To effectively judge the vibrational stationary state of hydropower units, the whirling characteristics of the rotor vibration and the evaluation method of stability of shaft vibration were studied. The theoretical expression of instantaneous whirling velocity was derived, and the characteristic parameters of whirling velocity were analyzed. A holographic whirling velocity analysis method for shaft vibration was proposed. The whirling characteristics indicators and vibration stability evaluation index of shaft vibration were established. Finally, the theory of this paper was applied to the shaft vibration data analysis of Zhejiang Xianju pumped storage power station. The key characteristic indicators of vibration were extracted and the shafting stationary was evaluated. The results show that the established characteristic indicators have good performance in evaluating the stationary of shaft vibration, and have broad application prospects for the monitoring and performance evaluation of actual hydropower units.

The health status assessment of hydraulic turbines is a necessary task for achieving health management of hydraulic turbines, and is a key step in achieving condition based maintenance of hydraulic turbines. Considering the uncertainty and fuzziness of the obtained representation information of the health status of hydraulic turbines, a combination of qualitative and quantitative indicator systems was constructed. The health status of hydraulic turbines was defined as 5 states and transformed into cloud droplets using language scale functions. The evaluation of the health status of hydraulic turbines was achieved through cloud distance. The effectiveness of the health status evaluation model was verified using a certain type of hydraulic turbine as an example, which provides a solid foundation for equipment health management of hydraulic turbine.

At present, the issue on the influence of mixed arrangement of variable and constant speed units on the load rejection transition process under the complex water delivery system with multi-units sharing multi-tunnels is scarce. Based on the transient flow theory of one-dimensional pipeline, this paper established the mathematic model of hydraulic transition process of variable-constant speed pumped storage units that four units share two tunnels in the diversion system and one tunnel in the tailrace system by using the characteristic method, and discussed the influence of the mixed arrangement of variable and constant speed units on regulation guarantee parameters under the load rejection condition by combining with practical engineering examples. The results show that regulation guarantee parameters during the load rejection transition process under the layout of two variable speed units sharing one diversion hole are safer than those under the layout of variable speed units sharing different diversion holes in the region with higher power generation efficiency.

With the transformation of the southwest power grid with a high proportion of hydropower into an UHV AC-DC network structure, ultra-low frequency oscillations have occurred in the power grid. According to the characteristics of the hydropower unit governor, a small disturbance model of the hydropower unit was established. The impact of various parameters of the hydropower unit governor on the system stability in primary frequency modulation was discussed by using the eigenvalue analysis method, and the power mode and the opening mode were compared. Finally, the impact of the opening mode and the power mode with AGC was studied. The results show that the parameter adjustable range of the opening mode is larger than that of the power mode, but it is more easily affected by AGC. This study lays a foundation for further research on suppression methods of ultra-low frequency oscillations.

In order to realize the reverse power generation operation of large-scale low-lift vertical axial flow pump, using electronic frequency conversion technology instead of mechanical frequency conversion technology, the high voltage four-quadrant frequency converter was applied to Huaiyin second station reverse frequency conversion power generation, and the grid-connected scheme and variable frequency control strategy were analyzed. At the same time, the on-site transformation was carried out to realize the stepless speed regulation of the pump power generation operation. The pump unit can be automatically tracked according to the operating conditions of optimal generating speed to achieve the maximum generating power and maximize the benefit.

A new type of MBC impellerr with a guide vane slot structure was proposed to improve the energy capture and wave reduction efficiency of Savonius-type (S-type) impeller. A multi-objective optimization algorithm combined BP neural network, NSGA-Ⅱ, numerical simulation and experimental test was used to optimize five parameters of the MBC impeller including overlap ratio, gap ratio, internal and external arc angle, internal arc radius, and guide vane size. The performance of the optimal MBC impeller was compared with that of the S-type and MB-type impellers. The results show that the prediction error of the relevant performance values is less than 10% compared to the actual values, verifying the good performance of the established prediction model. The obtained optimal parameters are: overlap ratio of 0.136, gap ratio of 0.003, internal and external arc angle of 5.23°, internal arc radius of 41.42 mm, and guide vane size of 2.83 mm. Compared with the traditional S-type impeller, the optimal MBC impeller has increased energy capture efficiency by 35.8% and wave reduction efficiency by 11%.

Pressure fluctuation in the flow field around a tidal current turbine is one of the key factors affecting the safe and stable operation of the turbine. To evaluate the effects of the duct and the duct-to-rotor clearance ratio δ on the pressure fluctuation characteristics of the tidal current turbine, three-dimensional transient CFD methods and slip-grid techniques were used to perform three-dimensional numerical simulations of the bare turbine and the ducted turbine with the blade tip clearance of δ=0.02D and δ=0.06D, respectively, under the optimal operating conditions (T_TSR=4). By analyzing the unsteady flow phenomenon of the flow field around the turbine, the pressure pulsation and frequency-domain vibration characteristics of the turbine under three different working conditions were obtained. The results show that the pressure fluctuation amplitude of the turbine is basically increasing from the root to the tip of the blade; The addition of a duct can effectively reduce the pressure fluctuation amplitude of the turbine; δ has less impact on the pressure fluctuation coefficient of the turbine and more impact on the vibration characteristics in the frequency domain of the pressure fluctuation; The main frequency of the pressure fluctuation of the turbine is mainly concentrated near the leaf frequency of the corresponding operating conditions. In addition, it is also found that the pressure fluctuation of turbine blade suction surface is stronger than the pressure surface, and the addition of duct can effectively reduce this fluctuation.

The design of culverts in hydraulic engineering involves many common and repetitive tasks. In order to achieve the parametric application of BIM design in culvert engineering, this study has carried out the research on the parametric modelling method of culvert engineering based on Revit platform, and developed a parametric modelling system for culvert through secondary development of Revit according to the relevant technical specifications. By inputting specified parameters, the system can complete the model building, calculation, and drawing, which greatly improves the efficiency of culvert engineering design. The research results achieve a high standard of engineering parametric design, which can provide technical reference for BIM parametric design of similar projects.

Aiming at the problem that the background harmonic voltage fluctuation and the abnormal harmonic measurement samples significantly affect the accuracy of harmonic impedance estimation, a method for calculating utility harmonic impedance based on generalized jackknife least square estimation and data screening is proposed. According to the principle that the assumption of the fluctuation method and least squares regression are the same, the measurement period when the background harmonic voltage fluctuation is stable is selected for the regression calculation, which can restrain the influence of background harmonic voltage fluctuation on impedance estimation. According to the jackknife principle, the harmonic measurement data is resampled, and the generalized least square method is combined to effectively suppress the adverse effects of abnormal measurement data on the regression. The accuracy and practicability of the proposed method are verified by simulation and actual measured data test.

Photovoltaic power generation is affected by the chaotic characteristics of meteorology, and its stochastic, volatile and intermittent characteristics affect the operation of power systems seriously. Aiming at the problem of large dimension of original PV power generation data and the vulnerability of power generation to weather conditions, a data processing method based on Principal Component Analysis (PCA) and BRICH clustering was proposed to reduce the dimensionality of model input variables and facilitate statistical modeling. Secondly, a Copula-Monte Carlo-based probabilistic PV power probabilistic prediction model was constructed to calculate the probabilistic interval prediction of PV power output given the future point prediction values. The model was evaluated based on interval coverage and average width of prediction interval. Finally, the summer data of the actual photovoltaic power station were taken as an example for verification analysis. The results show that the Copula-Monte Carlo method can intuitively show the fluctuation range and expected value of photovoltaic power generation, and is superior to other power prediction models.