A Simplified Stator Frequency and Power Control Method of DFIG-DC System without Stator Voltage and Current Sensors

The primary objective of the grid connected DFIG-DC system is to achieve the accurate control of stator frequency and active power. In this letter, a simplified power control method is proposed by just controlling the magnitude of the rotor current vector, which can avoid the stator voltage and current sensors. The stator active power is calculated by the product of dc voltage and dc current. The stator frequency is simply controlled by the rotating speed of the rotor current vector, which is achieved through a given rotating frame. Furthermore, the parameter dependence and dc sampling offset problems can be eliminated because the voltage model or current model, which are usually used for acquiring stator frequency and stator flux angle, can be avoided. Therefore, the robustness and stability of the stator frequency and power control can be improved. Finally, experiments based on a 1 kW DFIG-DC setup are carried out to verify the proposed method.