In order to rationally plan offshore wind farm(OWF) and improve the economics of OWF investment and operation

it is necessary to study the planning of offshore wind farm turbines and collection networks. For the OWF collection system using AC grid-connected mode

a coordinated optimization planning model of wind turbines(WTs) and collection network is established with the goal of maximizing the annual expected profit of the OWF collection system. Meanwhile

the decision variables are the WTs' locations and capacities

the voltage level and topological connection of the collection network

the collection cable capacities

the locations of the offshore platforms and the transformer capacities. In the model

the wake effect model considering regional wind directions is used to accurately reflect the wake effect between different WTs. In order to solve the coordinated planning model

by using the Benders decomposition method

the original mixed integer nonlinear programming model is decomposed into the master problem of mixed integer linear programming model and the sub-problem of quadratic programming model; moreover

the optimal coordinated planning scheme is efficiently obtained through alternative iteration solution

and a method of using polyline to handle cross submarine cables is proposed to improve the efficiency of model solution. Finally

two practical OWFs with installed capacity of 200 MW and 1 000 MW are analyzed. The results show that

compared with the centralized solution and other methods

the proposed method has higher solution efficiency

and the obtained OWF planning scheme has higher economy and reliability.