A nonintrusive fast residential load identification algorithm based on frequency‐domain template filtering

User‐side load monitoring is a key technology to realize smart utilization of electric power. Since the traditional intrusive load monitoring involves a comparatively large economic cost and execution complexity, this paper studies a way to rapidly identify residential power load in a nonintrusive monitoring mode. A template‐filtering‐based nonintrusive, rapid residential load identification algorithm is proposed, which is based on frequency‐domain analysis of current signals, in combination with the current model when the nonintrusive monitoring load is in operation, and by making use of the fact that the spectrum components of the current signals working independently are completely contained in the hybrid current spectrum. Characteristic currents of the various loads in the power grid are acquired a priori to establish the characteristic filter, and 0–1 valuation is performed on their spectrum components to get the template filter. The template filter is then used to filter the hybrid current signals captured in the nonintrusive mode, and the operation status of the loads is judged and determined after quantification of the filtered frequency components. For the same type of load under different operating conditions, the template filter can be commonly used. Efficiency of the algorithm is verified by making use of the actually collected power consumption data, which is able to accurately identify the load operation status. Furthermore, the algorithm is shown to be highly efficient and can be realized via fast Fourier transform (FFT), and its hardware packaging can be easily realized. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Frequency domain subspace identification with the aid of the w‐operator

Frequency domain subspace identification algorithms have been studied recently by several researchers in the literature, motivated by the significant development of the more popular time domain counterparts. Usually, this class of methods are focused on discrete‐time models, since in the case of continuous‐time models, the data matrices often become ill‐conditioned if we simply rewrite the Laplace operator s as s = jω, where ω denotes the frequency. This paper proposes an efficient and convenient approach to frequency domain subspace identification for continuous‐time systems. The operator w = (s−α)/(s+α) is introduced to avoid the ill‐conditioned problem. Hence, the system can be identified based on a state‐space model in the w‐operator. Then the estimated w‐operator state‐space model can be transformed back to the common continuous‐time state‐space model. An instrumental variable matrix in the frequency domain is also proposed to obtain consistent estimates of the equivalent system matrices in the presence of measurement noise. Simulation results are included to verify the efficiency of the proposed algorithms. © 2000 Scripta Technica, Electr Eng Jpn, 132(1): 46–56, 2000     

Adaptive threshold generation in robust fault detection using interval models: time‐domain and frequency‐domain approaches

In this paper, robust fault detection is addressed on the basis of evaluating the residual energy that it is compared against worst‐case value (threshold) generated considering parametric modeling uncertainty using interval models. The evaluation of the residual/threshold energy can be performed either in the time or frequency domain. This paper proposes methods to compute such energy in the two domains. The first method generates the adaptive threshold in the time domain through determining the worst‐case time evolution of the residual energy using a zonotope‐based algorithm. The second method evaluates the worst‐case energy evolution in the frequency domain using the Kharitonov polynomials. Results obtained using both approaches are related through the Parseval's theorem. Finally, two application examples (a smart servoactuator and a two DOFs helicopter) will be used to assess the validity of the proposed approaches and compare the results obtained. Copyright © 2012 John Wiley & Sons, Ltd.     

Accuracy of the frequency‐domain TLM method and its application to microwave circuits

This paper investigates the accuracy and convergence of frequency‐domain (FD) TLM solutions and describes a method to identify non‐physical solutions. The numerical dispersion characteristics of various discretization schemes (‘nodes’) are compared. The occurrence of non‐physical solutions when solving three‐dimensional problems is discussed and a method to identify the non‐physical solutions is described. The accuracy of the FDTLM method is shown to be of second order as long as singularities are absent, whereas it is between first and second order if the computational domain includes field singularities. Copyright © 2002 John Wiley & Sons, Ltd.     

Modeling of doubly lossy and dispersive media with the time‐domain finite‐element dual‐field domain‐decomposition algorithm

A numerical scheme is presented for the time‐domain finite‐element modeling of an electrically and magnetically lossy and dispersive medium in the dual‐field domain‐decomposition method. Existing approaches for modeling doubly lossy and dispersive media are extended to the dual‐field case, yielding a general dual‐field domain‐decomposition scheme for modeling large‐scale electromagnetic problems involving such media. A quantitative analysis is performed to estimate the error induced by the modeling of medium dispersion. Copyright © 2012 John Wiley & Sons, Ltd.     

