The invention discloses a permanent magnetic direct-drive type
offshore wind power plant grid-connected
system topology structure and a control method thereof. A grid-connected
system comprises a
DC bus current collection type
wind power plant, a
wind field network-side converter
station, a dual-stage boost
transformer, an offshore rectification
station, a
seabed DC cable, a
shore inversion
station, a grid-connected side boost
transformer and a land
power grid which are successively connected, wherein the
DC bus current collection type
wind power plant employs a
DC bus current collection topology structure and comprises multiple groups of wind turbines which are successively connected, a permanent magnetic synchronous generator, a
machine-side
rectifier and a DC
bus for current collection. The control method is that the
machine-side
rectifier employs dual-closed-
loop control of a rotating speed outer loop and a current
inner loop, the
wind field network-side converter station employs dual-closed-
loop control of a
voltage outer loop and the current
inner loop, the offshore rectification station employs control of fixed AC voltages and fixed frequencies, and the
shore inversion station employs dual-closed-
loop control of fixed DC voltages and fixed reactive power. According to the invention, multi-
machine parallel-connected operation can be realized, the
electric energy conversion efficiency is improved, and the grid-connected AC
harmonic quantity is reduced.