Abstract: A wind power generation system and a control method thereof are provided herein. The wind power generation system includes a doubly-fed generator, a generator-side converter, a grid-side converter and an auxiliary converter. The doubly fed generator includes a stator winding and a rotor winding. The stator winding is coupled to a grid. The generator-side converter is coupled to the rotor winding. The grid-side converter is coupled between the generator-side converter and the grid. The auxiliary converter includes a first side and a second side. The first side is coupled to the stator winding. The second side is coupled between the generator-side converter and the grid-side converter. The generator-side converter, the grid-side converter and the auxiliary converter use the same DC bus.

Abstract: A wind power generation system and a control method thereof are provided herein. The wind power generation system includes a doubly-fed generator, a generator-side converter, a grid-side converter and an auxiliary converter. The doubly fed generator includes a stator winding and a rotor winding. The stator winding is coupled to a grid. The generator-side converter is coupled to the rotor winding. The grid-side converter is coupled between the generator-side converter and the gird. The auxiliary converter includes a first side and a second side. The first side is coupled to the stator winding. The second side is coupled between the generator-side converter and the grid-side converter. The generator-side converter, the grid-side converter and the auxiliary converter use the same DC bus.

Abstract: A control device and control method of power conversion unit applied to a three-phase AC grid. The control device includes detection unit, current detection unit, and signal processing unit. The detection unit detects three-phase voltage signal of the three-phase AC grid and calculates and generates negative sequence reactive current given signal. The current detection unit detects current of the power conversion unit to output feedback current signal. The signal processing unit receives the negative sequence reactive current given signal, positive sequence current given signal, and the feedback current signal to output modulation signal. The power conversion unit is electrically coupled to the signal processing unit and the three-phase AC grid. The power conversion unit absorbs negative sequence reactive currents from the three-phase AC grid according to the modulation signal when the three-phase voltage signal is unbalanced to reduce negative sequence voltage at output terminal of the power conversion unit.

Abstract: A control device and control method of power conversion unit applied to a three-phase AC grid. The control device includes detection unit, current detection unit, and signal processing unit. The detection unit detects three-phase voltage signal of the three-phase AC grid and calculates and generates negative sequence reactive current given signal. The current detection unit detects current of the power conversion unit to output feedback current signal. The signal processing unit receives the negative sequence reactive current given signal, positive sequence current given signal, and the feedback current signal to output modulation signal. The power conversion unit is electrically coupled to the signal processing unit and the three-phase AC grid. The power conversion unit absorbs negative sequence reactive currents from the three-phase AC grid according to the modulation signal when the three-phase voltage signal is unbalanced to reduce negative sequence voltage at output terminal of the power conversion unit.

Abstract: A phase locking system for a three-phase alternating current (AC) electric grid and a method thereof are disclosed. The method includes: receiving a three-phase voltage of the AC electric grid and converting the three-phase voltage to a two-phase voltage signal, each of which including a positive and a negative sequence components; obtaining a pure positive sequence component by subtracting the negative sequence component from the voltage signal of each phase and using ??/dq coordinate transformation and low-pass filtering, and phase locking the pure positive sequence component; and obtaining an error signal by subtracting a disturbance variable and subsequently subtracting the positive sequence component from the voltage signal of each phase, wherein the disturbance variable includes the negative sequence component, and obtaining a signal including the negative sequence component by performing a ?-?/d-q coordinate transformation on the error signal and adjusting the error signal through a regulator.