Research On Stochastic Power Flow Calculation For Microgrids

With the continuous advancement of technology, more and more energy and natural resources have been consumed. As an important developing trend of power system,microgird is extremely important for solving the energy problem and maximize the distributed generation's usefullness. Also, microgird can assemble a variety of DGs to provide electrical energy for the local loads, and ensure that all loads work normally in any cases, which can handle the islanded operation problem of DG.It is need to consider the stochastic when analyzing the operating characteristics of microgird because of the probabilistic output power of the microsources. So it is very significant to research and analyze the stochastic power flow of microgrid. The microgrid model containing microsources module, energy storage system, and loads is studied in this paper first. Then based on a comprehensive comparative analysis of existing stochastic power flow methods, the method combines the cumulant and Gram-Charlier expansion is especially studied and applied in the stochastic power flow calculation for microgrid.The wildly used method based on cumulant and Gram-Charlier expansion is faster and more reliable. While the method must ensure the kurtosis and skewness coefficient in expansion near to 0, which is not satisfied in the microgrid because of the probabilistic output power of the microsources always fluctuating sharply. Aiming at this problem, an improved stochastic power flow algorithm for microgrid is presented in this paper. This approach handles the normally and discretely distribution input variables separately, and employs the method to solve the discrete distribution variables, which can get the probability distribution accurately.Stochastic power flow calculation and analysis is made to show the operating characteristics for microgrid in this paper, furthermore the impact of microsources and energy storage system on microgrid is analyzed. Both the microsources with more little output power or more different kinds and the energy storage system can inhibit the impact of microsources'probabilistic output power on the fluctuation of voltage for microgrid. Besides, the equal model of microgrid connecting to the network is researched.