Recent Advances in Electrical & Electronic Engineering - Volume 13, Issue 8, 2020

Background: The hop-based positioning method is a straightforward, low-cost, and feasible positioning method. Methods: Most previous hop-based algorithms assume that the network is isotropic and uniformly distributed, which often does not reflect real-world conditions. In practice, the network may be anisotropic, which makes the hop count between nodes may not match the real distance well. Results: As a result of this issue for hop-based positioning methods, in this paper, we propose a novel scheme that builds a skeleton model between anchor nodes to represent the anisotropy of a network. During the process of building the skeleton model, we use the corrected Akaike's Information Criterion (AICc), which can assist in the construction of a reliable and high accuracy skeleton model. With the help of the skeleton model with AICc, an unknown node can get a more accurate and reliable estimated position. Conclusion: The results of both theoretical analysis and experimental simulation show that the optimal hop-distance conversion model can be achieved, and compared to other similar algorithms, the proposed algorithm can obtain the position estimation result in a fast and accurate manner.

Background: In Computed Tomography (CT), it is often not possible for the subject to remain stationary during a scan. Unfortunately, a patient motion would result in degraded spatial resolution and image artifacts. It is desirable to improve reconstruction quality and reduce motion artifacts caused by patient motion. Methods: In this work, a method was proposed to eliminate the influence of the motion on image quality, based on the phase correlation method. Based on our previous work, projections were first taken by Radon transform and motion parameters were estimated by the phase-only correlation of projections in the Radon domain. In addition, an improved image reconstruction algorithm was performed to compensate for the motion effects. Results: Experimental results proved that the proposed method could not only obtain high precision and good real-time performance but also ensure a superior artifact reduction. Conclusion: Besides, the efficacy of the proposed method has been demonstrated in both simulated and human head experiments.

Background: A multi-motor synchronous drive control system is widely used in many fields, such as electric vehicle drive, paper making, and printing. Methods: On the basis of the optimized structure of ADRC, a fuzzy first-order active disturbance rejection controller was developed. Double channels compensation of extended state observer was employed to estimate and compensate the total disturbances, and an approximate linearization and deterministic system was obtained. As the parameters of ADRC are adjusted online by a fuzzy controller, the performance of the controller is effectively improved. Results: Based on the SIMATIC S7-300 induction motor control experimental platform, the performances of anti-interference and tracking performance are tested. Conclusion: The actual experimental results indicated that compared with PID control, induction motor drive system controlled by fuzzy ADRC has higher dynamic and static status and following performances and stronger anti-interference abilities.

Background: A compact complex impedance-transforming balun for UHF frequencies, which is based on a coupled-line structure that matched all ports and provided high output port isolation, was designed in this paper. Methods: A lumped component transformation was used to minimize circuit size. The implemented circuit operated at 433 MHz with the reflection coefficients less than -16 dB at all ports, 0.22 dB amplitude balance and 180° phase balance at the output ports. The signal coupling between the output ports was -16.8 dB. The circuit size is small at 0.032λ. Results: Complex impedance-transforming baluns were designed to operate at 433 MHz. The source impedance at port 1 was set at Zs = 12 - j12Ω and the load impedances at port 2 and 3 were set at ZL = 80 + j30Ω. Conclusion: A compact complex impedance-transforming balun at UHF frequency, with all ports matched and high isolations, was designed and illustrated in this paper.

Background: Unmanned Surface Vehicles (USV) can undertake risks or special tasks in marine independently and will be widely used in the future. In the autonomous navigation of USV equipped with vision camera, the water boundary line needs to be detected in real time and it is one of these key intelligent environment perception methods for USV. Methods: An efficient water boundary line detection method based on Gray Level Co-occurrence Matrix (GLCM) texture entropy is proposed. In image preprocessing, the high-brightness areas are eliminated to avoid the effects of water boundary line detection. Results: GLCM entropy is employed to segment water, land and air for water line regression. The proposed method is efficient for the images with high-brightness areas. Conclusion: The experimental results demonstrate that the proposed method is not only more accurate than the existing water boundary line detection method, but also has good real-time performance and is suitable for the application in USV.

Background: To preserve sharp edges and image details while removing noise, this paper presents a denoising method based on Support Vector Machine (SVM) ensemble for detecting noise. Methods: The proposed method ISVM can be divided into two stages: noise detection and noise recovery. In the first stage, local binary features and weighted difference features are extracted as input features vector of ISVM, and multiple sub-SVM classifiers are integrated to form the noise classification model of ISVM by iteratively updating the sample weight. The pixels are divided into noise points and signal points. In the noise recovery stage, according to the classification results of the previous stage, only the gray value of the noise point is replaced, and the replacement value is the weighted mean value with the reciprocal of the quadratic square of the distance as the weight. Results: Finally, the replacement value at the noise point and the original pixel value of the signal point are reconstructed to get the denoised image. Conclusion: The experiments demonstrate that ISVM can achieve a noise detection rate of up to 99.68%. ISVM is highly effective in the denoising task, produces a visually pleasing denoised image with clear edge information, and offers remarkable improvement compared to that of the BPDF and DAMF.

