The accurate positioning of target is an important link in robot technology. Based on machine learning algorithm, this study firstly analyzed the location positioning principle of binocular vision of ...robot, then extracted features of the target using speeded-up robust features (SURF) method, positioned the location using Back Propagation Neural Networks (BPNN) method, and tested the method through experiments. The experimental results showed that the feature extraction of SURF method was fast, about 0.2 s, and was less affected by noise. It was found from the positioning results that the output position of the BPNN method was basically consistent with the actual position, and errors in X, Y and Z directions were very small, which could meet the positioning needs of the robot. The experimental results verify the effectiveness of machine learning method and provide some theoretical support for its further promotion and application in practice.
Traditionally, the optimal power flow (OPF) problem is solved in a centralized manner. However, with continuous expansion of the scale of multi-area interconnected power systems, realistic ...applications of the centralized method face additional challenges. In this paper, we propose a fully decentralized OPF algorithm for multi-area interconnected power systems based on the distributed interior point method, where solving the regional correction equation was converted into solving a parametric quadratic programming problem during each Newton-Raphson iteration. This is a novel approach to tackle the decentralized OPF problems. We analyzed the convergence property of this algorithm. The proposed approach is fully decentralized without central coordinator and parameter tuning, and is robust to network partitioning. Furthermore, this decentralized algorithm enjoys the same convergence performance and accuracy as the centralized interior point method. Results on a 3-bus test system, 4 IEEE test systems, and a real 4-area 6056-bus interconnected system show the benefits of the proposed method.
A high-voltage direct current system using modular multilevel converter (MMC-HVDC) is a potential candidate for grid integration of renewable energy over long distances. The dc-link fault is an issue ...MMC-HVDC must deal with, especially for the nonpermanent faults when using overhead lines. This paper proposed a protection scheme to implement fast fault clearance and automatic recovery for nonpermanent faults on dc lines. By employing double thyristor switches, the freewheeling effect of diodes is eliminated and the dc-link fault current is allowed to freely decay to zero. Then, the dc arc can be naturally extinguished and the insulation on the short-circuit point can be restored. The thyristor switches convert the dc-link fault into an ac short circuit of the ac grid through MMC arms. The ac short-circuit current can be cleared simply by turning off all thyristor switches. Since circuit breakers are not tripped during fault clearance, MMC can immediately and automatically rebuild the dc-link voltage and restart power transmission. Simulation results using PSCAD/EMTDC have verified the validity of the proposed protection scheme.
Modular multilevel converters (MMC) are considered a top converter alternative for voltage-source converter (VSC) high-voltage, direct current (HVDC) applications. Main circuit design and converter ...performance evaluation are always important issues to consider before installing a VSC-HVDC system. Investigation into a steady-state analysis method for an MMC-based VSC-HVDC system is necessary. This paper finds a circular interaction among the electrical quantities in an MMC. Through this circular interaction, a key equation can be established to solve the unknown circulating current. A new steady-state model is developed to simply and accurately describe the explicit analytical expressions for various voltage and current quantities in an MMC. The accuracy of the expressions is improved by the consideration of the circulating current when deriving all the analytical expressions. The model's simplicity is demonstrated by having only one key equation to solve. Based on the analytical expressions for the arm voltages, the equivalent circuits for MMC are proposed to improve the current understanding of the operation of MMC. The feasibility and accuracy of the proposed method are verified by comparing its results with the simulation and experimental results.
The research on the adsorption equilibria, kinetics, and increase in process temperature of the volatile organic compound (VOC) adsorption in porous materials ensures safe production, thereby ...reducing production costs and improving separation efficiency. Therefore, it is critical in predicting the entire adsorption process based on minimal or no experimental input of the adsorbate and adsorbent. We discuss, in this review, the factors that affect the adsorption performance of VOCs in activated carbons, including the adsorption equilibrium, adsorption kinetics, and exotherm during adsorption. Subsequently, the existing prediction models are summarized and compared concerning the adsorption equilibrium, adsorption kinetics, and exothermic process of adsorption. We then propose a new prediction model based on intermolecular interaction and provide an outlook toward the design and manipulation of efficient adsorbents for the VOC system.
