Applied Mechanics and Materials Vols. 212-213

Abstract: This paper develops a hybrid differential evolution based multi-objective approach for the optimal economic emission dispatch (EED) of the hydrothermal power system (HPS), considering non-smooth fuel cost and emission level functions. The hybrid differential evolution (HDE) equipped with an accelerated operation and a migration operation can efficiently search and actively explore solutions. The multiplier updating (MU) is introduced to handle the equality and inequality constraints of the HPS, and the ε-constraint technique is employed to manage the multi-objective problem. To show the advantages of the proposed algorithm, one example addressing the best compromise is applied to test the EED problem of the HPS. The proposed approach integrates the HDE, the MU and the ε-constraint technique, revealing that the proposed approach has the following merits - ease of implementation; applicability to non-smooth fuel cost and emission level functions; better effectiveness than the previous method; better efficiency than differential evolution (DE) with the MU (DE-MU), and the requirement for only a small population in applying the optimal EED problem of the HPS.

Abstract: Probability distribution is adopted to evaluate the cost risk of large hydropower project. Risk factors are firstly identified through Work Breakdown Structure(WBS), Cost Breakdown Structure(CBS) and Risk Breakdown Structure(RBS), and then individual risk factor probability distribution is measured by method combined Monte Carlo simulation model and the controlled interval memory (CIM) model. By superimposing individual ones, probability distribution of cost under the influence of a number of risk factors is achieved, which provides effective information for investment decision and cost control.

Abstract: The topography is low and flat in the estuarine region of the Yangtze River, where waterlog and salt-affected soil is all through a latent threat to the agricultural development for long time. After the Three-Gorge Project is built up, the Three-Gorge Reservoir adjusts seasonably runoff will impact on the dynamic of soil water and salt in the region. These influence relations are very complicated. In spring, it will make the river water level up that discharge increases, so it will be not in favor of desalting. At the same time, mineralization degree of groundwater will decrease, in favor of desalting. In autumn-winter, it will make the river water level down that the discharge decreases, in favor of desalting. But, the mineralization degree of groundwater will increase, simultaneously salty tide invasion will strengthen, so not in favor of desalting. The elementary predicted result of numerical simulation shows that salification will be bigger in autumn than desalinization in spring. The impact degree of the project on the regime of soil salt will be gradually weakened along the river up from the estuary, the nearer to the sea, the bigger the impact, and from cross profiles, the nearer to the river, the bigger the impact. Especially within the range of 4 kilometers off the river, it is more possible that soil will produce salification or secondary salinization.

Abstract: The RFPM(Radial Flux Permanent Magnet) generator has numerous advantages such as high output voltage and output power, high efficiency, manufacture easy but the slotted RFPM generator configuration produces the cogging torque. The cogging torque would be the source of acoustic noise and vibration. This paper presents the electromagnetic structure design analysis and the cogging torque reduction design of RFPM generator. It is composed of the inner stator and the outer stator and internal rotor. We called it as DG-RFPMG(Dual Generator-Radial Flux Permanent Magnet Generator). Firstly, the design of the pole-arc ratio of rotor magnets to reduce cogging torque is studied. Secondly, the design of the stator displacement of the outer stator and the inner stator to reduce the cogging torque is studied. Finally, the combined design optimization considering both the pole- arc ratio and the stator displacement to reduce the cogging torque is studied. The design of DG-RFPMG was calculated by 2D FEM(Finite Element Method).

Abstract: It is imperative to strengthen the high-risk work system assessment and accidents prevention and control of hydropower construction hazards based on the identification of risk factors. Work system safety is a function of many factors, besides it is dynamic and complex. There may be relations and dependencies among the safety factors. Therefore, work system safety should be analyzed in a holistic manner. In this study, the accidents data analysis is used to identify the links among the factors, which are used as factor dominance relation in Analytic Network Process. Therefore, the influence factors of engineering construction safety are worthy of studying. Through extensive reading literature and information, making contrast and analyzing, researching and other methods, finishing the preliminary indicators of construction safety influencing factors, after conducting questionnaire survey, ultimately identified 19 indicators of factors and based on these indicators draw SEM model by AMOS software. With the influencing factors, it gives assessment result through the variable assignment and the factors weight derived from SEM and ANP method.

Abstract: This paper, starting from the professional point of view of turbine governor and according to various data in the test, presents a preliminary analysis of results in combination of various tests competed after Xiaowan Power Station 700MW hydropower unit speed governor was put into island mode operation after the Chu Hui direct current line was off-stream (trial). Meanwhile, it describes the adjustment that the speed control system should make once the power system is in the island mode, including the conversion of the control mode, the switch of control parameter and optimization of control algorithm, focuses on analyzing the optimization of control strategy of the speed governor in the island mode, and discusses the active and speed adjustment method of the units and the associated performance indicators.

Abstract: In this paper, nonlinear turbine model and hydraulic system which is one penstock one machine dynamic differential equation with elastic water column are combined. Hamiltonian function of hydraulic turbine is constructed. By applying Hamiltonian orthogonal decomposition realization and dissipation realization method, generalized Hamiltonian model of hydraulic turbine is built. Connected with generator third-order Hamiltonian model of single machine infinite bus system, generalized Hamiltonian model of hydraulic generator unit is established. This paper provides certain theory basis for research operation and control dynamics mechanism of hydraulic generator unit in generalized Hamiltonian system framework.

Abstract: Normally, it is much complicated and difficult to design flood discharge and energy dissipation with large discharge. In this paper, twelve designed schemes of a curtain hydropower station were compared and analyzed repeatedly. It provides better reference scheme for engineering design. On weir surface and middle orifice local hydraulic model with geometry scale of 1:60, the writer tested and researched on energy dissipation capacity ,velocity and flow pattern, pressure distribution and related hydraulics problems of the curtain hydropower station discharging structure layout. Basically practicable discharging structure pattern and stilling pool pattern were put forward, through comparison and optimization of more than ten schemes. The study result showed that the surface orifice adapting proper pattern of flaring gate pier was favorable to increase the energy dissipation efficiency and shorten the length of stilling pool, but had no effect on the phenomenon of water wing hitting both sides of guide wall caused by flaring gate pier, the schemes of canceling flaring gate pier of surface orifice and adapting the declined pattern stilling pool could decrease the stilling pool floor plate velocity of under flow energy dissipation efficiently ,at the same time diminish the phenomenon of water wing hitting guide wall on both sides caused by flaring gate pier and obtain certain satisfying energy dissipation effect, moreover it had much heuristic and inspirational effect on similar projects.

Abstract: The 3# bulb turbine in Hongjiang Hydropower Plant has faced the problem of output deficiency since its commission in Sept. 2003, which caused a large economic loss. Following simple theoretical analyses on the main factors affecting the turbine’s output and efficiency, the field test schemes were determined to measure the shapes and intervals of guide vanes and runner blades of the 3#, 5# and 6# turbines. The test results discover that the average blade intervals of the 3# turbine are generally less than those of the 5# one. Suggestions on runner blade installation adjustment and combined curve modification are given.

Abstract: Applying the reciprocal accumulated generating and the constructing background value of non-equidistant sequence of GRM(1,1) model based on fitting the first accumulated generating sequence with non-homogeneous exponential law for the problem of lower precision as well as lower adaptability in non-equidistant GM(1,1) model, the calculation formulas were deduced and a non-equidistant GRM(1,1) model generated by reciprocal accumulated was put forward. The grey GRM(1,1) model can be used in non-equidistant interval & equidistant interval time series and has the characteristic of high precision as well as high adaptability. Example validates the practicability and reliability of the proposed model.