Optimization of genetic algorithm for reconstruction of cross‐phase modulation frequency‐resolved optical gating data

We implemented a frequency‐resolved optical gating (FROG) measurement method using cross‐phase modulation in a highly birefringent microstructure optical fiber. The standard FROG data reconstruction algorithm of generalized projection failed for this setup and we successfully used the genetic algorithm (GA) instead which is less prone to get stuck to local minima. GA has several parameters that must be set up to suitable values. We describe the experimental setup and the algorithm and present our findings on what GA parameters are crucial and what are their optimal values. A single run of the algorithm takes 7 min on contemporary CPUs, making the algorithm suitable for routine laboratory work. Copyright © 2010 John Wiley & Sons, Ltd.     

A convex optimization approach to adaptive stabilization of discrete‐time LTI systems with polytopic uncertainties

This paper suggests a simple convex optimization approach to state‐feedback adaptive stabilization problem for a class of discrete‐time LTI systems subject to polytopic uncertainties. The proposed method relies on estimating the uncertain parameters by solving an online optimization at each time step, such as a linear or quadratic programming, and then, on tuning the control law with that information, which can be conceptually viewed as a kind of gain‐scheduling or indirect adaptive control. Specifically, an admissible domain of stabilizing state‐feedback gain matrices is designed offline by means of linear matrix inequality problems, and based on the online estimation of the uncertain parameters, the state‐feedback gain matrix is calculated over the set of stabilizing feedback gains. The proposed stabilization algorithm guarantees the asymptotic stability of the overall closed‐loop control system. An example is given to show the effectiveness of the proposed approach. Copyright © 2014 John Wiley & Sons, Ltd.     

Sparse leaky‐LMS algorithm for system identification and its convergence analysis

In this paper, a novel adaptive filter for sparse systems is proposed. The proposed algorithm incorporates a log‐sum penalty into the cost function of the standard leaky least mean square (LMS) algorithm, which results in a shrinkage in the update equation. This shrinkage, in turn, enhances the performance of the adaptive filter, especially, when the majority of unknown system coefficients are zero. Convergence analysis of the proposed algorithm is presented, and a stability criterion for the algorithm is derived. This algorithm is given a name of zero‐attracting leaky‐LMS (ZA‐LLMS) algorithm. The performance of the proposed ZA‐LLMS algorithm is compared to those of the standard leaky‐LMS and ZA‐LMS algorithms in sparse system identification settings, and it shows superior performance compared to the aforementioned algorithms. Copyright © 2013 John Wiley & Sons, Ltd.     

A new false‐root identification method based on two‐terminal fault location algorithm for double‐circuit transmission lines

A fault location algorithm without synchronization for double‐circuit transmission lines does not require sampling synchronization, reduces the cost, and has a higher engineering value, but the algorithm still needs to be improved in the false‐root identification. This paper conducts further studies on this issue. First, the false‐root problem of the fault location algorithm without synchronization is analyzed, and then a new false‐root identification method is proposed, which is based on the difference of the existence of the false root in the calculation of the voltage amplitude along the line with different electrical moduli. It can solve the problem of the traditional method, which cannot distinguish between voltage amplitudes when they are close. Second, considering the shortcoming of the existing phase‐mode transformation matrix, a new phase‐mode transformation matrix applied to double‐circuit lines is deduced, which is based on the six‐sequence component method; it can be combined with the new false‐root identification method, thereby realizing false‐root identification under various types of faults. Finally, fault location is realized by using the moduli in the mold domain. The principle does not need to synchronize data in two terminals and is not affected by the fault types, fault resistances, and other factors. As is shown in a large number of Alternative Transients Program version of Electro‐Magnetic Transients Program (ATP‐EMTP) simulation results, the fault location has a higher accuracy © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A useful identification method to build low‐order transfer function models based on frequency response for small‐signal stability analysis

This paper presents a scheme of small‐signal stability analysis for very large radial power systems. Generally, a radial power system can be easily classified as one main system and some external systems. Therefore, if accurate low‐order model of the external systems could be identified, the analysis effort for small‐signal stability can be reduced. Some dynamic reduction methods are proposed. Especially, the frequency‐domain least‐squares approximation methods, which are powerful and have high numerical reliability. This paper proposes a modal rebuild logic to improve the result obtained by the frequency‐domain least‐squares approximation methods. The proposed method provides high accuracy and a practical low‐order transfer function model. This paper introduces the usefulness of the proposed method with some numerical examples. In addition, merging sophisticated data handling and advanced applications in order to reduce human efforts is also discussed. This paper mentions the importance of automated node ID handling in order to realize the classification of system data into some partial data sets. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A two‐step scheme for polynomial NARX model identification based on MOEA with prescreening process

