Improved Frequency-Domain Steady-State Modeling of the Dual-Active-Bridge Converter Considering Finite ZVS Transition Time Effects

2020 ◽  
pp. 1-1
Author(s):  
Michael D'Antonio ◽  
Shiladri Chakraborty ◽  
Alireza Khaligh
Keyword(s):  
Steady State ◽  
Frequency Domain ◽  
Transition Time ◽  
Time Effects ◽  
Dual Active Bridge

Motion in frequency domain for harmonic balance simulation of electrical machines

2018 ◽  
Vol 37 (4) ◽  
pp. 1449-1460
Author(s):  
Markus Wick ◽  
Sebastian Grabmaier ◽  
Matthias Juettner ◽  
Wolfgang Rucker
Keyword(s):  
Steady State ◽  
Frequency Domain ◽  
Efficient Method ◽  
Harmonic Balance ◽  
Eddy Currents ◽  
Computational Effort ◽  
Electrical Machines ◽  
Accurate Approximation ◽  
Content Type ◽  
Magnetic Devices

Purpose The high computational effort of steady-state simulations limits the optimization of electrical machines. Stationary solvers calculate a fast but less accurate approximation without eddy-currents and hysteresis losses. The harmonic balance approach is known for efficient and accurate simulations of magnetic devices in the frequency domain. But it lacks an efficient method for the motion of the geometry. Design/methodology/approach The high computational effort of steady-state simulations limits the optimization of electrical machines. Stationary solvers calculate a fast but less accurate approximation without eddy-currents and hysteresis losses. The harmonic balance approach is known for efficient and accurate simulations of magnetic devices in the frequency domain. But it lacks an efficient method for the motion of the geometry. Findings The three-phase symmetry reduces the simulated geometry to the sixth part of one pole. The motion transforms to a frequency offset in the angular Fourier series decomposition. The calculation overhead of the Fourier integrals is negligible. The air impedance approximation increases the accuracy and yields a convergence speed of three iterations per decade. Research limitations/implications Only linear materials and two-dimensional geometries are shown for clearness. Researchers are encouraged to adopt recent harmonic balance findings and to evaluate the performance and accuracy of both formulations for larger applications. Practical implications This method offers fast-frequency domain simulations in the optimization process of rotating machines and so an efficient way to treat time-dependent effects such as eddy-currents or voltage-driven coils. Originality/value This paper proposes a new, efficient and accurate method to simulate a rotating machine in the frequency domain.

Frequency-domain analysis method for analyzing and improving the steady-state characteristics of microcantilever in tapping-mode atomic force microscopy

2018 ◽  
Vol 82 (1) ◽  
pp. 10701
Author(s):  
Xiaohui Gu ◽  
Lining Sun ◽  
Changhai Ru
Keyword(s):  
Steady State ◽  
Frequency Domain ◽  
Stability Margin ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
System Stability ◽  
Analysis Method ◽  
External Interference ◽  
Tapping Mode ◽  
The Stability

In tapping-mode AFM, the steady-state characteristics of microcantilever are extremely important to determine the AFM performance. Due to the external excitation signal and the tip-sample interactions, the solving process of microcantilever motion equation will become very complicated with the traditional time-domain analysis method. In this paper, we propose the novel frequency-domain analysis method to analyze and improve the steady-state characteristics of microcantilever. Compared with the previous methods, this new method has three prominent advantages. Firstly, the analytical expressions of amplitude and phase of cantilever system can be derived conveniently. Secondly, the stability of the cantilever system can be accurately determined and the stability margin can be obtained quantitatively in terms of the phase margin and the magnitude margin. Thirdly, on this basis, external control mechanism can be devised quickly and easily to guarantee the high stability of the cantilever system. With this novel method, we derive the frequency response curves and discuss the great influence of the intrinsic parameters on the system stability, which provides theoretical guidance for selecting samples to achieve better AFM images in the experiments. Moreover, we introduce a new external series correction method to significantly increase the stability margin. The results indicate that the cantilever system is no longer easily disturbed by external interference signals.

An Advanced Frequency-Domain Code for BWR Stability Analysis and Design

2013 ◽  
Author(s):  
Behrooz Askari ◽  
George Yadigaroglu
Keyword(s):  
Steady State ◽  
Frequency Domain ◽  
Transfer Functions ◽  
Density Wave ◽  
System Stability ◽  
Reactor Kinetics ◽  
Analysis And Design ◽  
Drift Flux ◽  
Reactor Transfer ◽  
Phase Instabilities

Density Wave Oscillations in BWRs are coupled with the reactor kinetics. A new analytical, frequency-domain tool that uses the best available models and methods for modeling BWRs and analyzing their stability is described. The steady state of the core is obtained first in 3D with two-group diffusion equations and spatial expansion of the neutron fluxes in Legendre polynomials. The time-dependent neutronics equations are written in terms of flux harmonics (nodal-modal equations) for the study of “out-of-phase” instabilities. Considering separately all fuel assemblies divided into a number of axial segments, the thermal-hydraulic conservation equations are solved (drift-flux, non-equilibrium model). The thermal-hydraulics are iteratively fully coupled to the neutronics. The code takes all necessary information from plant files via an interface. The results of the steady state are used for the calculation of the transfer functions and system transfer matrices using extensively symbolic manipulation software (MATLAB). The resulting very large matrices are manipulated and inverted by special procedures developed within the MATLAB environment to obtain the reactor transfer functions that enable the study of system stability. Applications to BWRs show good agreement with measured stability data.

scholarly journals A Fast Frequency Domain Method for Steady-State Solution of Forced Vibration of System with Complex Damping

2020 ◽  
Vol 10 (10) ◽  
pp. 3442
Author(s):  
Wenrui Qi ◽  
Danguang Pan ◽  
Yongtao Gao ◽  
Wenyan Lu ◽  
Ying Huang
Keyword(s):  
Fourier Transform ◽  
Fourier Series ◽  
Steady State ◽  
Frequency Domain ◽  
Imaginary Part ◽  
Complete Solution ◽  
Time History ◽  
Frequency Domain Method ◽  
Domain Method ◽  
Complex Damping

The conventional frequency domain method (CFDM) and dual-force-based time domain method (DTDM) are often used to solve the steady-state response of system with complex damping under an arbitrary force. However, the calculation efficiency of the DTDM is low due to the straightforward summation operation of series even if the solution of the DTDM is the exact real part of the solution. In addition, since the CFDM only can obtain the real part of solution not the complete solution, it gives misleading information that the solution does not have an imaginary part. In this paper, a fast frequency domain method (FFDM) is proposed to calculate the complete response of complex damping system including the imaginary part with a higher accuracy in a much faster manner. The new FFDM uses half of the Fourier series of the discrete Fourier transform of the actual arbitrary force to construct the Fourier series of the dual force, followed by calculating the time history response using the inverse fast Fourier transform. The new developed method is validated through three numerical examples with harmonic and seismic excitations. The numerical results show that the accuracy of the new FFDM is compatible to the DTDM but with much higher computational efficiency.

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