Equivalent Network Parameters Research Articles

ADMoE: Anomaly Detection with Mixture-of-Experts from Noisy Labels

Existing works on anomaly detection (AD) rely on clean labels from human annotators that are expensive to acquire in practice. In this work, we propose a method to leverage weak/noisy labels (e.g., risk scores generated by machine rules for detecting malware) that are cheaper to obtain for anomaly detection. Specifically, we propose ADMoE, the first framework for anomaly detection algorithms to learn from noisy labels. In a nutshell, ADMoE leverages mixture-of-experts (MoE) architecture to encourage specialized and scalable learning from multiple noisy sources. It captures the similarities among noisy labels by sharing most model parameters, while encouraging specialization by building "expert" sub-networks. To further juice out the signals from noisy labels, ADMoE uses them as input features to facilitate expert learning. Extensive results on eight datasets (including a proprietary enterprise security dataset) demonstrate the effectiveness of ADMoE, where it brings up to 34% performance improvement over not using it. Also, it outperforms a total of 13 leading baselines with equivalent network parameters and FLOPS. Notably, ADMoE is model-agnostic to enable any neural network-based detection methods to handle noisy labels, where we showcase its results on both multiple-layer perceptron (MLP) and the leading AD method DeepSAD.

Specific aspects of forecasting electrical energy losses in electricity networks

The present paper considers methods of predicting load losses under varied types of electrical energy loss characteristics. The method of forecasting electrical energy losses with the use of one-factor (planned electrical supply to network) and multi-factor (planned values of electrical supply to network, energy output from electric power stations, etc.) characteristics of power and energy losses is proposed. Static models of nodal loads and parameters of equivalent network are used. The paper substantiates the application of multi-factor characteristics for assessing electrical energy losses during regulatory period. The paper provides the solution of the system of nonlinear equations describing long-term balance plans for electrical energy and gives the results of predicting load losses of electrical energy.

Novel voltage-to-power sensitivity estimation for phasor measurement unit-unobservable distribution networks based on network equivalent

The access and application of phasor measurement units (PMUs) in distribution networks highly improve the system observability and further enhance the performance of operation control and energy management. A novel PMU-based estimation method of voltage-to-power sensitivity via network equivalent is proposed for distribution systems. An equivalent model is introduced to simplify the PMU-unobservable parts of the distribution network. The equivalent parameters are estimated with the PMU measurements on both sides. The original PMU-unobservable distribution network is simplified into a completely observable network with an arbitrary configuration of PMUs. The maximum correntropy Kalman filter (MCKF) is exploited in parameter estimation to handle the noise and bad data within the PMU measurements. The voltage-to-power sensitivity of the simplified system is then calculated according to the estimation of the equivalent network parameters. Case studies on the IEEE 33-node and the PG&E 69-node test feeders verify the correctness and effectiveness of the proposed method.

Concurrent Real-Time Estimation of State of Health and Maximum Available Power in Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are an emerging energy storage technology with higher performance than lithium-ion batteries in terms of specific capacity and energy density. However, several scientific and technological gaps need to be filled before Li-S batteries will penetrate the market at a large scale. One such gap, which is tackled in this paper, is represented by the estimation of state-of-health (SOH). Li-S batteries exhibit a complex behaviour due to their inherent mechanisms, which requires a special tailoring of the already literature-available state-of-charge (SOC) and SOH estimation algorithms. In this work, a model of SOH based on capacity fade and power fade has been proposed and incorporated in a state estimator using dual extended Kalman filters has been used to simultaneously estimate Li-S SOC and SOH. The dual extended Kalman filter’s internal estimates of equivalent circuit network parameters have also been used to the estimate maximum available power of the battery at any specified instant. The proposed estimators have been successfully applied to both fresh and aged Li-S pouch cells, showing that they can accurately track accurately the battery SOC, SOH, and power, providing that initial conditions are suitable. However, the estimation of the Li-S battery cells’ capacity fade is shown to be more complex, because the practical available capacity varies highly with the applied current rates and the dynamics of the mission profile.

