A method for controlling a wind turbine power system connected to a power grid, the power system having a plurality of clusters of power subsystems, each of the power subsystems including a generator comprising: a generator stator connected to a stator power path connected to the power grid for supplying power to the power grid, and a generator rotor connected to a converter power path for supplying power to the power grid, wherein the converter power path comprises: a power converter coupled to the rotor; a two-winding transformer comprising a primary winding connected to the power grid and a secondary winding connected to the power converter, the method comprising: receiving, by a controller, a reactive power instruction and a measured reactive power from the generator; generating a reactive power error signal by the controller based on a difference between the reactive power instruction and the measured reactive power; receiving the reactive power error signal by a reactive power regulator; generating a voltage instruction by the reactive power regulator based on the reactive power error signal; generating a voltage droop signal by a droop controller based on a reference reactance and a voltage at a point of common coupling; generating a predetermined range according to the voltage droop signal; using the predetermined range for limiting the voltage instruction; generating, by the controller, the voltage error signal according to at least one of the limited voltage instruction or a measured terminal voltage of the generator and the voltage droop signal; and generating a reactive current instruction for the converter power path by a voltage regulator based on the voltage error signal. a generator stator connected to a stator power path connected to the power grid for supplying power to the power grid, and a generator rotor connected to a converter power path for supplying power to the power grid, wherein the converter power path comprises: a power converter coupled to the rotor; a two-winding transformer comprising a primary winding connected to the power grid and a secondary winding connected to the power converter, the method comprising: receiving, by a controller, a reactive power instruction and a measured reactive power from the generator; generating a reactive power error signal by the controller based on a difference between the reactive power instruction and the measured reactive power; receiving the reactive power error signal by a reactive power regulator; generating a voltage instruction by the reactive power regulator based on the reactive power error signal; generating a voltage droop signal by a droop controller based on a reference reactance and a voltage at a point of common coupling; generating a predetermined range according to the voltage droop signal; using the predetermined range for limiting the voltage instruction; generating, by the controller, the voltage error signal according to at least one of the limited voltage instruction or a measured terminal voltage of the generator and the voltage droop signal; and generating a reactive current instruction for the converter power path by a voltage regulator based on the voltage error signal. a power converter coupled to the rotor; a two-winding transformer comprising a primary winding connected to the power grid and a secondary winding connected to the power converter, the method comprising: receiving, by a controller, a reactive power instruction and a measured reactive power from the generator; generating a reactive power error signal by the controller based on a difference between the reactive power instruction and the measured reactive power; receiving the reactive power error signal by a reactive power regulator; generating a voltage instruction by the reactive power regulator based on the reactive power error signal; generating a voltage droop signal by a droop controller based on a reference reactance and a voltage at a point of common coupling; generating a predetermined range according to the voltage droop signal; using the predetermined range for limiting the voltage instruction; generating, by the controller, the voltage error signal according to at least one of the limited voltage instruction or a measured terminal voltage of the generator and the voltage droop signal; and generating a reactive current instruction for the converter power path by a voltage regulator based on the voltage error signal. receiving, by a controller, a reactive power instruction and a measured reactive power from the generator; generating a reactive power error signal by the controller based on a difference between the reactive power instruction and the measured reactive power; receiving the reactive power error signal by a reactive power regulator; generating a voltage instruction by the reactive power regulator based on the reactive power error signal; generating a voltage droop signal by a droop controller based on a reference reactance and a voltage at a point of common coupling; generating a predetermined range according to the voltage droop signal; using the predetermined range for limiting the voltage instruction; generating, by the controller, the voltage error signal according to at least one of the limited voltage instruction or a measured terminal voltage of the generator and the voltage droop signal; and generating a reactive current instruction for the converter power path by a voltage regulator based on the voltage error signal.