Background: It is important to improve the quality of service by using congestion detection technology to find the potential congestion as early as possible in wireless sensor network. Methods: So an improved congestion control scheme based on traffic assignment and reassignment algorithm is proposed for congestion avoidance, detection and mitigation. The congestion area of the network is detected by predicting and setting threshold. When the congestion occurs, sensor nodes can be recovery quickly from congestion by adopting reasonable method of traffic reassignment. And the method can ensure the data in the congestion areas can be transferred to noncongestion areas as soon as possible. Results: The simulation results indicate that the proposed scheme can reduce the number of loss packets, improve the throughput, stabilize the average transmission rate of source node and reduce the end-to-end delay. Conclusion: So the proposed scheme can enhance the overall performance of the network. Keywords: wireless sensor network; congestion control; congestion detection; congestion mitigation; traffic assignment; traffic reassignment.

Background: Traditional thyristor-based three-phase soft starters of induction motor often suffer from high starting current and heavy harmonics. Moreover, both the trigger pulse generation and driving circuit design are usually complicated. Methods: To address these issues, we propose a novel soft starter structure using fully controlled IGBTs in this paper. Compared to approaches of traditional design, this structure only uses twophase as the input, and each phase is controlled by a power module that is composed of one IGBT and four diodes. Results: Consequently, both driving circuit and control design are greatly simplified due to the requirement of fewer controlled power semiconductor switches, which leads to the reduction of the total cost. Conclusion: Both Matlab/Simulink simulation results and experimental results on a prototype demonstrate that the proposed soft starter can achieve better performances than traditional thyristorbased soft starters for Starting Current (RMS) and harmonics.

Background: China's power resources are unevenly distributed in geography, and the supply-demand imbalance becomes worse due to regional economic disparities. It is essential to optimize the allocation of power resources through cross-provincial and cross-regional power trading. Methods: This paper uses load forecasting, transaction subject data declaration, and route optimization models to achieve optimal allocation of electricity and power resources cross-provincial and cross-regional and maximize social benefits. Gray theory is used to predict the medium and longterm loads, while multi-agent technology is used to report the power trading price. Results: Cross-provincial and cross-regional power trading become a network flow problem, through which we can find the optimized complete trading paths. Conclusion: Numerical case study results have verified the efficiency of the proposed method in optimizing power allocation across provinces and regions.

Background: Distributed Sustainable Energy Generation (DSEG) has become a leading trend in modern R&D to achieve practical, financial, and environmental benefits. With respect to the power system, the benefits are minimization of power failures, enhancement of energy quality & reliability, congestion relief, and smart/micro grid demand response. The widespread use of modern technologies encourages the use of DSEG for safe power production and power loss reduction. Besides, it also poses new challenges such as optimal placement of relays, protection device settings, and voltage control problems in power systems. Among various solutions reported in the literature, a widely accepted solution seems to be the deployment of Fault Current Limiter (FCL) to minimize DSEG impacts. However, FCLs are an expensive option to restore relay coordination. The adaptive protection scheme provides benefits to the smart grid's advanced features and serves as an efficient solution to address new DSEG and FCL challenges. Objectives: This paper presents an extensive review of the effect of DSEG on distribution systems from the safety point of view, different optimization techniques used for adaptive protections, optimal relay coordination, and merits & demerits of FCL. Methods: The paper discusses various recent optimization and hybrid optimization techniques used for solving the Optimal Relay Coordination model (ORC). Adaptive and FCL based non-adaptive techniques are also discussed to solve this model. An attempt has also been made to present a comparative study of various optimization techniques in tabular form, considering different bus models and their outcomes. Results: Various optimization techniques have been used by the researchers to solve significant issues of DSEG impacts on the distribution grid. Conclusion: Comparative study of these techniques shows that Water cycle optimization, hybrid whale-GWO and GSA-SQP algorithms give better results in solving the ORC problem. FCL based non-adaptive technique was found better as compared with adaptive techniques because a greater number of DGs can be integrated on a grid with less complexity.

Background: The power industry has been evolving continuously and influenced by a competitive deregulated market. The crucial demand to maximize the efficiency of the existing equipment requires it’s proper management. Flexible AC Transmission System (FACTS) are flexible devices, which provide dynamic control over the power system to cope with its dynamic nature. Methods: An extensive review is carried out on FACT devices covering its classification, importance, optimal placement and influence on the power systems. Results: In this paper, different techniques to identify the optimal location of placing FACT devices have been discussed and compared, as the placement of these devices in the power system is of utmost importance for its efficiency. Conclusion: This paper summarizes techniques available for optimal placement of FACTS devices in order to improve power system performance. It will serve as a ready reference for the future researchers in this field and help them in selecting the proper devices to carry out their work.