A Practical Equivalent Method for DFIG Wind Farms

With increasing penetration of wind power, it is recognized that manufacturer-specific models of wind turbines are not appropriate for power system studies, and the equivalent model of wind farms required by dynamic modeling poses a complicated technical challenge. In this paper, a practical equivalent method for wind farms with doubly fed induction generator (DFIG) wind turbines is proposed. Three critical steps are involved in this method. Step 1, modeling of a wind turbine, the model incorporating the complete fault ride through process is constructed and validated for an operational DFIG wind turbine. Step 2, clustering of wind turbines, a practical four-machine equivalent method is proposed. Initially, dynamic responses of active power of a DFIG wind turbine operating at various wind speeds are investigated to obtain three clusters of wind turbines, then four clusters are further determined by improving equivalency error at some typical wind speed scenarios. Step 3, an analytical method is proposed to determine the equivalent collector network parameters for each of the four equivalent machines. The proposed method is validated by comparing with the single-machine representation and the detailed wind farm model. Simulation results show that the proposed method has good performance for different fault durations, voltage dips, and changing wind scenarios.

Investigation of the Overvoltage and Fast Transient Phenomena on Transformer Terminals by Taking Into Account the Grounding Effects

A large number of electromagnetic transient studies have so far reported findings related to the overvoltage behavior of systems within a broad frequency range. However, in most cases, actual grounding effects have been either not taken into account or have been just partially considered. Although an accurate methodology to study grounding effects exists, a detailed analysis of the grounding effects has not yet been fully performed. Moreover, many test applications are performed in laboratories where the grounding is close to ideal. In this paper, the grounding system modeling methodology is described, and its capability is demonstrated for an existing complex grounding system. First, the complex grounding system is modeled in the frequency domain by the TRAGSYS program, which represents the grounding system as an equivalent multiport network. Next, the equivalent network parameters are represented in a broad frequency range enabling time domain computations in ATP-EMTP. Finally, the protection level of the chosen lightning arresters is discussed under most severe conditions.

Electromagnetic Modeling of Through-Silicon Via (TSV) Interconnections Using Cylindrical Modal Basis Functions

This paper proposes an efficient method to model through-silicon via (TSV) interconnections, an essential building block for the realization of silicon-based 3-D systems. The proposed method results in equivalent network parameters that include the combined effect of conductor, insulator, and silicon substrate. Although the modeling method is based on solving Maxwell's equation in integral form, the method uses a small number of global modal basis functions and can be much faster than discretization-based integral-equation methods. Through comparison with 3-D full-wave simulations, this paper validates the accuracy and the efficiency of the proposed modeling method.

Novel applications of Z -matrix to network topology analysis in the relay coordination software

The impedance matrix (Z-matrix) of power system contains much useful and unrevealed information. It has been widely used for short-circuit analysis, contingency analysis and economic dispatch. Based on the electrical coupling paths described by physical parameters of equivalent network derived from the reduced impedance matrix, some novel physical topological analysis methods to identify cut edges, cut vertices and radial paths in the relay coordination and fault analysis software are proposed. The formation of the impedance matrix is the fundamental work of the fault analysis and relay coordination. The physical methods proposed thoroughly utilise the topological information concealed in the existent Z-matrix. Compared with the traditional graph-theoretical approaches, the physical one has clearer and more significant physical implication that may help to understand and give insight into the study of the topology of the electrical network topology in power system comprehensively. Examples are presented to prove the consistency of physical topology in power system with the corresponding geometrical topology. The efficiency of the physical methods to improve network topology analysis has also been validated.

