Reservoir operation rules, as an important tool to guide reservoir operation, are not only the decision-making reference in the reservoir planning and design period, but also one of the key technologies affecting the comprehensive benefits of the reservoir in the operation and management period. Therefore, based on the historical operation data of reservoirs in the upper reaches of the Yangtze River, the number of periods, early water level, inflow, outflow and current inflow were selected as the influence factors to form the input factor set combined with the reservoir operation principle and operation characteristics. Comprehensively considering the characteristics of operation data and the principle of decision tree, the end of period water level was determined as the model output and then the corresponding simulated water level evaluation index was proposed based on the reservoir regulation capacity. The correlation coefficient and mutual information were used as the correlation evaluation index of model input factors, and the tree Parzen evaluator was introduced to optimize the number of input factors and algorithm super parameters. Finally, the reservoir operation rule extraction model based on decision tree and its integrated model was established and the reservoir operation rule integrating historical operation process and expert experience was formed. The experimental results show that the decision tree and its integrated model have strong ability and applicability in the extraction and application of reservoir operation rules.

The shaft system of hydropower unit has a significant impact on the stability of the unit. The degradation assessment of the shaft system can visually reflect the operating condition of the unit. This paper presents a method for assessing the degradation of the unit’s shaft system using instantaneous orbit feature image and conditional adversarial generative network (CGAN). Firstly, the vertical signals of each bearing were constructed as a complex signal, and the multivariate complex variational mode decomposition (MCVMD) method was used to process the signal and extract the instantaneous orbit features to construct the instantaneous orbit feature images. CGAN was used to construct the health model. The health model can fit the distribution of feature images in different operating conditions in healthy state and thus output health feature images. The healthy indicator was constructed using the differences between real and healthy images. The genetic algorithm was used to optimize the weights of multiple bearings in order to reduce the volatility of the comprehensive degradation curve in the healthy zone. The proposed method was tested on the unit's shaft system data and its validity has been proved.

It was planned to carry out excavation and treatment of the deep trough in Maozhou Estuary for the construction of the new town, which occupied the -3 m deep trough. The Pearl River estuary physical model was used to carry out tide hydrodynamics modeling test and suspended load model test to simulate the siltation distribution of the deep trough after one year of implementation. The test results show that the hydrodynamic characteristics and flow pattern of the study area have changed and the average siltation near the Maozhou Estuary reaching 0.75 m is more serious than that in downstream with 0.53 m, the -3 m deep trough remains connected with the whole widening rate is 1.57% and the thalweg is distributed along the Shenzhen shoreline with the minimum elevation is -3.40 m. The section morphology shows that the siltation on the right side is more serious than the left side and the upstream is more serious than the downstream. The treatment scheme changed the riverbed, the river regime will be significantly adjusted in the short term, but the -3 m deep trough can be maintained. The scheme is generally feasible.

In order to improve the control performance of hydro-turbine speed control system containing surge tanks, this paper proposes a control parameter optimization method based on the improved whale optimization algorithm (IWOA). Firstly, the mathematical model of the turbine speed control system with surge tanks was established. The turbine inlet head-flow transfer function containing the dynamics of surge tanks was established by using the continuity equation and pipe transfer function. And then the turbine speed control system model with surge tanks was formed together with the turbine speed control model. The time integral value of the speed deviation of the turbine in this system was used as the fitness value in the optimization process, and IWOA was used to perform optimization of the PID controller parameters of the study object with the objective of minimizing this fitness. The results show that the IWOA algorithm has the advantages of fast convergence speed and high accuracy, and the optimized PID controller provides better regulation and robustness to various types of disturbances.

The reservoir flood control operation problem has the characteristics of multi-stage, nonlinear and multiple complex constraints. The research of solution method will help to improve the effect of flood control optimal operation. Differential evolution algorithm (DE) has a good effect in the application of reservoir optimal operation, but it is prone to premature convergence and fall into local optimum due to the random search strategy. In order to balance the global and local search ability of DE, this paper proposed an improved differential evolution algorithm SDE, which is used to improve the search ability by considering the differential mutation strategy of fitness ranking and to improve the development ability by random selection mechanism. The related numerical experiments verified that the SDE convergence is significantly better than that of the DE, GA, PSO, and ACOR. The results of case study show that the SDE is better than POA and DE in terms of the feasible solution, calculation time, accuracy, convergence stability and speed. The average flood-peak rate of the SDE is 0.17%-4.26% higher than the POA, and is 0.13%-1.26% higher than the DE.

