Aimed at the problem of slight low node voltage at the end of feeder of in low voltage distribution network

the coordinated optimization calculation model for distributed reactive power compensation and line diameter expansion is proposed.The investment cost for installing reactive power compensation device and replacing line and the economy efficiency of reducing network loss are comprehensively considered in the objective function.The constraints include various operation constrain of distribution network

upper and lower constraints of compensation capacity of the reactive power compensation point and expansion cross section area of line path.The convex relaxation technology is used to process continuously the integer variables in the optimization model and the number of integer variables is reduced by the characteristics of the problem.The branch with high voltage loss is selected as the candidate line of diameter expansion line in accordance with flow calculation of low voltage distribution network and

at the same time

all the load is taken as candidate reactive power compensation point

and the coordinate optimization proposal is obtained of distributed reactive power compensation and line diameter expansion is obtained by the calculation.A certain actual low voltage distribution network is taken as an example.It is verified through the calculation result that the coordinated optimization proposal obtained by the proposed method has higher economy efficiency and better voltage quality than those of pure reactive power compensation proposal.