Probabilistic Load Flow Calculation Considering Correlation Between New Energy Power Generation Based On Node Analysis Method

The output power of new energy power generation has strong randomness, and the output power of new energy power generation which in the same region has some correlation, if large-scall new energy power generation connects to power grid, it will have a great impact on the safe operation of power grid. Probabilistic load flow calculation can consider various uncertain factors, the probabilistic characteristics of output variables can be achieved by the probabilistic characteristics of these various uncertain factors, so it has much referential value for the planning and design of power system and the arrangement of power system operation mode. To further improve the efficiency and expand the application range of probabilisitc load flow calculation, a kind of probabilistic load flow calculation considering correlation between new energy power generation based on node analysis method is proposed in the paper.(1) The probability analysis and the correlation evaluation of the output power of new energy power generation are realized. The experience distribution estimation method is introduced, the cumulative distribution function of the output power of new energy power generation can be fitted by the experience distribution estimation method based on the output power historical data of new energy power generation. the Copula theory is introduced, the concrete steps of the correlation evaluation of the output power of new energy power generation through the squared Euclidean distance method to choose the proper Copula function is elaborated.(2) The probabilistic load flow calculation model based on node analysis method is established. The effects of node voltage variations by P V node active power injection variations and the effects of node voltage variations by PQ node power injection variations are considered seperately. When the effects of node voltage variations by PV node active power injection variations are considered, the relationship model between PV node active power injection variations and node voltage variations can be established based on the linear relationship between PV node voltage real part variation and imaginary part variation; When the effects of node voltage variations by PQ node power injection variations are considered, the relationship model between PQ node power injection variations and node voltage variations can be established based on the features of PV node voltage variation is close to 0 and node voltage is maintained at per unit value 1 under normal system operation.(3) The probabilistic load flow calculation model considering correlation between new energy power generation based on node analysis method is established. The correlation of the output power of new energy power generation can be processed by Cholesky decomposition method, then the probabilistic load flow calculation model based on node analysis method can be amended, and the relationship model between branch power flow variations and node power injection variations can be deduced. the proposed probabilistic load flow calculation considering correlation between new energy power generation based on node analysis method is tested in IEEE-14 bus system and IEEE-118 bus system, the results indicates that the proposed method is effective.