Numerical Investigation of Semi-active Torsional Vibration Control of Heavy Turbo-generator Rotor using Magnetorheological Fluid Dampers

Background For the continuous operation of the power plant and to prevent any economic or fatal damages, the torsional vibration control of the large turbo-generator rotor is required. Compared to the flow mode dampers, the shear mode magnetorheological fluid dampers are less efficient in regulating the torsional vibrations of the large turbo-generator rotor because of the complicated configuration and low damping ability. Purpose This theoretical study explains how magnetorheological (MR) fluid dampers can be used to control torsional vibration of the turbo-generator rotor. A theoretical analysis is conducted to compare the damping efficiency of the MR damper under constant and variable magnetic fields. Methods The dq0 model is used to simulate the electromagnetic torque of the generator during multiple electrical failures. The turbo-generator rotor is simulated using the finite element method. MR fluid dampers are attached to the rotor's different coupling elements. For designing the dampers, the modified Bouc-Wen model is used. In MATLAB, the coupled finite element equations are solved using Newmark-beta integration method. Results The peak amplitude of torsional vibrations in element 35 reduce by 1-60 percent for various electrical faults using passive MR dampers and 10-46 percent using semiactive MR dampers. The peak amplitude of torsional vibrations in element No 74 reduces by 1-55 percent for various electrical faults using passive MR dampers and 7-50 percent using semiactive MR dampers. Conclusions During various electrical failures, the most severe torque evolved is three phase fault, followed by the line to ground, followed by mal-synchronization fault and line to line fault. The torsional vibrations produced on turbo-generator rotor due to this variation in electromagnetic torque of the generator and the numerical results show the significant reduction in the torsional vibration of the rotor when MR fluid dampers are used.