The Method Of Probabilistic Power Flow Calculation Of Three-phase Asymmetric Islanded Microgrid Of Droop Control

Microgrid is a small generation, distribution and utilization power system, which is made up of distributed sources, energy storage systems, energy conversion device, load and so on, what is more, microsource is probabilistic, uncertain small output and so on, which makes the structure of islanded microgrid is different from traditional grid, and it is more serious in islanded mode. In order to provide theoretical basis for the distribution of voltage and power of the islanded microgrid, researching the steady-state model and power flow calculation method fitting for islanded microgrid is the main body in this paper.Considering the output power of microsource, the microsource can be divided into two categories in this paper in the first place: controlled micro sources and uncontrolled micro sources.Controlled microsource, such as batteries, gas turbine, etc, is seen as sagging nodes considering the changes of frequency, and the new output of microsource is replaced considering new voltage and frequency. Uncontrolled microsource, such as solar, tidal power, etc, is seen as PQ node and can be simulated considering its randomness.This paper adopts the improved Newton-Raphson method to calculate the power flow according to the physical truth of islanded microgrid. The algorithm adopts Jacobi matrix of all nodes without the balance nodes that can modify the system frequency through introducing frequency calculation module to the Jacobi matrix. Finally the accurate trend value can be obtained by repeated iteration. The three-phase power flow calculation is needed for actual system,sequence component method is chose in this paper, in which the method of power flow calculation of positive sequence network use the improved Newton-Raphson method, while the negative and zero sequence choose gauss method for power flow calculation. For probabilistic power flow calculation based on deterministic trend calculation, this paper adopts the Monte Carlo method to simulate the output for the uncontrolled microsource and some special load, then power flow can be repeatedly calculated according to the multiple analog power value. At last, you can get the probability characteristics of parameters of islanded microgrid through statistical analysis of the results, such as voltage, frequency. The conclusion verifies the correctness of the probabilistic power flow algorithm based on the droop-control islanded microgrid using IEEE33 node system through writing the procedure of probabilistic flow calculation of three-phase islanded mIcrogrid in MATLAB.