Background: The output voltage frequency for the previously proposed "phase hopping" AC-AC frequency conversion technology is determined by the law that the number of output voltage cycles is reduced by one relative to the power frequency in a large cycle containing six jumps. According to the law, only a limited number of output frequencies, such as 37.5 Hz, 42.86 Hz and 45 Hz are found. Due to the large spacing between the output frequencies, the "phase hopping" frequency conversion technology is difficult to put into practical use. Methods: In this paper, the law of the output frequency control is generalized so that the number of output cycles in a large cycle is reduced by n relative to the power frequency. The analysis shows that the appropriate selection of large cycles, including the number of power frequency cycles and the value of n, can find more frequencies to be used. Reducing the interval between the output frequencies within 1Hz. Results: The analysis results were verified in simulation by MATLAB, and the harmonics and the feasibility of the actual application were analyzed. Conclusion: Finally, an experimental platform was built and an experimental analysis was carried out. The experimental results show that the theoretical and simulation analyses are correct.

Background: The vehicle pose detection plays an important role in monitoring vehicle behavior and the parking situation. The real-time detection of vehicle pose with high accuracy is of great importance. Objective: The goal of the work is to construct a new network to detect the vehicle angle based on the regression Convolutional Neural Network (CNN). The main contribution is that several traditional regression CNNs are combined as the Multi-Collaborative Regression CNN (MCR-CNN), which greatly enhances the vehicle angle detection precision and eliminates the abnormal detection error. Methods: Two challenges with respect to the traditional regression CNN have been revealed in detecting the vehicle pose angle. The first challenge is the detection failure resulting from the conversion of the periodic angle to the linear angle, while the second is the big detection error if the training sample value is very small. An MCR-CNN is proposed to solve the first challenge. And a 2- stage method is proposed to solve the second challenge. The architecture of the MCR-CNN is designed in detail. After the training and testing data sets are constructed, the MCR-CNN is trained and tested for vehicle angle detection. Results: The experimental results show that the testing samples with the error below 4° account for 95% of the total testing samples based on the proposed MCR-CNN. The MCR-CNN has significant advantages over the traditional vehicle pose detection method. Conclusion: The proposed MCR-CNN cannot only detect the vehicle angle in real-time, but also has a very high detection accuracy and robustness. The proposed approach can be used for autonomous vehicles and monitoring of the parking lot.

Background: The Demand Side Management (DSM) technology is playing an increasingly important role in the power system, in order to promote the real-time supply and demand balance of the power grid and improve the economy and safety of the power grid. Objective: To realize the flexible and continuous reactive power control of demand side load, a reactive power control strategy for the demand side back-to-back converter (DS-B2BC) is proposed. Methods: First, DS-B2BC is proposed. Then, the reactive power control model of DS-B2BC and its control loop are designed, and the reactive power control model, based on the Virtual Synchronous Motor (VSM), is established. Results: The simulation results verify that the reactive power control strategy proposed in this paper is effective, which can control the demand side load reactive power flexibly and continuously. Conclusion: Moreover, the strategy can counteract the disturbance from the power grid simultaneously.

Background: In this paper, an assessment of active power filter (APF) performance is presented under direct and indirect current control schemes through on-line compensation theory. Methods: Conventional Direct Current Control (DCC) measures both load current and filter current beside source and DC-link voltages, while Indirect Current Control (ICC) measures only source current beside voltage measurements. Both DCC and ICC control algorithms are implemented using 80C196KC low-cost microcontroller. Results: The performance parameters of APF are compared under two methods, and it is assigned that ICC gives a better performance with lower cost due to reduced number of sensors. The DC-link output voltage is controlled through simple PI-controller, and the PWM switching signals required by APF power circuit is obtained by hysteresis current controller. Conclusion: The comparative simulation and experimental results exhibit that performance of APF due to ICC scheme is superior than DCC one.

Background: Compared with the traditional series mechanism, the parallel mechanism has a better kinematic performance. Structural size error is the main factor affecting the accuracy of parallel mechanisms. Objective: The paper mainly studies the compensation of the rod length error, the moving platform radius error and the fixed platform radius error of 3-UPU parallel mechanism. Methods: To establish a generalized forward and inverse solution equation with error compensation, the position change of the moving platform is measured by a laser interferometer, and the change amount of the three connecting rod lengths at the corresponding position is recorded. Optimized by least squares method, the optimized error compensation values are compensated to the kinematics algorithm of the numerical control system, and the positioning accuracy is improved. Results: The results show that the positioning accuracy is higher when the mechanism moves in the lower plane, and the positioning error in the z axis direction is smaller than x, y, y=x, y=-x axis. Conclusion: After the error compensation, the overall positioning accuracy of the mechanism is increased by 60%.