CHARACTERISTICS OF AN OFFSET LONGITUDINAL / TRANSVERSE SLOT COUPLED CROSSED WAVEGUIDE JUNCTION USING MULTIPLE CAVITY MODELING TECHNIQUE CONSIDERING THE TE00 MODE AT THE SLOT APERTURE

A moment method analysis of a broad wall slot coupled crossed rectangular waveguide junction has been presented in this paper. The coupling slot is longitudinal/transverse and offset from the centre lines of the guides. The integral equations, governing the characteristics of the device, have been obtained using Multiple Cavity Modeling Technique, taking into account of the finite wall thickness and the TE00 mode at the slot apertures and have been solved using Moment Method to obtain the aperture distribution. The normalized resonant lengths/complex S-parameters have been calculated from this field distribution for different guide height/slot offsets/slot widths/slot thickness of the longitudinal/transverse slot over the frequency band. Numerical data, thus obtained, have been compared with measured/literature available/CST Microwave Studio Simulated data. The theory has been validated by the reasonable agreement obtained between them. It has been shown that, neglecting the TE00 mode at the slot apertures can adversely effect the estimation of the resonant frequency and equivalent network parameters.

Analysis of Inclined I-Slots in the Narrow Wall of Standard X-Band Rectangular Waveguide

Different types of slot configurations in one of the walls of rectangular waveguides are analyzed by different researchers. In this paper different configurations of inclined I-slot radiators have been investigated and analysed. The analysis consists of evaluation of admittance characteristics of the slot as a function of slot parameters and frequency. Slot admittance characteristics are obtained from the concepts of self-reaction and discontinuity in modal current. On the other hand, coupling and VSWR are evaluated from the shunt equivalent network parameter making use of transmission matrix approach. The variations of normalized conductance, susceptance, coupling and VSWR as a function of frequency are presented. The advantage of such types of slots is that the entire slot geometry is confined only to narrow wall.

Construction of power system load models and network equivalence using an evolutionary computation technique

This paper presents a novel methodology using an evolutionary computation technique for power system load modelling. The proposed method provides a network equivalence approach, which can considerably reduce the complexity of the transmission and distribution networks to provide an area load model based on the load models recommended by IEEE. An improved genetic algorithm is used to estimate the model and equivalent network parameters with introduction of fictitious transmission lines and load buses. To demonstrate an application of the method, a simulation study of a 5-bus power system subject to a variety of disturbances has been used to provide the source of primary data. The results show that the system behaviour can be accurately replicated by the equivalent area load model with parameters derived using the proposed methodology.

Optimization of gate-to-drain separation in submicron gate-length modulation doped FET's for maximum power gain performance

This paper analyzes the effects of the separation between the gate and the drain electrodes on the high-frequency performance limitations of heterostructure MODFET's. Based on the effective gate-length and carrier velocity saturation concepts first the key small-signal equivalent network model parameters of the MODFET are calculated. The concept of open-circuit voltage gain, defined as the transconductance to output conductance ratio (g/sub m//g/sub o/), has been exploited to determine the output conductance with a knowledge of the static electric field and potential at the edge of the gate on the drain side. By treating the c/sub o//spl mu//sub n/ product as a function of the gate voltage, the drain current-voltage and transconductance characteristics have been effectively modeled for practical devices. By combining the effects of the intrinsic and parasitic equivalent network parameters this paper has determined the dependence of the g/sub m//g/sub o/ ratio, the gate capacitance to the feedback capacitance ratio, the unity current gain frequency (f/sub r/) and the maximum frequency of oscillations (f/sub max/) on the gate-to-drain separation (L/sub gd/). MODFET's based on InAlAs/InGaAs heterostructures lattice-matched to InP substrate with gate-length values of 0.25 /spl mu/m, 0.15 /spl mu/m and 0.1 /spl mu/m are considered for analyses. The optimum values of L/sub gd/ calculated are 600 /spl Aring/, 420 /spl Aring/, and 340 /spl Aring/ for the corresponding maximum f/sub max/-values of 250, 370, and 480 GHz, respectively.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Electromagnetic coupling through a wire-penetrated small aperture in and infinite conducting plane

The electromagnetic coupling of an incident plane wave through an electrically small aperture, penetrated by a wire, in an infinite conducting screen is considered. An equivalent-circuit model for the analysis of the wire-aperture coupling is developed using Norton's equivalence theorem. The method of moments is used to find the equivalent network parameters in the model. Numerical results are presented for several cases of interest.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Electrical Characteristics of an Inclined Strip Extending Between the Broadwalls of a Rectangular Waveguide

A moment method formulation of the determination of the equivalent network parameters of an inclined strip extending between the opposite broad walls of a rectangular waveguide is given in this paper. The integral equation representing the boundary condition of the tangential component of electric field along the length of the strip is converted into a matrix equation using a pulse function and point matching technique. From a knowledge of the coefficients of the basis function, the complex reflection coefficient and hence the equivalent network parameter is determined. Comparison between the theoretical and the experimental results is also presented. The perturbation of the wall current in the vicinity of the obstacle is also studied.