The power imbalance between DC side and AC side of single-phase grid-connected photovoltaic inverter leads to double frequency power pulsation on DC side. The additional active power decoupling circuit can effectively suppress the secondary ripple, but due to the additional components, the system efficiency of single-phase inverter will be reduced. Aiming at the above problems, this paper proposes a control strategy based on Buck converter that can reduce the power loss of decoupling circuit. By calculating the power loss of the decoupling circuit and analyzing the working constraints, the relationship between the power loss and the average voltage of the decoupling capacitor was obtained, and then a control strategy to directly control the average voltage of the decoupling capacitor was proposed. Simulation results show that the proposed control strategy can effectively suppress the DC side voltage ripple and reduce the power loss of the decoupled circuit.

A similar basin identification method was proposed to improve the reliability of similar basin identification for hydrological forecasting in ungauged basin. The method introduced the basin time-varying feature information and constructed a time-varying feature matrix (TVFM). A dimension reduction method for the TVFM was proposed to obtain the basin feature vector. The classical K-means clustering method was adopted to implement the identification of the similar basins. Seventeen natural catchments in Jiangxi Province were selected and the Xin'anjiang model was applied in this research. A series of studies were carried out which includes feature vector and feature matrix construction, similar basin identification, parameter transfer, and comparison & analysis of hydrological forecasting results. The following conclusions can be drawn. The proposed TVFM can achieve better forecasting results in ungauged basins. Compared with the traditional similar basin identification method based on time-invariant underlying surface information, the prediction accuracy is improved. The similar basin identification based on time-varying comprehensive features generates the best predictions, and the prediction accuracy based on time-varying meteorological features is better than that based only on time-invariant underlying surface features. Comparison with the single factor methods, the directional problem of the parameter transfer can be partially solved by the proposed comprehensive method. Unfortunately, the directional problem cannot be completely overcame until recently.

In view of the problem that the comprehensive output coefficient of power station deviates from the actual situation in varying degrees with the accumulation of operation time, the change of operating conditions, unit wear, the comprehensive output coefficient was calibrated according to the average comprehensive output coefficient and the piecewise fitting coefficient. The piecewise fitting method was further divided into piecewise fitting according to the water head and piecewise fitting considering the water head and power generation flow in terms of the dispatching characteristics. The results were verified by precision evaluation. Combined with the historical operation process of Hongjiadu Hydropower Station, a case study was carried out. The results show that compared with the actual results, the relative error of the average coefficient method is 2.64%, that of the piecewise fitting method according to the head is 2.52%, and that of the piecewise fitting method considering the head and flow is 0.59%. The piecewise fitting method is closer to the actual production process than the average comprehensive output coefficient method, and the piecewise fitting method considering the head and power flow is the most accurate.

The geometric characteristics of landslide are closely related to the rainfall infiltration process, which is the key internal factor to control the stability of rainfall-induced landslides. There are many rainfall-induced landslides in the Three Gorges Reservoir area, and it is of great significance to deeply reveal the body shape characteristics of rainfall-induced landslides (landslide whose stability is sensitive to rainfall in hydraulic engineering are generally referred to as rainfall-induced landslides) for the identification and prevention of landslide disasters in the reservoir area. In this paper, the data of 275 rainfall-type sedimentary landslides in the Three Gorges Reservoir area were collected, and their body shape characteristics were statistically analyzed. The rainfall-type landslides in the area are narrow and long, thin in thickness and gentle in slope. Combined with the numerical simulation of the rainfall infiltration process of typical landslides, it is found that the landslides of this type have a larger rain-receiving area and infiltrated rainwater is more likely to infiltrate the sliding bed, which makes the effect of rainfall more significant, and is not conducive to the stability of the slope under rainfall conditions.

Baishuihe landslide is a typical representative of bedding landslide in the Three Gorges reservoir area. However, the research on its formation evolution process and deformation characteristics after water storage is not deep. On the basis of field geological investigation and the latest survey data and GPS monitoring data, this paper makes a detailed study on the rock and soil structure of Baishuihe landslide and its deformation characteristics after impounding. The results show that the evolution process of Baishuihe landslide has gone through the early stage of landslide, the rock landslide and the accumulation landslide. At present, Baishuihe landslide is in the accumulation landslide stage; Baishuihe accumulation landslide is the product of vertical superposition of landslide accumulation bodies caused by the destruction of the second-stage rock landslide, and there is a clay layer in the middle. Corresponding to the water level of 135 m and 156-175 m, the deformation of Baishuihe landslide can be divided into two stages. The deformation characteristics of Baishuihe landslide are gently inclined steps and steeply inclined steps. The research results provide the corresponding decision-making suggestions for the treatment of Baishui River landslide, and also provide the direction for the later treatment of geological disasters with similar structural characteristics.