A wind turbine system includes a wind turbine and switching devices. Each switching device is for stabilizing an electric output of a coil of the wind turbine, and includes a voltage converter circuit, a switch circuit electrically connected between the voltage converter circuit and an output interface, and a controller circuit. The controller circuit is configured to calculate an input electric power of input electricity into the voltage converter circuit, to calculate an output electric power of output electricity outputted by the voltage converter circuit, and to control the switch circuit to operate in one of a closed state and an open state according to the input electric power and the output electric power.