In the offshore wind power transmission system through the AC submarine cable（SC）

as the scale of the offshore wind farm gradually increases

the transmission distance of the AC submarine cable continues to increase.Due to the large charging power of the SC

there are many problems in the actual offshore wind power connection project

such as excessive reactive power injection at the grid-connected points of offshore wind farms

over-voltage and over-current carrying capacity along the SC

and over-voltage on the high-voltage side of the offshore substation.In response to the above problems

this paper establishes a mathematical model for the transmission system of offshore wind farms via a 220 k V AC SC

and analyzes the wind power transmission system based on the principle of layered division of reactive power compensation.Under the condition of voltage and current limitation along the cable

the high resistance value of compensation is determined.High reactance and SVG are installed on land to make the reactive power exchange between the wind power delivery system and the land AC network zero.When the SVG capacity is minimum

onshore high impedance value connected to the system is given.Combined with a specific domestic project

the recommended reactive power configuration plan is calculated.