Frequency response

About: Frequency response is a research topic. Over the lifetime, 25705 publications have been published within this topic receiving 332249 citations.

Fast Frequency Response From Offshore Multiterminal VSC–HVDC Schemes

Abstract: This paper analyzes the frequency support characteristics of multiterminal voltage source converter HVdc (VSC–HVdc) (MTDC) schemes using the energy transferred from wind turbine rotating mass and other ac systems. An alternative coordinated control (ACC) scheme that gives priority to a frequency versus active power droop fitted to onshore VSCs is proposed to: transfer wind turbine recovery power to undisturbed ac grids, and allow correct control operation of MTDC systems during multiple power imbalances on different ac grids. The fast frequency response capability of MTDC systems equipped with the proposed ACC scheme is compared against a coordinated control scheme, which uses a frequency versus dc voltage droop. The frequency control schemes are demonstrated on an experimental test rig, which represents a three-terminal HVdc system. Also, the MTDC frequency support capability when wind farms do not provide extra power is tested using a four-terminal HVdc system.

Taylor–Kalman–Fourier Filters for Instantaneous Oscillating Phasor and Harmonic Estimates

Abstract: Recently, the TaylorK Kalman filter was proposed for estimating instantaneous oscillating phasors. Its performance was examined through time-domain simulations using the benchmark test signals specified in the IEEE Standard for Synchrophasors for Power Systems. It was discovered that the estimation error level was abruptly reduced by a factor of ten from the second order, mainly because those filters were able to provide instantaneous phasor estimates. In this paper, the frequency response of the zeroth- and second-order filters is established and illustrated. They demonstrate that, for orders greater than or equal to two, the filters are able to form zero flat phase response about the operation frequency and then able to provide instantaneous estimates. By assessing the behavior of the estimates before signals with harmonics, or noise, not contemplated in the signal model, the frequency response method leads us to design more robust filters, referred to as TaylorK Kalman-Fourier, because they incorporate the whole set of harmonics in their multiharmonic signal model. It turns out that the bank of comb filters achieved with K = 0 is equivalent to that of the discrete Fourier transform, with a computational cost of one and a half products per harmonic estimate, which is lower than the FFT cost for more than eight components, and the bank of fence filters obtained with K = 2 is similar to that of the Taylor2 Fourier transform but with the advantage of providing estimates devoid of delay and needing only four products per harmonic set of estimates. Due to their instantaneous character, and computational simplicity, those estimates are certainly very useful for real-time harmonic analysis and power system control applications.

Dynamic measuring of frequency and frequency oscillations in multiphase power systems

Abstract: Instantaneous system frequency is defined, and a method of frequency measurement is proposed which determines the angular velocity of the rotating voltage space phasor. Impulses in frequency caused by steps in phase are blanked out, whereas harmonics and noise are suppressed by FIR filters. Using an optimized observer-based filter, frequency modulations are split into and frequency drift and frequency oscillation signals, which can be used in power control and power system stabilization. >

Evaluation of an algorithm for the assessment of the MTF using an edge method.

Abstract: An algorithm to calculate the presampling modulation transfer function (MTF) of an imaging system from an angled edge image has its own inherent transfer function. Factors such as the angle of the sampling aperture to the edge, registration of edge function profiles using the determined edge angle, differentiation, smoothing, and folding all combine to produce the frequency response of the algorithm. In this work, the profile registration transfer function accounting for an error in the determined edge angle has been derived. This has been incorporated with other, previously reported, algorithm component transfer functions to fully characterize the MTF calculation algorithm. When registering profiles, small errors in the edge angle determination were found to result in large errors in the MTF, as the misalignment errors increase with the number of profiles. For example, registering 50 profiles a 0.07 degree error in a 7 degree edge angle (1% error) produces a 36% error in the MTF at the system cutoff frequency f=f(c) when profiles are oversampled at a frequency f(s)=8f(c)(f(c) is defined as the maximum frequency reproducible without aliasing when sampling at the limiting system Nyquist frequency f(s) = 2f(c)). These results highlight the importance of quantifying the transfer function of the algorithm used to determine an imaging system modulation transfer function. The MTF calculation algorithm and the transfer function analysis have been incorporated into a Windows-based software program to be made available for general use.

High bandwidth passive integrated circuit tester probe card assembly

Abstract: Described herein is a probe card assembly providing signal paths for conveying high frequency signals between bond pads of an integrated circuit (IC) and an IC tester. The frequency response of the probe card assembly is optimized by appropriately distributing, adjusting and impedance matching resistive, capacitive and inductive impedance values along the signal paths so that the interconnect system behaves as an appropriately tuned Butterworth or Chebyshev filter.