A Point Estimation Method For Stochastic Optimal Scheduling Of Micro-grid

With the rapid development of science and technology and the industry,the traditional energy and the environment meet tremendous pressures and challenges.Micro-grid as an important part of the smart grid,in recent years has caused widespread concerns.Microgrid mainly connected with the power user, has been highly valued by its low cost and low voltage and low pollution.The micro-grid, which is a new type of energy network supply and management structure, provides a channel for distributed generations to access the low voltage distribution network. Various variables make tremendous impact to the optimize operation of the micro-grid.How to evaluate these uncertainties impact on the economic operation of micro-grid deserves deeply study.The uncertainty factors of wind and solar output power and intermittent load makes micro power flow calculation with random characteristics.With probability density functions of the intermittent micro-sources,an effective calculation methodology for probabilistic power plows fitting the micro-grids is established, in which point estimation method is adopted as to simulate stochastic performance of the intermittent micro-sources.According to the probability density function of the distributed power output and the probability distribution of load demand and structural its estimate point, the distributed estimated point embedded in backward substitution method, establish random flow calculation to obtain the mean and standard deviation of the data reliability assessment to estimate the micro probability grid system node voltages and branch power density function.A corresponding program is developed for probabilistic power flow computation, which presents referential basis for further reliability assessment and optimal control of the micro-grids.Finally, in order to verify the superiority of this point estimation method, the Monte Carlo simulation is used in the calculation of the random flow, and fewer and faster processing through a practical case study method to calculate point estimates.The point estimate method is used to deal with the uncertainty in load demand and output power of solar and wind units.The objective function and constraints related to the operation of micro-grid are formulated and mathematical model is established.The cumulative distribution functions(CDFs) and PDFs for total operating cost are accurately obtained by the Cornish-Fisher series expansion. Through a practical case,studies the advantages and disadvantages of three point estimation method, the results show that although the frequency of flow calculation more than two point estimate, but the speed and accuracy of flow calculation superior to the two point estimate.In order to overcome the defect that the algorithm depends strongly on the parameter, it this paper uses the andomness, ergodicity and regularity of the chaos to adjust the firefly algorithm parameters. By example show the advantages of the proposed algorithm and the actual significance of the proposed mode.