Dynamic Reactive Power Optimization Of Distribution Network Considering Distributed Generation Power Uncertainty

With the global energy shortage and environmental destruction,renewable energy,with its advantages of rich resources,clean and pollution-free,has been paid more and more attention by the power industry,especially the proportion of distributed power generation connected to the grid is increasing.However,the output of distributed power supply has strong randomness and correlation,and its access not only directly changes the power distribution of the original system,but also has a great impact on the system loss and voltage quality,which brings a lot of uncertainty to the system operation.Therefore,the traditional static reactive power optimization is not competent for such a complex system running state.Aiming at this problem,the paper studies the dynamic reactive power optimization of distribution network considering the power uncertainty of distributed generation,centering on the security and economy of the system operation.Firstly,several kinds of distributed power sources are briefly introduced,and the fan and photovoltaic with uncertain output power are selected as distributed power sources for grid-connection research.Based on the ideal model of grid connection of distributed power generation,the influence of access location and capacity of distributed power generation on voltage and network loss of distribution network is analyzed by numerical simulation.Secondly,aiming at the uncertainty of wind power and photovoltaic output and load,the probability model of their power is determined according to the output characteristics of wind power and photovoltaic as well as the distribution characteristics of load.In order to deal with the correlation between random variables and obtain the probability density or cumulative distribution of output variables,an improved three-point estimation method based on Nataf transform and Gram-Charlier series expansion is proposed.The calculation accuracy and efficiency of the algorithm are verified by IEEE33 system,and the influence of the output correlation between distributed power sources on the system operation is analyzed.Then,on the basis of the static reactive power optimization model,the dynamic reactive power optimization model of the distribution network,which takes into account the adjustment cost of the control equipment,is established with the goal of minimizing the total network loss and voltage offset of the system throughout the day,considering the action times constraint of the control equipment.With the cooperation of the optimal segmentation method and the improved particle swarm optimization algorithm,the constraint conditions of the control variables are processed and the model is solved.Through the simulation analysis of the improved IEEE33 system,it is proved that the dynamic reactive power optimization can effectively improve the safety and economy of the system under the restriction of the number of control equipment movements.At the same time,it is verified that the improved particle swarm optimization algorithm has higher computational accuracy and efficiency.Finally,in view of the distributed power output and load forecast errors,considering reactive power regulation characteristic of distributed power supply,according to the real-time updating of information output and load fluctuation,at present,on the basis of dynamic optimization scheme,with the total voltage prediction deviation and minimum network loss as the goal,set up the model of real-time reactive power optimization based on dynamic partitioning.The accuracy and rapidity of voltage regulation are verified by the simulation analysis of a numerical example,which further improves the safety and economy of the system operation.