Study On The Application Of Power Flow Calculation Considering Load Model In Low Voltage Control

In recent years,with the acceleration of urban and rural development in China,electricity consumption in rural power grids has been increasing year by year.However,rural power grids have features such as multiple points,wide coverage,long lines,strong seasonality,and insufficient reactive power.As a result,low-voltage problems are widespread.Seriously affected the life and production of farmers.For this reason,it is particularly important to systematically propose low-voltage treatment schemes for rural distribution networks.Power flow calculation is the basis of distribution system analysis.In the process of low-voltage treatment of rural distribution network,obtaining voltage distribution and distribution of power flow through power flow calculation is the premise of low-voltage control scheme.The selection of the load model is one of the important factors affecting the power flow calculation results.Therefore,it is necessary to establish a suitable load model in the load flow calculation so that the calculation result is more in line with the situation of the rural distribution network,and then a suitable low-voltage treatment plan is selected according to the load flow calculation results.Firstly,this paper establishes the load model of the distribution system during the study of the low-voltage control scheme of the rural distribution network.By considering the voltage static characteristics of load,the power function model,polynomial model and IEEE standard load model are introduced.At the same time,mathematical models have also been established for distributed power in distribution networks.Secondly,based on the Newton-Raphson method load flow calculation,the load model is introduced into the distribution network load flow calculation.The current traditional power flow calculation method is improved so that the power imbalance in the Newton-Raphson method can change with the voltage during the iteration process.The traditional NewtonRaphson method tends to use the load as a PQ node in the load flow calculation.After the load model and the distributed power supply model are introduced,the load's node type also changes,and is divided into PQ nodes and PV nodes according to the load types.PI node and PQ(V)node,where the load model at each node adopts a polynomial model composed of constant power load,constant current load,and constant impedance load.Through the example analysis,it is shown that in load flow calculation,different load models will affect the voltage of the system node,and the addition of distributed power supply can play the role of controlling the low voltage phenomenon.Since there are a large number of three-phase asymmetrical loads in the rural distribution network,it is necessary to calculate the three-phase power flow of the distribution network.Therefore,for the traditional Newton-Raphson three-phase power flow calculation,there is a large amount of calculation,low efficiency,and can not deal with the different types of load in the actual distribution network,proposes a three-phase modified Newton-Raphson method considering the type of load.The algorithm also adopts the load polynomial model.On the basis of the traditional three-phase Newton-Raphson method,the Jacobian matrix is simplified to split,and the split matrix is solved,thereby improving the threephase power flow calculation efficiency.The feasibility and effectiveness of the algorithm are verified by calculation examples.The results show that the algorithm can handle three-phase distribution network systems with different load types,and the reduction of the constant power load proportion makes the system node voltage increase.Finally,taking Huanghua Power Grid of Qinghai Province as an example,the traditional Newton-Raphson method is used,the Newton-Raphson method considering the load model and the improved three-phase Newton-Raphson method are used for power flow analysis to obtain the node voltage of a typical line and Trend distribution,the weak voltage area is found out,and the corresponding pressure regulation measures are proposed.The most reasonable lowvoltage control solution was selected through simulation analysis and analysis.The result of the case study shows that the improved three-phase Newton-Raphson method for power flow calculation is more helpful to find a suitable treatment plan in the low-voltage control of rural distribution networks.For the low-voltage problem in Juhuzha Village of Huanghua Power Grid Angsi Road,a more reasonable solution is to shift the heavy load.