Design of auxiliary power supply in pitch controller of large-scale wind turbine

Pitch controller is a very important controller in large-scale wind turbine. Its power usually comes from the inner three-phase ac bus of the wind turbine. However, the ac bus voltage is often higher than 400 V, which is far beyond the necessary voltage of the pitch controller. Therefore, the pitch controller must have its own auxiliary power supply to operate normally. This paper discusses a high voltage flyback converter as such auxiliary power supply. The transformer in this converter is with high voltage transfer ratio and with the special physical structural design to reduce the leakage inductance. To greatly improve the cross-regulation capability of the outputs, multiple output sensing technology in voltage feedback loop is used here. In addition, this paper also discusses the design of protection circuit and transformer primary snubber circuit. The experimental results of a prototype with three outputs verify the practicability of this design.