Recent Advances in Electrical & Electronic Engineering - Volume 14, Issue 7, 2021

Background: The two main stages are utilized for feature extraction, from which the first stage consists of a penalty weight to the neighbor graph’s edges. The edge penalty weights are minimized by the neighbor sub-graph extraction to produce the set of feature patterns. For noisy data, the second stage is helpful. Methodology: In order to realize the measurement of the geometric dimensions of the ship block, this paper uses the theory of computer vision and reverse engineering to obtain the data of the segmented- hull with the method of digitizing the physical parts based on the vision, and processes the data by using the relevant knowledge of reverse engineering. Results: The results show that the efficiency of the edge extraction algorithm based on mathematical morphology is 30% higher than that of the mesh generation method. An adaptive corner detection algorithm based on the edge can adaptively determine the size of the support area and accurately detect the corner position. Conclusion: According to the characteristics of the point cloud of ship hull segment data, an adaptive corner detection algorithm based on the edge is adopted to verify its feasibility.

Background: The effect of teaching and training in physical sports is improved by the sports demonstration system. The two-dimensional sports demonstration system is widely applied for the training of athletes. In accurate motion positioning, there exists a certain visual deficiency and the two-dimensional sports demonstration system is analyzed by kinematics. Methodology: Aiming at the problems in the real-time tracking of fast-moving targets in sports images, an automatic tracking method of sports images based on the registration of landmark points of the passive optical motion capture system is proposed. Moreover, it aims to build a human model and divide the human model into several limb segments; find the corresponding relationship between the first frame of motion data and template data to complete the first frame of motion data registration; based on the smallest non-rigid deformation and point set matching error, find the corresponding relationship between the current frame of motion data and the previous frame of registered motion data; through the mark points, follow up to complete the registration process of the marker. Results: Experiments show that the average processing accuracy of this algorithm can reach over 85% and the processing time of a single frame of motion data is t<1/60s, which can meet real-time requirements. Conclusion: The multi-point set least-squares matching algorithm is used to rigidly correct the registered landmark data. No manual intervention is required for the entire mark registration process.

Background: The character motion of 3D animation production is difficult, and to solve this problem, motion-pose capture technology is very effective. The workload of character motion control is reduced by this technique and the animation development is improved. It is used in virtual training grounds and real-time tracking of the motion. The complete contour features cannot be efficiently acquired by the 3D visual motion technique. The 3D visual motion amplitude tracking method in sports is studied in order to improve the training quality of athletes effectively. However, when the current method is used for motion amplitude tracking, the markers in the adjacent monocular sequence motion amplitude images cannot be calculated. Methodology: At this point, there is a problem of a large tracking error of 3D visual motion amplitude. To this end, a 3D amplitude tracking method in sports based on inverse kinematics is proposed. This method locates the marker points that appear in the adjacent monocular sequence motion range and merges it with the rotation angle method to predict the position of the motion range in the image. Results: The motion amplitude is obtained, and 3D visual motion amplitude is outside the optimization area; this has been used as a basis to complete the tracking of the 3D visual motion amplitude in sports. Conclusion: Experimental simulation performed in MATLAB proves the high tracking accuracy of the proposed method.

Background: The paper aimed at studying a large number of classified and sensitive information transmission security issues brought by 5G mobile communication system. Methods: In this paper, the principle of beamforming and its shortcomings are introduced by combining the large-scale MIMO technology and directional modulation technology, and the directional modulation technology based on antenna subset selection and the hybrid array is introduced to realize the safe transmission target. The results show that large-scale MIMO technology has become a key technology of 5G mobile communication, but the factors such as multipath fading in the actual wireless channel have not been fully considered, and the accurate estimation error of channel state information (CSI) will affect the ideal security level it can achieve. Results: The combined application of massive MIMO technology and directional modulation technology in the 5G system brings security to its communication. Conclusion: Directional modulation technology based on signal modulation has become an important research point of the 5G system because it does not need to consider the eavesdropper's computing power and can achieve the purpose of safe transmission by disturbing the signal constellation in the unexpected direction.

