Journal of Hydroelectric Engineering

水力发电学报

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2020 Vol. 39, No. 12 Published: 2020-12-25

	1	Dynamic management of hydropower construction resources based on positioning system ^Hot!
		FAN Qixiang, LIU Yuanda, Li Guo, XIE Liang, WANG Yi, FAN Kai, WANG Liutao, NING Zeyu
		DOI: 10.11660/slfdxb.20201201
		Managing construction resources of large-scale projects such as labor and equipment has always been the core of engineering management, and its dynamic and precise requirements can be met through modern information and communication technologies that provide a strong technical guarantee. Facing the management challenges of high resource mobility, multiple cross-operations, and complex professional technique, we have developed a comprehensive technology system of construction positioning–including personnel positioning and device positioning–that is applicable to different operations demanding different positioning accuracies and response speeds, in combination with the construction of hydropower projects in the lower Jinsha River. Applying this system and related data technologies, we can collect the real-time data of personnel and device positioning, analyze comprehensively construction behaviors and real-time feedback, and manage dynamically resource investment, moving track, operating status, etc. Thus, a real-time refined management of construction resources is achieved for large-scale hydropower projects, improving the safety and quality management of engineering construction.
		2020 Vol. 39 (12): 1-15 [Abstract] ( 116 ) PDF (5937 KB) ( 457 )

	16	Base functions for generating slip surfaces of slopes
		JIE Yuxin, XIE Qi, ZHOU Ting
		DOI: 10.11660/slfdxb.20201202
		The degrees of freedom of the slip surfaces of slopes, when generated using elementary functions, are reduced greatly and the surface smoothness can be guaranteed. Based on the existing theories, this paper presents a new general method for constructing slip surfaces using different base functions and achieving a unified framework for the generation. We transform the geometric problems involved in slip surface generation to determining the parameters of base functions in algebra, and recommend how to solve the constraint condition of the coefficients. Five base functions are suggested and are used in a classical example for slope stability analysis. Safety factors and instability acceleration are calculated using Morgenstern-Price method. Results show the base functions recommended by the authors meet the requirements and can even generate some special slip surfaces that cannot be achieved by traditional methods.
		2020 Vol. 39 (12): 16-24 [Abstract] ( 107 ) PDF (470 KB) ( 369 )

	25	Study on driving factors of temporal and spatial evolution of water level in Poyang Lake
		GUO Zhentian, HUANG Feng, GUO Lidan, WU Yao
		DOI: 10.11660/slfdxb.20201203
		In recent years, water level in Poyang Lake has changed significantly, threatening the ecological security of wetlands. First, this paper uses the Mann-Kendall method to analyze water level changes in this lake in the period of 1990 to 2016.Then, we construct a BP neural network model for simulation of the lake water level, and quantify through scenario analysis the temporal and spatial characteristics of the contribution made to the lake level change by the flow changes in the Yangtze mainstream, lake inflows from the Poyang’s sub-basins, and the topographic change. In time evolution, flow variations in the Yangtze mainstream is the main driving factor of the decreases in the average monthly water level at all the hydrological stations from July through September, and topography is the main driving factor of the decreases in the Poyang’s water level in dry season. Spatially, in the period of July to November, the pull down effects of the Yangtze mainstream flow on the monthly average water levels at different stations rank in a decreasing order as Xingzi station, Duchang station, Tangyin station, and Kangshan station; the pull down effects of topography rank as Duchang station, Xingzi station, Tangyin station, and Kangshan station. Changes in topography are the major cause of the maximum water level variations that occur at the Duchang station.
		2020 Vol. 39 (12): 25-36 [Abstract] ( 166 ) PDF (3789 KB) ( 393 )

	37	Study on compensation benefit calculations and distribution mechanism of cascade hydropower stations
		ZHANG Lechen, LI Wenbin, HE Yong, ZHANG Taiheng, YANG Ming
		DOI: 10.11660/slfdxb.20201204
		Aimed at difficulties in quantifying and distributing the compensation benefit of cascade hydropower stations, this paper presents a new solution to obtain compensation benefits of any hydropower station in the basin, and establishes a benefit distribution mechanism based on the improved technique for order preference by similarity to an ideal solution (TOPSIS), using traditional distribution methods as indicators. This solution is applied to the calculations and distribution of compensation benefits for ten cascade hydropower stations on the Wujiang River mainstream. The results show our solution is featured with a solid theoretical basis and simple calculations and can clarify the compensation relationship among the five giving power stations and the downstream power stations. This improved TOPSIS method gives a weight of each evaluation index that meets our expectation, and its distribution calculations are reasonable, thereby providing a theoretical basis for the interest games among the hydropower stations and helping promote cascade cooperation and maximize the hydropower generation benefits of the basin.
		2020 Vol. 39 (12): 37-46 [Abstract] ( 169 ) PDF (455 KB) ( 313 )