The behavior of surface water, especially the adsorption and dissociation characteristics, is a key to understanding and promoting photocatalytic and biomedical applications of titanium dioxide ...materials. Using molecular dynamics simulations with the ReaxFF force field, we study the interactions between water and five different TiO2 surfaces that are of interest to both experiments and theoretical calculations. The results show that TiO2 surfaces demonstrate different reactivities for water dissociation rutile (011) > TiO2–B (100) > anatase (001) > rutile (110), and there is no water dissociation observed on the TiO2–B (001) surface. The simulations also reveal that the water dissociation and the TiO2 surface chemistry change, and the new surface Ti–OH and O–H functional groups affect the orientation of other near-surface water molecules. On the reactive surface, such as the rutile (110) surface, water dissociated and formed new Ti–OH and O–H bonds on the surface. Those functional groups enhanced the hydrogen bond networking with the near-surface water molecules and their configurations. On the nonreactive TiO2–B (001) surface where no molecular or dissociative water adsorption is observed, near-surface water can also form hydrogen bonds with surface oxygen atoms of TiO2, but their distance to the surface is longer than that on the rutile (011) surface.
Abstract Under the current scouring, submarine cables are prone to be exposed, suspended, and even vortex‐induced vibration (VIV), threatening their mechanical and electrical properties. In this ...contribution, a finite element simulation model of 110‐kV single‐core optical fibre composite submarine cable is established. The natural frequency and resonant frequency of the model are obtained through wet mode analysis and harmonic response analysis. Then the VIV is simulated by the fluid–structure coupling method. Moreover, the stress extraction method of the torsional optical fibre position under the VIV is proposed. The results show that when the reduced speed is 2.57, the submarine cable appears beating vibration, which is composed of two vibrations with similar frequencies. When the reduced speed is 7.08, the vibration frequency is about 7.813 Hz, causing a rapid increase in vibration amplitude. The stress distribution of the torsional optical fibre presents a mirror image relationship at two moments separated by half a vibration cycle. Also, the frequency of stress change is the same as the frequency of VIV, which can judge whether the VIV occurs. The VIV range and position can be determined by the location where the stress changes the most.
Freezing fraction and collision coefficient are the key parameters in the ice accretion model, which should be calculated to predict the icing trend for transmission lines. Here a mathematical ...relation between freezing fraction and collision coefficient was derived using the simplified head balance model of transmission lines icing. Combined with the empirical formula of the liquid water content in air, a calculation method of the freezing fraction and collision coefficient was proposed using the ice surface temperature of transmission lines and the icing mass growth rate. The method to measure the icing mass growth rate based on online monitoring data and icing experiments was proposed. The icing experiments were carried out in the low‐temperature ice chamber with the same parameters as the online monitoring environmental parameters. The values of the freezing fraction and collision coefficient were calculated by using the online monitoring data and icing experiments data respectively, the calculation results were compared. The maximum relative differences between the calculation results from the online monitoring data and the icing experiments data do not exceed 18%, which proves the validity of the calculation method of the freezing fraction and collision coefficient in ice accretion model of transmission lines.
To reduce the risk imposed by use of defected composite insulators on the operation of power grids, this paper introduces a nondestructive ultrasonic phased array (UPA) technique that allows ...effectively test such insulators. The method offers a great potential by reducing inspection time as well as allowing for analyzing components characterized by a complex geometry. The UPA inspection system utilizes an open-ended rectangular waveguide sensor, operating at frequency of 2.5 MHz. The system is simple, safe and relatively inexpensive. In this work, samples of silicone rubber composite insulators with various types of detects are studied and the obtained results show that void defects in the bulk of the insulator housing are easiest to be detected. Holes under insulator sheds can also be detected by the edge of scanning range. For the defects near the core-shed interface, the detection becomes possible by comparisons with sample without defects.
For in-service transmission lines, insulator icing condition depends on analysis of images collected by cameras installed on towers, and ice type analysis is mostly completed by human beings, which ...is infeasible to monitor a large area. Although image processing is successfully applied to segmentation of insulators from aerial images, there are few literatures on automatically determining ice types on insulators via image processing. In this paper, a recognition method of ice types on in-service glass insulators is established based on a texture feature description operator. Uniform Local Binary Patterns (ULBP) and Improved Uniform Local Binary Patterns (IULBP) were adopted for texture feature extraction of typical images of six ice types including glaze ice, heavy rime, medium rime, light rime, partial rime and snow. The six ice types are concluded based on icing insulator images and corresponding meteorological data from China Southern Power Grid Transmission Line (Icing) Online Monitoring System. Ice types are recognized by correlation coefficient calculation of texture histograms. The experiment results show that IULBP obtains better results for recognition of the six ice types as each ice type has distinguished texture features.
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