Background: A deep understanding of digital media art is required to promote the development of animation design. Methods: The functions and application effects of animation design were analyzed in detail to improve its quality. In this study, we used Maya embedded language (MEL) to simulate and analyze the walking, running, and jumping effects of animated characters. Results: The results showed that the use of digital media animation control technology based on MEL to realize animation character movement effect could improve production efficiency and character motion authenticity by 30% and 40%, respectively, and reduce work intensity by 50%. We used MEL to resolve the production problems of three-dimensional (3D) animation. Conclusion: Applying the law of motion to characters makes their movement highly realistic. The production of 3D animation is simple, efficient, recyclable, and highly operable.

Two VSC-MTDC control strategies with different combinations of controllers are proposed to eliminate transient fluctuations in the DC voltage stability, resulting from a power imbalance in a VSC-MTDC connected to wind farms. First, an analysis is performed of a topological model of a VSC converter station and a VSC-MTDC, as well as of a mathematical model of a wind turbine. Then, the principles and characteristics of DC voltage slope control, constant active power control, and inner loop current control used in the VSC-MTDC are introduced. Finally, the PSCAD/EMTDC platform is used to establish an electromagnetic transient model of a wind farm connected to a parallel three-terminal VSC-HVDC. An analysis is performed for three cases of single- phase grounding faults on the rectifier and inverter sides of a converter station and of the withdrawal of the converter station on the rectifier side. Next, the fault response characteristics of VSCMTDC are compared and analyzed. The simulation results verify the effectiveness of the two control strategies, both of which enable the system to maintain DC voltage stability and active power balance in the event of a fault. Background: The use of a VSC-MTDC to connect wind power to the grid has attracted considerable attention in recent years. A suitable VSC-MTDC control method can enable the stable operation of a power grid. Objective: The study aims to eliminate transient fluctuations in the DC voltage stability resulting from a power imbalance in a VSC-MTDC connected to a wind farm. Methods: First, the topological structure and a model of a three-terminal VSC-HVDC system connected to wind farms are studied. Second, an analysis is performed of the outer loop DC voltage slope control, constant active power control and inner loop current control of the converter station of a VSC-MTDC. Two different control strategies are proposed for the parallel three-terminal VSCHVDC system: the first is DC voltage slope control for the rectifier station and constant active power control for the inverter station, and the second is DC voltage slope control for the inverter station and constant active power for the rectifier station. Finally, a parallel three-terminal VSC-HVDC model is built based on the PSCAD/EMTDC platform and used to verify the accuracy and effectiveness of the proposed control strategy. Results: The results of simulation analysis of the faults on the rectifier and inverter sides of the system show that both strategies can restore the system to the stable operation. The effectiveness of the proposed control strategy is thus verified. Conclusion: The control strategy proposed in this paper provides a technical reference for designing a VSC-MTDC system for wind farms.

Background: Fast and reliable fault detection methods are the main technical challenges faced by photovoltaic grid-connected systems through Modular Multilevel Converters (MMC) during the development. Objective: Existing fault detection methods have many problems, such as the inability of non-linear elements to form accurate analytical expressions, the difficulty of setting protection thresholds, and the long detection time. Methods: Aiming at the problems above, this paper proposes a rapid fault detection method for photovoltaic grid-connected systems based on Recurrent Neural Network (RNN). Results: The phase-to-mode transformation is used to extract the fault feature quantity to get the RNN input data. The hidden layer unit of the RNN is trained through a large amount of simulation data, and the opening instruction is given to the DC circuit breaker. Conclusion: The simulation verification results show that the proposed fault detection method has the advantage of faster detection speed without difficulties in setting and complicated calculation.

Background: Modern upgrades of power grids and a rapidly expanding economy complexify the uncertainties of electricity demand. Objective: The objective of the study is to have a more precise prediction on the demand side, which is beneficial in affirming the stable operation of the power system. Methods: This paper presents a combined electricity forecasting method based on the users clustering and stacking ensemble learning to mine underlying properties of different individual consumers. The preprocessed electricity consumption profiles are inputted into the DBSCAN clustering algorithm to obtain the clusters. The alternative models are tailored for different clusters in the stacking fusion framework for training and testing. Results: Experimental results on the operating data of Shandong Power Grid show that the proposed method has higher prediction accuracy and better generalization ability. Conclusion: The framework is of great significance for improving the level of power supply service.