Polynomial NARX (nonlinear autoregressive with exogenous) model identification has received considerable attention in last three decades. However, in a high‐order nonlinear system, it is very difficult to obtain the model structure directly even with state‐of‐art algorithms, because the number of candidate monomial terms is huge and increases drastically as the model order increases. Motivated by this fact, in this research, the identification is performed in two steps: firstly a prescreening process is carried out to select a reasonable number of important monomial terms based on two kinds of the importance indices. Then, in the reduced searching space with only the selected important terms, multi‐objective evolutionary algorithm (MOEA) is applied to determine a set of significant terms to be included in the polynomial model with the help of independent validation data. In this way, the whole identification algorithm is implemented efficiently. Numerical simulations are carried out to demonstrate the effectiveness of the proposed identification method. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Modelling of lossy curved surfaces in the 3‐D frequency‐domain finite‐difference methods

A conformal first‐order or Leontovic surface‐impedance boundary condition (SIBC) for the modelling of fully three‐dimensional (3‐D) lossy curved surfaces in a Cartesian grid is presented for the frequency‐domain finite‐difference (FD) methods. The impedance boundary condition is applied to auxiliary tangential electric and magnetic field components defined at the curved surface. The auxiliary components are subsequently eliminated from the formulation resulting in a modification of the local permeability value at boundary cells, allowing the curved 3‐D surface to be described in terms of Cartesian grid components. The proposed formulation can be applied to model skin‐effect loss in time‐harmonic driven problems. In addition, the impedance matrix can be used as a post‐processor for the eigenmode solver to calculate the wall loss. The validity of the proposed model is evaluated by investigating the quality factors of cylindrical and spherical cavity resonators. The results are compared with analytic solutions and numerical reference data calculated with the commercial software package CST Microwave Studio™ (MWS). The convergence rate of the results is shown to be of second‐order for smooth curved metal surfaces. The overall accuracy of the approach is comparable to that of CST MWS™. Copyright © 2006 John Wiley & Sons, Ltd.     

A fuzzy C‐regression model algorithm using a new PSO algorithm

In this paper, a new methodology is introduced for the identification of the parameters of the multiple‐input–multiple‐output local linear Takagi‐Sugeno fuzzy models using the weighted recursive least squares (WRLS). The WRLS is sensitive to initialization, which leads to no convergence. In order to overcome this problem, adaptive chaos particle swarm optimization is proposed to optimize the initial states of WRLS. This new algorithm is improved versions of the original particle swarm optimization algorithm. Finally, comparative experiments are designed to verify the validity of the proposed clustering algorithm and the Takagi‐Sugeno fuzzy model identification method, and the results show that the new method is effective in describing a complicated nonlinear system with significantly high accuracies compared with approaches in the literature.     

A combined approach for the identification of continuous non‐linear systems

The identification of a non‐linear continuous output‐only system from a time series is considered for the case that the functional form of the model is not known beforehand. To estimate both functions and parameters, a combination of non‐parametric modelling based on non‐linear regression and parametric modelling based on a multiple shooting algorithm is proposed. This strategy to determine non‐linear differential equations is exemplified on experimental data from a chaotic circuit where an accurate reconstruction of the observed attractor is obtained. Copyright © 2003 John Wiley & Sons, Ltd.     

A modified finite‐difference time‐domain method for analysing field‐to‐transmission line coupling of telecommunication system signals

A modified finite‐difference time‐domain (FDTD) code is presented for the line response characterization of a transmission line illuminated by a Gaussian pulse‐modulated electromagnetic signal. The final expressions are transformed according to the complex‐envelope representation in order to omit the high‐frequency carrier contribution and thus provide an accurate solution of the coupling phenomenon by avoiding the computational burden of the conventional FDTD algorithm. Comparison results between the conventional FDTD method and the modified one are presented, showing the advantages of the novel method. Copyright © 2002 John Wiley & Sons, Ltd.     

Robust adaptive phase‐only beamforming algorithm for interference suppression

The adaptive phase‐only beamforming technique is very important for suppressing interferences in phased array radar. However, similar to the conventional beamforming technique, which features variable magnitudes and phases, the performance of phase‐only beamforming is severely degraded by steering direction and array geometry errors. No studies on this problem are available. In this paper, the problem of adequate robustness for adaptive phase‐only beamformers is investigated, and a robust phase‐only beamforming algorithm based on semidefinite relaxation is proposed. This algorithm can suppress interferences by minimizing the array output power and maintain the desired signal without distortion. Robust adaptive phase‐only weighting is first converted into a non‐convex quadratic optimization problem and then into a convex optimization problem by the semidefinite relaxation technique, which can be solved easily. Experimental results demonstrate that the new robust adaptive phase‐only beamforming algorithm can significantly reduce performance degradation caused by various array errors. Copyright © 2014 John Wiley & Sons, Ltd.     

