Algorithm Recognizing Nonlinear-Load-Current States and Having Dynamic Iteration Step Size

2018 ◽  
Author(s):  
Zicheng Li ◽  
Gongjian Zhao ◽  
Guohai Liu ◽  
Zhaoling Chen ◽  
Dezhi Xu ◽  
...  
Keyword(s):  
Iteration Step ◽  
Step Size ◽  
Nonlinear Load ◽  
Load Current ◽  
Dynamic Iteration

Numerical Investigation of Sub-Iteration Criterions for Unsteady Flow Computations with Dual-Time Method

2013 ◽  
Vol 432 ◽  
pp. 189-195
Author(s):  
Guang Ning Li ◽  
Min Xu
Keyword(s):  
Unsteady Flow ◽  
Unsteady Flows ◽  
Numerical Results ◽  
Iteration Step ◽  
Convergence Criterion ◽  
Step Size ◽  
Time Step ◽  
Time Step Size ◽  
Physical Time ◽  
New Criterion

The convergence of sub-iteration with the dual-time method is very important for the prediction of unsteady flow field. The influence of sub-iteration step number, criterion of sub-iteration convergence and the choice of physical time step size on the calculation results are discussed by solving of the two-dimensional unsteady Euler equations. A new convergence criterion (named residual criterion) of sub-iteration for unsteady flows is proposed, and the unsteady flow test case AGARD-CT5 is calculated to verify the new criterion. The results show that, with the same criterion of sub-iteration, the results from different physical time step sizes are in agreement with each other. The difference between the experiment data and the numerical results are small, and if the sub-iteration criterion used is reasonable and small enough, the dependence of numerical results of unsteady flows on the physical time step will be decreased as possible. The new criterion of sub-iteration for dual-time step unsteady calculations can be used for engineering problem.

scholarly journals A Maximum Power Point Tracking Algorithm of Load Current Maximization-Perturbation and Observation Method with Variable Step Size

Symmetry ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 244
Author(s):  
Lieping Zhang ◽  
Zhengzhong Wang ◽  
Peng Cao ◽  
Shenglan Zhang
Keyword(s):  
Photovoltaic Cell ◽  
Maximum Power ◽  
Variable Step Size ◽  
Step Size ◽  
Maximum Power Point ◽  
Load Current ◽  
Point Tracking ◽  
Power Point Tracking ◽  
Variable Step ◽  
Power Point

A photovoltaic power supply with a simple structure and high tracking efficiency is needed in self-powered, wireless sensor networks. First, a maximum power point tracking (MPPT) algorithm, including the load current maximization-perturbation and observation (LCM-P&O) methods, with a fixed step size, is proposed by integrating the traditional load current maximization (LCM) method and perturbation and observation (P&O) method. By sampling the changes of load current and photovoltaic cell input current once the disturbance is applied, the pulse width modulation (PWM) regulation mode, i.e., increasing or reducing, can be determined in the next process. Then, the above algorithm is improved by using the variable step size strategy. By comparing the difference between the absolute value of the observed current value and the theoretical current value at the maximum power point of the photovoltaic cell with the set threshold value, the variable step size for perturbation is determined. MATLAB simulation results show that the LCM-P&O method, with a variable step size, has faster convergence speed and higher tracking accuracy. Finally, the two MPPT algorithms are tested and analyzed under constant voltage source input and indoor fluorescent lamp illumination through an actual circuit, respectively. The experimental results show that the LCM-P&O method with variable step size has a higher tracking efficiency, about 90%–92%, and has higher stability and lower power consumption.

Power Quality Improvement by Solar Photo-voltaic / Wind Energy Integrated System Using Unified Power Quality Conditioner

2017 ◽  
Vol 8 (3) ◽  
pp. 1416 ◽  
Author(s):  
Sarita Samal ◽  
Prakash Kumar Hota
Keyword(s):  
Wind Energy ◽  
Power Quality ◽  
Reactive Power ◽  
Integrated System ◽  
Quality Analysis ◽  
Nonlinear Load ◽  
Load Current ◽  
Voltage Unbalance ◽  
Photo Voltaic ◽  
Sudden Decrease

The  real problems in diminution of power quality occurs due to the rapid growth of nonlinear load are leads to sudden decrease of source voltage for a few seconds  i.e sag, swell, harmonics in source and load current, voltage unbalance etc. All these   problems can be compensated by using Unified Power Quality Controller (UPQC) and the operation of UPQC depends upon the available voltage across capacitor present in dc link. If the capacitor voltage is maintained constant then it gives satisfactory performance. The proposed research is basically on designing of Photo Voltaic (PV) /Wind energy fed to the dc link capacitor of UPQC so as to maintain proper voltage across it and operate the UPQC for power quality analysis. The said model is simulated in Matlab and results are verified by using FFT analysis.The proposed PV/ Wind energy-UPQC is design in Matlab simulation for reduction of voltage sag, swell, interruption of voltage, harmonics in load current and compensation of active and reactive power.

scholarly journals Nonparametric Tensor Completion Based on Gradient Descent and Nonconvex Penalty

Symmetry ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1512
Author(s):  
Kai Xu ◽  
Zhi Xiong
Keyword(s):  
Gradient Descent ◽  
Image Inpainting ◽  
Descent Method ◽  
Singular Value ◽  
Low Rank ◽  
Iteration Step ◽  
Gradient Descent Method ◽  
Tensor Completion ◽  
Step Size ◽  
Nonconvex Penalty

