Enclosed is an active and reactive coordination control method for permanent-
magnet direct-driven wind turbines in the low-
voltage ride-through process. Two different control strategies are employed for a grid side converter according to amplitude change of
power grid voltage: when the
power grid voltage is in a
normal state, the grid side converter is in an active-priority maximum power tracing
control mode so that the wind turbines capture wind energy to the maximum extent; when the
power grid voltage is beyond the
normal range, the grid side converter is in an active priority
control mode so that the dynamic reactive current which is injected into an
electricity system meets the requirements of grid combining. An engine side converter is in a direct-
current voltage control mode based on rotor
energy storage, power unbalance of the direct-current side of the engine side converter is relieved and the direct-
current voltage is stabilized by utilizing the self rotating speed of the permanent-
magnet direct-driven wind turbines and the change of the
kinetic energy. The active and reactive coordination control for the wind turbines before or after the sudden change of the power
grid voltage is realized according to the amplitude change of the power
grid voltage, the fluctuation of the direct-current
bus voltage is restrained by releasing or storing the rotor
kinetic energy, so that the low-voltage ride-through capability of the permanent-
magnet direct-driven wind turbines is improved, reactive power support is rapidly and accurately provided for the power grid, and certain support is given to restoration of the power
grid voltage.