Delay Cancellation Research Articles

A fault ride-through strategy for grid-forming converters under symmetrical and asymmetrical grid faults

In order to maintain grid-forming converter (GFM) voltage source behaviour under current limiting mode, a threshold virtual impedance (TVI) current limiting control is proposed, which is controlled in the positive and negative sequence synchronous reference frames for symmetrical and asymmetrical fault conditions. The converter current is strictly limited within the maximum limit without the need for current saturation limiters. Since the TVI control is based on 3-phase sinusoidal currents, it is shown that using the measured current instead of the existing current reference for the TVI control may cause oscillatory behaviour when a large switching delay is considered. Since sequence extraction control is necessary, the paper also compares GFM dynamic stability under the three well-known sequence extraction methods (i.e. delay cancellation, dual second order generalized integrator, and decoupled double synchronous reference frame). It is shown that the differences are small when GFM is not in current limiting mode, but they are large when GFM is in current limiting mode or switching delays are considered.

Development and Simulation of a Fast Delay Cancellation Algorithm for Digital Multimedia Network Communication

The digital multimedia network data traffic is huge, and many end devices are applied to the digital multimedia network; therefore, the digital media network communication delay transmission must be analysed in order to improve the performance of the digital multimedia network communication transmission. Due to the presence of a large number of data packets in the communication network used, some random delays in data can occur during use. Conventional data transmission methods rely solely on extended data storage capacity to achieve this, making it difficult to achieve intelligent scheduling, resulting in delays and optimized performance degradation during communication data transmission. The aim of this paper is to enhance the communication quality of digital multimedia networks by developing an algorithmic model that rapidly mitigates communication delays. The proposed approach employs a delay cancellation algorithm in a network predictive control system. Simulation techniques are utilized to simulate and compensate for delays in multimedia communication networks. The efficacy of the network control strategy is demonstrated through simulation tests on a large-scale multimedia network communication system. The research findings indicate that the network control prediction model and elimination algorithm can substantially reduce the packet loss rate and quickly eliminate communication delays in digital multimedia networks.

Refraction of space-time wave packets: II. experiments at normal incidence.

The refraction of space-time (ST) wave packets offers many fascinating surprises with respect to conventional pulsed beams. In the first paper in this sequence [J. Opt. Soc. Am. A38, 1409 (2021)10.1364/JOSAA.430105], we theoretically described the refraction of all families of ST wave packets at normal and oblique incidence at a planar interface between two nondispersive, homogeneous, isotropic dielectrics. Here, in this second paper in the sequence, we present experimental verification of the refractive phenomena predicted for baseband ST wave packets upon normal incidence on a planar interface. Specifically, we observe group velocity invariance, normal and anomalous refraction, and group velocity inversion leading to group delay cancellation. These phenomena are verified in a set of optical materials with refractive indices ranging from 1.38 to 1.76, including MgF2, fused silica, BK7 glass, and sapphire. We also provide a geometrical representation of the physics associated with anomalous refraction in terms of the dynamics of the spectral support domain for ST wave packets on the surface of the light cone.

Design of Multi-Scale Negative Group Delay Circuit for Sensors Signal Time-Delay Cancellation

This paper develops an innovative method of sensors’ time-delay suppression. The proposed delay cancellation technique is highlighted with a theoretical concept and time-domain experimental demonstrations by using the negative group delay (NGD) function. The analytical investigation is elaborated with an NGD topology constituted by a simple active $RC$ network. It is established theoretically that this active cell behaves like a low-pass NGD topology. The synthesis equations enabling to calculate the NGD cell parameters as a function of the desired NGD and gain are formulated. Frequency- and time-domain analyses showing the NGD function in multi-time scale are discussed. The NGD function verification is fulfilled with the design and fabrication of a proof-of-concept prototype. Nano-, micro-, and milli-second NGD effects are numerically and experimentally proved. As expected, time-domain experimental demonstrations showing arbitrary waveform signal in outstanding time-advance are realized. Moreover, the feasibility of the signal delay cancellation with 1- and 8-m length cables is experimented. The developed NGD time-delay cancellation demonstrations open the potential applications for the sensor performance improvement.

