A Novel Smooth Switching Method Between Voltage Source and Current Source of DFIG Based Wind Turbine

Doubly-fed wind turbines present current source characteristics under vector control, and the phase-locked loop section relies on grid phase information, which is suitable for operation under strong grid; and present voltage source characteristics under virtual synchronous control, which can provide frequency and voltage support for the grid, which is more suitable for operation under weak grid. In order to meet the needs of grid operation under different short circuit ratios, it is of great practical significance to study the control mode switching of doubly-fed wind turbines. This paper proposes a smooth switching control strategy for doubly-fed wind turbine voltage-current source dual-mode operation, which realizes the smooth switching of phase and current commands through the joint action of controller state following and numerical soft starter, and effectively suppresses current impact and power fluctuation in the switching process of doubly-fed wind turbine operation mode. Finally, the effectiveness of the proposed control strategy is verified by theoretical analysis and simulation results.