiveness and applicability of proposed methods in this paper are validated and the simulation results will have significant effects on transmission planning. |
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