A low-power relaxation oscillator with high frequency stability for RFID

A low-power relaxation oscillator with a high frequency stability is presented for radio frequency identification (RFID). This oscillator implements an improved self-biased and a comparator multiplexing techniques to reduce the power consumption and chip area. A capacitor resetting delay cancellation technique based on a two-phase operation and a proportional to absolute temperature (PTAT) current with an upward curvature versus the temperature are adopted to maintain the frequency stability. The oscillator is designed in a 65 nm standard CMOS process and occupies a small area of 0.0216 mm2. The post-layout simulation results show that a frequency drift of 0.95% from 0.7 to 1.7 V and a temperature stability of 27 ppm/°C as the temperature varies from − 40 to 85 °C at a typical working frequency of 1.92 MHz. Under a supply voltage of 0.7 V, the maximum power consumption is only 15.4 μW at − 40 °C. At room temperature, the figure of merit (FOM1 and FOM2) are 8 nW/kHz and 89.5 dB, respectively, which makes it more efficient than relaxation oscillators reported to date.

An integrated wind turbine failures prognostic approach implementing Kalman smoother with confidence bounds

This paper represents an integrated prognostics method dedicated to the wind turbine high-speed shaft bearing prognosis, which integrates physical degradation models and data driven approaches. In bearing failure prognostics, the excessive shaft vibration eventually leads to the system failure. In this case (crack growth prognostics), the measured data (crack size) is the same as a model prediction from Paris’s law. Indeed, we introduce an integrated prognostic approach based on usage model through Paris’s law and the use of a Kalman smoother to estimate the remaining useful life offering a solution to the inherent phase delay cancellation from Kalman filtering, providing a more accurate and smoother estimate with confidence bounds.The proposed method is validated on a real high-speed shaft bearing wind turbine generator. The used database contains one raw acquisition per day over 50 days of measurement at a high sample rate, 6 s each. The results show that the Kalman smoother is an effective way to improve trending and remaining useful life estimation.

Unbalanced voltage control of virtual synchronous generator in isolated micro-grid

Virtual synchronous generator (VSG) control is recommended to stabilize the voltage and frequency in isolated micro-grid. However, common VSG control is challenged by widely used unbalance loads, and the linked unbalance voltage problem worsens the power quality of the micro-grid. In this paper, the mathematical model of VSG was presented. Based on the analysis of positive- and negative-sequence equivalent circuit of VSG, an approach was proposed to eliminate the negative-sequence voltage of VSG with unbalance loads. Delay cancellation method and PI controller were utilized to identify and suppress the negative-sequence voltages. Simulation results verify the feasibility of proposed control strategy.

Analytical Design, Simulation & Evaluation of Proposed OCDMA with Message Priority Fast Routing Codes

In this paper, a new optimized class of optical codes known as Message priority & fast routing (MPFR) is presented. MPFR code is essential in the priority based communication of OCDMA for multiple user environments since these codes control the multiple access interface delay cancellation effectively. In proposed work, codes for MPFR are generated based on simple tridiagonal matrix with less size of the header bit reduction. In the proposed algorithm, multiple user environments have been used in accordance to the packet header. The message size is increased and priority bit is added which leads to faster and effective data transfer in communication. The transmitter use 2D codes, which is further added a priority bit for transmission. Our obtained results revealed that proposed MPFR codes provided better results compared to flexible cross correlation (FCC) codes, zero cross correlation (ZCC) codes and Prime Hop codes (PHC) in term of bit error rate, packet delivery ratio and multiple access interference.

Excess loop delay cancellation in sigma–delta modulators

Excess loop delay in sigma–delta ( $$\Sigma\Delta$$ ) modulators, especially by increasing the level of noise in signal bandwidth in continuous kind of them, leads to a dramatic decrease in their efficiency. In this paper, the error originated from the loop delay is calculated analytically and a new structure for sigma–delta modulators is presented based upon this calculation. This new structure can compensate the effect of loop-delay error completely independent of amount of delay. So by changing in loop delay during system working, the proposed structure has ability to consistent itself with new conditions and re-eliminate the error. This ability is independent of being multi-bit and the order of modulator. To evaluate the efficiency of the proposed method and the corresponding structure, first and second order modulators with capability of eliminating the error of loop delay, have been designed and simulated. All of simulations show the correctness of proposed analysis. Comparison of the proposed structures with the previous works shows the effectiveness of our technique.

A Study of Phase-Locked Technology of Wind Power Generation Three-Phase Grid-Connected Inverter

This paper presents two phase-locked methods of wind power generation three-phase grid-connected inverter. First establishes the mathematical model of the inverter, on this basis analyzes why the power voltage phase must be known. And then studies the direct calculation method in α-β coordinates, and analyzes the shortcomings of this approach for three-phase imbalance; then focusing on the phase locked loop (PLL) approach in d-q coordinate system. To solve dynamic response problem of the PLL, a new signal delay cancellation method is put forward. With this improved method, the PLL can have a better performance. Experimental results show that the theoretical analysis is real.