Scattering Characteristics of a Slot-Coupled T-Junction between Rectangular and Circular Waveguides

The scattering coefficients of a T-junction between rectangular and circular waveguides, coupled through a longitudinal slot in the narrow wall of the rectangular waveguide, are determined using moment method formulation, for excitation applied to the rectangular guide. The amplitude coefficients of the slot field distribution, computed in the process of determining the scattering coefficients, are used for the evaluation of the field distribution in the aperture plane of the coupling slot. The reflection and transmission coefficients, coupling as well as the equivalent network parameters are evaluated from the scattering coefficients, taking the effect of wall thickness into account. Comparison between the theoretical and experimental results on coupling and VSWR are presented.

Analysis of E-H plane tee junction using a variational formulation

A three-port equivalent network for an E-H plane tee junction is determined taking into account the effect of waveguide wall thickness and considering the contribution of the dominant mode to the imaginary part of the self-reaction. The parameters of the three-port equivalent network are determined. From a knowledge of the equivalent network parameters, the net impedance loading, reflection coefficient, and coupling are evaluated for an E-H plane tee junction. A comparison between theoretical and experimental results is also presented. >

Adaptive, closed-loop control of dynamic power filters as fictitious power compensators

A new control philosophy, utilizing both thyristor-controlled reactive (TCR) sources and dynamic power filters (DPFs) has been proposed by J.H.R. Enslin and J.D. Van Wyk (IEEE Trans. Power Electron., vol.5, no.1, 1990) in the application of fictitious power compensation. This study shows the closed-loop control of a DPF using an adaptive signal processing algorithm based on the cross-correlation between the voltage and current waveforms. The control strategy is based on the derivation of equivalent network parameters, which are calculated from digital time domain cross-correlation signal processing techniques and implemented with the aid of a microcomputer. Practical results under quasidynamic operating conditions obtained from a 15 kVA three-phase dynamic power filter are given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

S matrix of slot-coupled H-plane tee junction using rectangular waveguides

Complex scattering matrix parameters of a slot-coupled, waveguide tee junction are determined using a moment method of analysis with entire orthogonal basis functions and a rigorous analysis of the effect of wall thickness. The variations of the equivalent network parameter, coupling, and return loss with frequency are evaluated, and the results are compared with experimental data. The unitary property of the S matrix is verified. The dependence of coupling on slot length, slot width, and thickness is presented. >

Technical memorandum: Analysis of reactively loaded microstrip disk antenna

The moment method solution to the problem of a reactively loaded circular patch is presented. Using the reaction integral equation in conjunction with the method of moments, parameters of the Thévenin&apos;s equivalent network for the loaded patch are obtained. From the equivalent network parameters an expression for the input impedance of the loaded patch is derived. A design procedure for a circularly polarised disk antenna is presented. Computed results are compared with the experimental data.

A new approach to the definition of electric power, under conditions of distorted voltages and currents

A generalized time-domain definition of electric power, using autocorrelation and cross-correlation techniques, is proposed for measurement, characterization and compensation of fictitious power in any network, under conditions of nonsinusoidal and in general aperiodic voltage and current waveforms. This leads to the proposal of a new equivalent network parameter, disseptance, which describes the nonlinear properties of the load. The problems associated with the existing definitions of electric power are pointed out by means of a descriptive summary of the different power definitions and their associated limitations. A new philosophy for compensation of fictitious power in distorted supplies, is based on this definition of power and network parameters.