A matrix‐exponential decomposition‐based time‐domain method for band structure calculation of one‐dimensional periodic structures

A time‐domain method for calculating the band structure of one‐dimensional periodic structures is proposed. During the time‐stepping of the method, the column vector containing the spatially sampled field data is updated by multiplying with an iteration matrix. The iteration matrix is first obtained by using the matrix‐exponential decomposition technique. Then, the small nonzero elements of the matrix are pruned to improve its sparse structure, so that the efficiency of the matrix–vector multiplication involved in each time‐step is enhanced. The numerical results show that the method is conditionally stable but is much more stable than the conventional finite‐difference time‐domain (FDTD) method. The time‐step with which the method runs stably can be much larger than the Courant–Friedrichs–Lewy (CFL) limit. And moreover, the method is found to be particularly efficient for the band structure calculation of large‐scale structures containing a defect with a very high wave speed, where the conventional FDTD method may generally lose its efficiency severely. For this kind of structures, not only the stability requirement can be significantly relaxed, but also the matrix‐pruning operation can be very effectively performed. In the numerical experiments for large‐scale quasi‐periodic phononic crystal structures containing a defect layer, significantly higher efficiency than the conventional FDTD method can be achieved by the proposed method without an evident accuracy deterioration if the wave speed of the defect layer is relatively high. Copyright © 2016 John Wiley & Sons, Ltd.     

900 MHZ radio‐frequency identification rectifier with optimization and reusing of electro‐static discharges protections in 180 nm digital CMOS technology

Sensitivity and electro‐static discharges (ESD) protection level are crucial parameters for any Ultra High‐Frequency (UHF) power rectifier–harvester designed for radio‐frequency identification (RFID) devices. While sensitivity limits the reading range of the interrogator‐to‐tag communication link, the requirement for an adequate protection against ESD is enforced in commercial devices connected to a printed antenna. Both resistive and capacitive parasitics of the protection circuits severely affect RF performance of the device. In the paper, a rectifier for UHF RFID embedding an ESD protection for 2 kV human‐body discharge model (HBM) level is proposed. The target of a low added parasitic capacitance is achieved by adapting the protection circuit to the RFID rectifier and reusing the ESD clamp for additional functions being mandatory in a UHF RFID front end. The layout of the ESD clamp has been optimized for minimum parasitic resistance without sacrificing the protection level. Two UHF harvesters were implemented in a 180 nm digital complementary metal‐oxide semiconductor (CMOS) technology, featuring a minimum sensitivity of ?15.5 dBm with an ESD protection level of 2 kV HBM. Copyright © 2014 John Wiley & Sons, Ltd.     

一种文化鱼群算法及其在电机参数辨识中的应用

针对基本鱼群算法盲目搜索的问题,提出一种新的基于知识的带变异算子的人工鱼群算法。利用文化算法的框架,将鱼群算法嵌入到种群空间当中,构造适用于文化鱼群算法的新的影响函数。同时应用信念空间中的规范知识和情境知识通过影响函数指导人工鱼群算法中的进化步长和方向。通过高维多峰函数检验新算法的性能,最后将新算法应用于一台内置有执行器的鼠笼电机系统的参数辨识问题,得到了参数化的执行器-转子模型。仿真结果表明新算法与基本鱼群算法相比性能显著提高,并且能够有效地解决工程优化问题。     

A study on the tie‐set graph theory and network flow optimization problems

Aiming at establishing a firm basic theory to ring‐based information network management systems, our paper proposes a tie‐set graph theory. We define a binary vector representing a tie‐set in a biconnected undirected graph G=(V,E) as a tie‐set vector. The set of tie‐set vectors forms a vector space over the proposed law of composition, then a basis of the vector space, μ linear independent tie‐set vectors, is defined as a tie‐set basis. The essential key concept in our theory is a tie‐set graph, which has a one‐to‐one correspondence to a tie‐set basis and represents a relation between two tie‐set vectors of the basis. Some important properties of tie‐set graphs and their application to survivable mesh networks in modern high‐speed backbone networks are also presented. Furthermore, as a general approach to network flow optimization problems, tie‐set flow vector space is proposed based on the tie‐set graph theory. A distributed algorithm for the network flow optimization problems and its application are also presented in this paper. Copyright © 2004 John Wiley & Sons, Ltd.