Existing tensor completion methods all require some hyperparameters. However, these hyperparameters determine the performance of each method, and it is difficult to tune them. In this paper, we propose a novel nonparametric tensor completion method, which formulates tensor completion as an unconstrained optimization problem and designs an efficient iterative method to solve it. In each iteration, we not only calculate the missing entries by the aid of data correlation, but consider the low-rank of tensor and the convergence speed of iteration. Our iteration is based on the gradient descent method, and approximates the gradient descent direction with tensor matricization and singular value decomposition. Considering the symmetry of every dimension of a tensor, the optimal unfolding direction in each iteration may be different. So we select the optimal unfolding direction by scaled latent nuclear norm in each iteration. Moreover, we design formula for the iteration step-size based on the nonconvex penalty. During the iterative process, we store the tensor in sparsity and adopt the power method to compute the maximum singular value quickly. The experiments of image inpainting and link prediction show that our method is competitive with six state-of-the-art methods.

scholarly journals Influence of the iteration step size to finding solutions

2018 ◽  
Vol 251 ◽  
pp. 03031
Author(s):  
Aleksey Klochko ◽  
Asmik Klochko
Keyword(s):  
Reliability Index ◽  
Distribution Network ◽  
Distribution Networks ◽  
Gas Pipeline ◽  
Iteration Step ◽  
Network Configuration ◽  
Gas Distribution ◽  
Reliable Operation ◽  
Step Size ◽  
Gas Supply

The article considers the issues of obtaining a network configuration by the criterion of maximizing the reliability index. The rationally designed configuration of the gas distribution network for the selected gas supply scheme ensures reliable operation throughout the life of gas pipeline. The results are recommended in designing of gas distribution networks, as well as when determining the reserve for improving the reliability of the network for the adopted gas supply scheme for subscribers.

scholarly journals Quality Control for Medium Voltage Insulator via a Knowledge-Informed SPSA Based on Historical Gradient Approximations

Processes ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 146 ◽  
Author(s):  
Xiangsong Kong ◽  
Jiaming Guo ◽  
Dongbin Zheng ◽  
Ji Zhang ◽  
Wei Fu
Keyword(s):  
Quality Control ◽  
Process Parameters ◽  
Weight Control ◽  
Control Method ◽  
Parameters Optimization ◽  
Experimental Simulation ◽  
Iteration Step ◽  
Step Size ◽  
Medium Voltage ◽  
Voltage Insulator

Medium voltage insulators are essential and versatile components in electrical engineering. Quality control of the manufacturing process for the insulators has a significant role in their economic production and reliable operation. As the quality of medium voltage insulator is mainly affected by the process parameters of the automatic pressure gelation process (APG), the optimal process settings are required to achieve a satisfactory quality target. However, traditional process parameters’ optimization methods are often cumbersome and cost-consuming. Moreover, the operational cost of APG for insulator production is relatively high. Therefore, the determination of the optimal settings becomes a significant challenge for the quality control of insulators. To address the above issues, an idea of knowledge-informed optimization was proposed in this study. Based on the above idea, a knowledge-informed simultaneous perturbation stochastic approximation (SPSA) methodology was formulated to reduce the optimization costs, and thus improve the efficiency of quality control. Considering the characteristics of SPSA, the historical gradient approximations generated during the optimization process were utilized to improve the accuracy of gradient estimations and to tune the iteration step size adaptively. Therefore, an implementation of a quality control strategy of knowledge-informed SPSA based on historical gradient approximations (GK-SPSA) was thus constructed. In this paper, the GK-SPSA-based quality control method was applied to the weight control of a kind of post insulators. The experimental simulation results showed that the revised knowledge-informed SPSA was effective and efficient on quality control of medium voltage insulators.

Localization from Connectivity in Wireless Sensor Networks Based on Distributed Weight-Multidimensional Scaling

2012 ◽  
Vol 220-223 ◽  
pp. 1887-1891
Author(s):  
Zhong Sheng Li ◽  
Zhi Long Shan
Keyword(s):  
Multidimensional Scaling ◽  
Wireless Sensor ◽  
Iteration Step ◽  
Localization Algorithm ◽  
Stable Convergence ◽  
Step Size ◽  
Localization Accuracy ◽  
Simulation Results ◽  
Absolute Coordinates ◽  
Function Connectivity

A localization algorithm from connectivity based on distributed weighted-multidimensional scaling (cdwMDS) algorithm is proposed in this paper. Each sensor selects a neighbor sensor adaptively, calculates the iteration step size with the average connectivity and updates the estimate location by optimizing the local cost function. Connectivity is used to determine the step size of gradient iterative optimization in this algorithm. After getting the estimated positions, a relative map is built and the absolute coordinates can be obtained. Simulation results show that this method could achieve higher localization accuracy and more stable convergence.

A Novel Variable Step-Size LMS Harmonic Detecting Algorithm

2011 ◽  
Vol 464 ◽  
pp. 179-182
Author(s):  
Jian Ning Yang ◽  
Jia Jun Guan ◽  
Yan Min Ning ◽  
Chuan Gu
Keyword(s):  
Time Window ◽  
Tracking Error ◽  
Lms Algorithm ◽  
Variable Step Size ◽  
Least Mean Square ◽  
Matlab Simulation ◽  
Step Size ◽  
Load Current ◽  
Grid Load ◽  
Improved Algorithm

This paper proposed a novel adaptive algorithm applied to the harmonic detection that improves the power quality and suppressing grid harmonic. Considering the signal noise ratio (SNR) of the load current is low, the improved algorithm uses the coherent average estimation of the proportion of error signal in the total signal instead of system error to update the step-size, so the step-size only depends on the real system tracking error, and the steady state error is small when the system is close to stable. In addition, the algorithm adopts the time window action of mean estimation to control the influence of past signal on the present one, which produces a big step-size when the system changes. Compared with the fixed step-size least mean square (LMS) algorithm in a grid load current detected by matlab simulation, the improved algorithm has a faster convergence rate, a higher stability precision, and a better performance of anti-noise, the simulation shows the effectiveness of the method.

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