A time-based energy-efficient analog-to-digital converter

Dual-slope converters use time to perform analog-to-digital conversion but require 2/sup N+1/ clock cycles to achieve N bits of precision. We describe a novel current-mode algorithm that also uses time to perform analog-to-digital conversion but requires 5N clock cycles to achieve N bits of precision via a successive subranging technique. The algorithm requires one asynchronous comparator, two capacitors, one current source, and a state machine. Amplification of two is achieved without the use of an explicit amplifier by simply doing things twice in time. The use of alternating voltage-to-time and time-to-voltage conversions provides natural error cancellation of comparator offset and delay, 1/f noise, and switching charge-injection. The use of few components and an efficient mechanism for amplification and error cancellation allow for energy-efficient operation: in a 0.35-/spl mu/m implementation, we were able to achieve 12 bit of DNL limited precision or 11 bit of thermal noise-limited precision at a sampling frequency of 31.25 kHz with 75 /spl mu/W of total analog and digital power consumption. These numbers yield a thermal noise-limited energy efficiency of 1.17 pJ per quantization level, making it one of the most energy-efficient converters to date in the 10-12 bit precision range.

Input‐output linearization with delay cancellation for nonlinear delay systems: the problem of the internal stability

AbstractThis paper investigates the issue of the internal stability of nonlinear delay systems controlled with a feedback law that performs exact input–output, linearization and delay cancellation. In previous works the authors showed that, unlike with the case of systems without state delays, when the relative degree is equal to the number of state variables and the output is forced to be identically zero, delay systems still possess a non‐trivial internal state dynamics. Not only, in the same conditions delay systems are also characterized by a non‐trivial input dynamics. Obviously, both internal state and input dynamics should give bounded trajectories, otherwise the exact input–output linearization and delay cancellation technique cannot be applied. This paper studies the relationships between the internal state and input dynamics of a controlled nonlinear delay system. An interesting result is that a suitable stability assumption on the internal state dynamics ensures that, when the output is asymptotically driven to zero, both the state and control variables asymptotically decay to zero. Copyright © 2003 John Wiley & Sons, Ltd.

Anisochronic state observers for hereditary systems

The anisochronic observers result from a functional extension of the classical state space bringing a significantly reduced number of needed state variables, as compared with the standard approach. The anisochronic state variables can be selected as measurable outputs in most cases and their availability provides significant advantage in process monitoring. Observability condition is presented for anisochronic process models with arbitrary sort of delays. Since hereditary systems are considered a typical result of control system integration the issue of decomposition on separate units is followed in observer design. As a special aim, the observer design delay cancellation in the observation process is solved using a functional extension of Ackermann's formula for this purpose.

A case of caffeine-mediated cancellation of mitotic delay without enhanced breakage in V79 cells

Chinese hamster cells (V79 379A) were grown for 17 h in the presence of 10 μg/ml bromodeoxyuridine (BrdU) to obtain cells with potential sister-chromatid differentiation. At this time batches were irradiated (1.5 Gy, 250 kVp X-rays) and the medium of all flasks replaced with one containing 10 μg/ml thymidine with or without 400 μg/ml caffeine. Metaphases from irradiated and unirradiated batches were sampled every hour for 7 h and FPG stained. All categories of chromatid-type aberrations were scored in G 2 and S phase cells. As expected, mitotic delay in the presence of caffeine, (measured by a shift in the portion of the fraction of differentially stained metaphases (FDM) curve and a reduced fall in the mitotic index) was largely cancelled, but there was a negligible increase in chromatid-aberration frequency (all categories), only achieving significance if the consistency of the whole 7-h sampling period was considered. Caffeine had no effect on the frequencies of light/dark chromatid involvement, nor in the completeness of chromatid interchanges. We conclude that the enhanced breakage frequency often observed with post-irradiation caffeine treatment is not necessarily causally related to the cancellation of delay.

A control theory approach to the stability and transient analysis of the filtered-x LMS adaptive notch filter

A method is presented for analyzing the stability and transient response of the filtered-x LMS adaptive notch filter by formulating the problem in the complex weight domain and applying standard control theory. Examples are given for pure delay and second-order low-pass cancellation path transfer functions. The method is also extended to the multichannel case, where the eigenvalues of the equivalent open-loop transfer function matrix characterize the behavior. >