The shafting systems of hydropower units work as the core component for the conversion of water energy to electric energy and have been running for a long time in the hostile hydraulic–mechanical–electrical-coupled environment—their vibration faults are frequent. How to quickly and accurately identify vibration faults to improve the reliability of the unit is a key issue. This study proposes a novel shafting vibration fault identification framework, which is divided into three coordinated stages: nonlinear modeling, signal denoising, and holographic identification. A nonlinear dynamical model of bending–torsion coupling vibration induced by multiple excitation vibration sources of the shafting system is established in the first stage. The multi-stage signal denoising method combines Savitzky–Golay (SG) smoothing filtering, singular value decomposition (SVD), and variational mode decomposition (VMD). SG-SVD-VMD is used for the guide bearing the vibration signals in the second stage. Further, the holospectrum theory is innovatively introduced to obtain the holospectra of the simulated and measured signals, and the shafting vibration faults of the real unit are identified by comparing the holospectrum of the measured signal with the simulated signal. These results show that the shafting nonlinear model can effectively reflect the vibration characteristics of the coupled vibration source and reveal the influence and fault characteristics of each external excitation on the shafting vibration. The shafting vibration faults of operating units can be identified by analyzing the holospectra of the shafting simulation signals and measuring the noise reduction signals. Thus, this framework can guide the safe and stable operation of hydropower units.
The hydro-turbine governing system (HTGS) and shafting system are mutually coupled. However, the interaction between them has always been neglected. This paper aims to explore the stability and sensitivity of the governor control parameters to the HTGS and shafting system and make the optimal control of the stable operation for the hydro-turbine generator unit(HTGU). First, a novel HTGU motion equation is proposed, which can make connections between the HTGS and the shafting system of the HTGU. And on this basis, the nonlinear coupling mathematical model of the HTGS and the shafting system is established. According to the nonlinear mathematical model, the sensitivity of the governor control parameters on the operating stability of the HTGU is obtained. Then, a multi-objective governor control parameters optimization strategy is proposed. Furthermore, the chaotic-dominated sorting genetic algorithm II(NSGA-II) and multi-objective evolutionary algorithm based on decomposition(MOEAD) were introduced to obtain the optimal control parameter and mutually verify the effectiveness of the optimization effect. Finally, the nonlinear dynamic characteristics of HTGU under optimal control were revealed. The simulation results show that the rotation speed deviation and shafting system vibrations are sensitive on the PID parameters in some ranges and the stable region will be decreased when considering the shafting system vibrations. The multi-objective PID parameter optimization strategy shows good control performance on the nonlinear dynamic characteristics of the HTGU. The shafting system vibrations excited by the coupled vibration sources are quasi-period in 3D space. In addition to this, these results and the optimization strategy can provide some bases for the design and stable operation of the HTGU.
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