Probabilistic load flow analysis considering the correlation for microgrid with wind and photovoltaic system

With the distributed energy system widely used, quite a few microsources have been connected to the microgrid recently. Due to the randomness, uncertainty and correlation of microsources, the models of typical power flow calculation are not suitable for the microgrid. A probabilistic load flow analysis is proposed based on third-order polynomial normal transformation(TPNT) combining three-point estimate method in this paper. And the probabilistic models of microsources, such as wind energy system, PV/wind hybrid system, are established according to the control characteristics and various random factors. The correlation of input random variables in the same area is also taken into consideration. In order to deal with input random variables, the TPNT is used to transform correlated non-normal random variables into uncorrelated normal random variables. Then the independent input variables can be estimated by three-point estimate method and calculated by deterministic power flow algorithm. The proposed method is tested in a typical microgrid system containing multi-type microsources. By comparing three different cases, the simulation results show that the proposed method is generic, effective and correct. Besides, the microgrid system consisting of multi-type microsources can obtain the optimal performance characteristics.