Abstract
When the asymmetric fault occurs in power grid, it will cause the oscillation of the electromagnetic torque of the doubly-fed induction generator(DFIG). The oscillation of the electromagnetic torque will cause the torsional vibration of the drive chain, and the long-term torsional vibration will shorten the service life of DFIG. The analysis shows that the positive and negative sequence current components generated by DFIG terminals are the main factors that cause electromagnetic torque oscillation when the asymmetric faults occur. Therefore, the suppression of positive and negative sequence current components is the key to achieve active control of torsional vibration of drive chain, the traditional PID control can only adjust the direct-current(DC) component without static error, and cannot suppress the negative sequence alternating-current(AC) component. In this paper, based on the traditional PID regulator, the resonance(R) current regulator with the specific frequency is incorporated into the grid-side converter(GSC) to form the PID-R current controller. The PID-R current controller can realize accurate and effective control of the positive and negative sequence components in the forward rotation synchronous speed rotating coordinate system without decomposing the positive and negative sequence components, and can actively suppress the electromagnetic torque oscillation, thereby realize the active control of the drive chain torsional vibration. MATLAB/Simulink verifies the effectiveness of PID-R current controller.
Highlights
Doubly-fed induction generator (DFIG) has become the mainstream of wind power generation
Because the duration of asymmetric fault is usually short and the inertia time constant of wind turbine is large, it can be considered that the speed and aerodynamic torque of wind turbine are basically unchanged. It can be seen from Equation(17) that the main factor that causes the torsional vibration of the drive chain under the asymmetric fault of the power grid is the electromagnetic torque of the DFIG
Is(%), Ir (%), and Vdc(%) in the table are the current unbalance degree and bus voltage unbalance degree caused by asymmetric fault of power grid, Te and P are the oscillation of electromagnetic torque and active power when the grid asymmetric fault occurs
Summary
Doubly-fed induction generator (DFIG) has become the mainstream of wind power generation. INDEX TERMS Asymmetrical power grid fault, drive chain torsional vibration, DFIG, electromagnetic torque, negative sequence current.
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