	47	Comparison of consistency measures of hydrological series based on statistical experiments
		NIU Jingyi, XIE Ping, WU Linqian, SANGYanfang, WU Ziyi, HUO Jingqun
		DOI: 10.11660/slfdxb.20201205
		Many methods are available to identify different components of a hydrologic time series, but differences in their performances are not understood clearly. Based on the probability theory, this paper describes two types of error evaluation standards for comparison of the consistency test accuracies assessed by five measures–Hurst measure, Bartels measure, Runs measure, Ljung-Box Q (LBQ) measure, and Spearman measure. Analysis results of the synthetic series, generated by the Monte-Carlo method, show the performances of all these measures are mainly affected by different variation types and different variation degrees, depending little on the mean, variation coefficient, or skewness coefficient of the stochastic components. Comparatively, Bartels measure, Runs measure and LBQ measure perform best, followed by Spearman measure, while Hurst measure performs worst. Application to five observed hydrologic time series indicate all the five measures have certain errors due to significant variability in the series but can achieve accurate assessments of the consistent parts of the series. Thus, we suggest that for higher accuracy, the two components of a time series, variation part and consistent part, be identified separately, with the variation part to be identified first and then the rest to be calculated for consistency test.
		2020 Vol. 39 (12): 47-61 [Abstract] ( 155 ) PDF (534 KB) ( 304 )

	62	Long-term optimal dispatching of cascade hydropower stations under large-scale wind power grid integration
		ZHAO Zhenyu, ZHANG Yi, LI Gang, LI Xiufeng, JIANG Yang, ZHOU Binbin, CHENG Chuntian
		DOI: 10.11660/slfdxb.20201206
		With new energies developing rapidly, power grids need more regulation capacity under the condition of large-scale wind power grid integration; more cascade hydropower stations start joint operation with large-scale wind power, putting their flexible regulation capacity into use. This paper examines the influence of wind power’s reverse-peak shaving on the generation of such stations, and obtains the upper and lower bounds of their daily generation. Then, we construct a bridge between long-term and short-term dispatching by using these bounds and constraints, considering the short-term shaving characteristics in long-term optimal dispatching. The method is tested in a case study of the cascade hydropower stations in the downstream of Lancang River and the wind power nearby in southwest China. The results show these stations’ long-term dispatching modes need to be adjusted after joint operation with wind power, especially their water storage decisions for the periods before and after flood season, verifying our new approach for large-scale wind power grid integration.
		2020 Vol. 39 (12): 62-75 [Abstract] ( 170 ) PDF (880 KB) ( 425 )

	76	Study on non-stationary frequency calculations for the annual runoff of Yellow River mainstream
		LU Fan, XIAO Weihua, DAI Yanyu, SONG Xinyi
		DOI: 10.11660/slfdxb.20201207
		This paper presents an application of a generalized additive model for location, scale and shape (GAMLSS) with time-varying statistical parameters to calculations of the non-stationary hydrological frequencies of annual runoff series of the Yellow River mainstream. First, we discuss the evaluation methods of model structure, parameter estimation, and fitting effect. Then, we construct a set of alternative models for non-stationary hydrological frequency calculation, based on analysis of runoff change trends of the annual series of six hydrological stations at the Yellow mainstream for the period of 1956 to 2017, and select the optimal model as featured with the probability distribution type and parameter setting that has the minimum AIC value. This model and its fitting effect are tested against the statistical characteristics of the residual series and the quantile plot of design runoffs. From the test, the optimized model manifests good fitting to the runoff series, and the design runoffs corresponding to the runoff series of each station decrease with time. Thus, we suggest that the future evaluation, allocation or operation of water resources fully consider the non-stationary effect of runoffs and carry out predictions and uncertainty assessment of water resources in changing environments.
		2020 Vol. 39 (12): 76-84 [Abstract] ( 164 ) PDF (2435 KB) ( 550 )

