Step Change Detection for Improved ROCOF Evaluation of Power System Waveforms

In the analysis of power grid waveforms, the presence of amplitude or phase steps can disrupt the estimation of frequency and rate-of-change-of-frequency (ROCOF). Standard methods based on phasor-models fail in the extraction of signal parameters during these signal dynamics, often yielding large frequency and ROCOF deviations. To address this challenge, we propose a technique that approximates components of the signal (e.g., amplitude and frequency variations) using dictionaries based on parameterized models of common signal dynamics. Distinct from a previous iteration of this method developed by the authors, the proposed technique allows for the identification of multiple steps in a window, as well as the presence of interfering tones. The method is shown to improve signal reconstruction when applied to real-world waveforms, as compared to standard static and dynamic phasor-based algorithms.

Step detection in power system waveforms for improved RoCoF and frequency estimation

Asja Derviskadic, Guglielmo Frigo, Alexandra Cameron Karpilow, Mario Paolone

The evaluation of the signal frequency and Rate of Change of Frequency (RoCoF) from voltage or current waveforms is used for critical grid control, monitoring and protection applications. However, when step changes in the amplitude or phase of the signal occur, conventional frequency and RoCoF estimation methods, typically based on phasor models, are highly unreliable and can yield large frequency errors. To address this issue, this paper proposes a technique that uses dictionaries based on common signal dynamic models to identify and track amplitude and/or phase steps in AC signals. Additional signal dynamics including amplitude modulations, frequency ramps and harmonic tones are also characterized. Distinct from a previous iteration of this method developed by the authors, the proposed Step Change Detection (SCD) technique separates the envelope and angle of the signal's analytic form for independent analysis of these components. For numerical validation the method is applied to synthetically generated signals with challenging combinations of signal dynamics. The technique is shown to greatly improve frequency and RoCoF approximations as compared to state-of-the-art phasor estimation methods.

ELSEVIER SCIENCE SA2022

Nanopore sensing of single molecules application to RNAP-DNA complexes, fabrication of graphene-nanopore devices and translocation algorithm analysis

Camille Alice Raillon

Nanopore sensing is a single-molecule technique that allows to probe the nano-bio-world with accuracy. It is a non-invasive technique, which means that the molecule of interest does not need to be labeled to be detected by the nanopore. Most of the studies done with nanopores use electrophoresis. With an electric field applied across the nanopore, charged molecules move through this tiny hole. When a molecule passes through the nanopore it creates a dip in current, called current blockage, because it partially blocks the ions from going through and so it increases the nanopore resistance. This phenomenon is observed using a refined ammeter that detects changes in current in the range of pA. At the Laboratory of Nanoscale Biology (LBEN), we are interested in very small biological units, and this thesis is focused on the RNA polymerase, the enzyme that catalyzes the transcription reaction. Transcription is the first step in gene expression where DNA is copied into RNA. It is extensively studied at the bulk level especially the regulation mechanism, which in cancerous cells is impaired. We were interested in studying this enzyme at the single-molecule level for its functional as well as molecular motor properties. This work was done in close collaboration with Pascal Cousin at the Center for Integrative Genomics (CIG) in the group of Nouria Hernandez who helped to design the protein-DNA complexes and analyze the data. With nanopore sensing we were able to observe RNA polymerase-DNA complexes translocate through nanopores and capable to distinguish between individual complexes and bare RNA polymerase. We were also able to observe orientation of RNA polymerase in the nanopore whether flow or electric field predominates. The complexity of the signals from the protein-DNA complexes experiment motivated the development of a level detection software. This software was written in collaboration with Pierre Granjon from GIPSA-lab in Grenoble who had the expertise on a change detection method called the CUSUM algorithm. Our software was designed to analyze in details current blockages in nanopore signals with very little prior knowledge on the signal. With this work one can separate events according to their number of levels and study those sub-populations separately. This method also allows a global statistical view of all levels by plotting what we call a level histogram. We demonstrate that with such a technique one can identify populations that cannot be seen otherwise. As the theoretical literature has shown, it should be possible to sequence a ssDNA with a nanopore using transverse electronics for tunneling current measurement. In this thesis, we will discuss the fabrication work done on the first generation of graphene-nanopore devices and how we overcame the fabrication issues to produce reliable devices.

EPFL2012

Cryogenic single chip electron spin resonance detectors

Gabriele Gualco

Methods based on the electron spin resonance (ESR) phenomenon are used to study paramagnetic systems at temperatures that ranges from 1000 to below 1 K. Commercially available spectrometers achieve spin sensitivities in the order of 10^(10) spins/¿Hz at room temperature on sample with volumes in the order of few µl. This results can be improved by cooling the system at cryogenic temperatures, where the larger magnetization of paramagnetic samples cause the detected signal to increase. Furthermore operation at high field (frequency) turns as well in an improved spin sensitivity. For what it concern the spin sensitivity operation at cryogenic temperature and high frequency are thus beneficial. In 2008 the group of Dr. G. Boero proposed a novel detection method based on the integration of all the element responsible for the sensitivity on a single silicon chip. The methodology allowed to study sample with nanoliter scale volume with spin sensitivity that were at least 2 orders of magnitude better than the best commercial spectrometer. The proposed method has performance that are comparable with the one obtained on similar scales with micro-resonator based spectroscopy tool. During this thesis I have investigated the possibility of extending the use of the detection method from frequency that goes from 20 to 200 GHz and temperatures that range from 77 to 4 K. In this frame several domains were touched. First of all the design of CMOS silicon oscillators operating at frequency which are closed to the most modern technology frequency limit. The lack of model valid for the target frequencies and the needs of limiting the power consumption for matching the limited cooling power of cryogenic systems, made the subject a challenging and interesting research topic itself. The study produces a remarkable result of a system operating at about 170 GHz with a power consumption of about 3 mW at room temperature and about 1.5 mW at 4 K. With the realized devices the first measurements of integrated silicon CMOS LC oscillators at temperature below 77 K were performed. From this measurements we could confirm the presence of expected effect, such as minimum power consumption reduction and oscillator frequency increase. In addition to that, by measuring the frequency-bias characteristic, it's been noticed a succession of smooth region and sharp transitions. This jumps are tentatively attributed to the random telegraph signal (RTS) effect that is supposed to be the main responsible for the flicker noise in sub-micrometer MOS devices. Since the impact of RTS on the performance of highly scaled transistor performance is expected to grow with the technology scale down, measurement methods based on LC oscillator, that shows better sensitivity if compared with nowadays employed methods, might allow to better understand the mechanism governing the effect and to develop technological strategy for lowering the impact on the future CMOS technology node. The realized devices have finally demonstrated ESR performances that are comparable with the most recent publication done with miniaturized resonators on mass-limited samples. In fact sensitivity of about 10^(7) spins/¿Hz at 50 GHz and 300 K and of about 10^(6) spins/¿Hz at 28 GHz and 4 K, at least 3 orders of magnitude better then commercially available state of the art devices, have been proven.