	85	Experimental study on occurrence and processes of neck cutoff in meandering rivers under variable discharges
		WU Xinyu, LI Zhiwei, HU Xuyue
		DOI: 10.11660/slfdxb.20201208
		Neck cutoff is a sudden change phenomenon occurring in the morphological evolution of meandering rivers, but its processes and mechanisms have not yet formed a unified consensus. To reproduce its occurrence and processes, the method of testing a natural model in a laboratory flume is used in this work to study its behaviors under constant and variable flow conditions–the channel evolution before and after cutting off, the formation of the new cutoff channel, and the cutoff threshold. Experimental results show that whether the river discharge varies or not, the main factor that causes the cut off is bank scour upstream and downstream of the neck. The well-developed model meandering rivers in the flume are regularly featured with a sinuosity range of 6-7, a width ratio (neck width to river channel width) of about 0.43, and a channel bed of non-sticky sand. Under the conditions of flow rates per unit width of 0.0039-0.0069 m2/s and a longitudinal riverbed slope of 1‰, neck cutoff can be triggered after long time scour on the river bank. Just before cutting off, the local sinuosity of successive river bay is increased, and the planar channel shape rotates downstream; after cutting off, the new cutoff channel experiences three stages of time evolution–longitudinal scour, horizontal broadening, and relatively slow development.
		2020 Vol. 39 (12): 85-93 [Abstract] ( 102 ) PDF (1979 KB) ( 250 )

	94	Study on comprehensive benefit assessment systems for low impact development practices
		YU Qian, LI Na, WANG Shan, MENG Yuting
		DOI: 10.11660/slfdxb.20201209
		Low impact development (LID) practice, a resilient solution, could effectively solve new and old water problems in urban areas; its comprehensive benefits are more significant compared to the single function of grey infrastructures oriented at controlling rainfall runoff volumes. To evaluate the benefits at the planning and design stage, this paper constructs a comprehensive assessment system of five different LID measures, including 18 indicators for disaster reduction benefits, economic benefits, environmental benefits, and social benefits. Application of this new system to the Jinan Daminghu sponge city construction pilot area indicates that under the 24h design storms with 5-year, 10-year and 20-year return periods, the LID measures reduce direct flood loss by 13.86%, 4.28% and 4.09% respectively, and increase groundwater recharge volume by 2.23, 2.86 and 2.87 million m3 respectively. And with green roofs constructed by LID, the air contents of NO2, O3, SO2 and PM10 could be reduced by 0.38-0.61, 0.74-1.17, 0.29-0.52 and 0.14-0.17 t/yr. In addition, LID practices help enhance environmental aesthetics.
		2020 Vol. 39 (12): 94-103 [Abstract] ( 179 ) PDF (1036 KB) ( 271 )

	104	Fault diagnosis of hydroelectric sets based on SVD and DBN
		LI Hui, FAN Zhichao, LI Hua, BAI Liang, JIA Rong, LUO Xingqi
		DOI: 10.11660/slfdxb.20201210
		In order to solve the problem of low signal-to-noise ratio of the early faults of hydroelectric sets, Singular Value Decomposition (SVD) and Deep Belief Network (DBN) are combined for fault diagnosis in this study. First, a Hankel matrix was constructed by using a vibration signal containing noise to decompose its singular values; and effective singular values, selected through the singular value difference spectrum method, were used to reconstruct a phase space and achieve noise reduction. Then, singular value decomposition was applied to the signals denoised, and the resulted singular value sequence was used to construct a feature vector. Finally, a DBN classifier model was developed to realize the fault diagnosis of hydroelectric sets and compared with BP neural network and multi-class support vector machine. The results show this method can identify the fault type of hydroelectric sets more reliably and efficiently.
		2020 Vol. 39 (12): 104-112 [Abstract] ( 143 ) PDF (1526 KB) ( 337 )

	113	Investigation on formations and alleviation of inter-blade vortices in Francis turbine
		WANG Zhaoning, SUN Longgang, GUO Pengcheng, WANG Xiuling
		DOI: 10.11660/slfdxb.20201211
		Hydropower units are forced to operate in part load conditions more frequently to balance the power grid parameters due to tremendous development of renewable energy resources; as a consequence, the characteristics of inter-blade vortices under such conditions become a significant index for evaluating hydraulic design and optimization of hydraulic turbines. This paper analyzes systematically the formation mechanism of inter-blade vortices in a Francis turbine through theoretical analysis and scale model experiment, and examines new effective measures for alleviating the incipient vortices and their development. Results show that breaking the pressure gradient that would otherwise be continuous and steady, due to the runner tending to adapt to the wide range of flow rate changes, could be one of the factors affecting the vortex formation. We find that design modification of the runner blades–shortening the runner flow passage, adopting a design of bionic streamline, or controlling the twist degree of the blades–can effectively suppress the incipient vortices and reduce their developing rate, achieving a useful result for expanding the stable operation range of Francis turbines.
		2020 Vol. 39 (12): 113-120 [Abstract] ( 145 ) PDF (1113 KB) ( 406 )