LCL-filters are used to mitigate the harmonic current content in grid converters. The LCL-filter resonance must be damped in order to avoid stability problems in the current control. Active damping avoids resistors at the expense of increased control complexity. Large grid impedance variations can challenge the LCL-filter stability. Active damping by using a notch filter on the reference voltage for the modulator is simple to implement and does not require additional sensors. With the notch frequency tuned for the resonant frequency the voltage reference does not contain any component susceptible of exciting the LCL-filter. However, the notch filter tuning requires considerable design effort and the variations in the resonance frequency limit the LCL-filter robustness. This paper proposes a simple tuning procedure for the notch filter that results in proper robustness. In order to cope with the grid inductance variations it is proposed to estimate the resonance frequency by means of Fourier analysis. The Goertzel algorithm, instead of the FFT, is used to reduce the calculation and memory requirements. Thus, the proposed self-commissioning notch filter results robust and consumes little computational resources. Finally, the analysis is validated with both simulation and experiments.

/pdf/self-commissioning-notch-filter-for-active-damping-in-three-3t4cp2x0gt.pdf

Self-commissioning notch filter for active damping in three phase LCL-filter based grid converters

Distributed fiber-optic vibration sensors receive extensive investigation and play a significant role in the sensor panorama. Optical parameters such as light intensity, phase, polarization state, or light frequency will change when external vibration is applied on the sensing fiber. In this paper, various technologies of distributed fiber-optic vibration sensing are reviewed, from interferometric sensing technology, such as Sagnac, Mach-Zehnder, and Michelson, to backscattering-based sensing technology, such as phase-sensitive optical time domain reflectometer, polarization-optical time domain reflectometer, optical frequency domain reflectometer, as well as some combinations of interferometric and backscattering-based techniques. Their operation principles are presented and recent research efforts are also included. Finally, the applications of distributed fiber-optic vibration sensors are summarized, which mainly include structural health monitoring and perimeter security, etc. Overall, distributed fiber-optic vibration sensors possess the advantages of large-scale monitoring, good concealment, excellent flexibility, and immunity to electromagnetic interference, and thus show considerable potential for a variety of practical applications.

https://www.mdpi.com/1424-8220/16/8/1164/pdf

Distributed Fiber-Optic Sensors for Vibration Detection

From the Publisher: 
This is undoubtedly the most accessible book on digital signal processing (DSP) available to the beginner. Using intuitive explanations and well-chosen examples, this book gives you the tools to develop a fundamental understanding of DSP theory. The author covers the essential mathematics by explaining the meaning and significance of the key DSP equations. Comprehensive in scope, and gentle in approach, the book will help you achieve a thorough grasp of the basics and move gradually to more sophisticated DSP concepts and applications.

数字信号处理 = Understanding digital signal processing

The design and preliminary performance results of a fiber-optic (FO) Michelson interferometric hydrophone are described.

Fiber-Optic Hydrophone

The Large Time Frequency Analysis Toolbox (LTFAT) is a modern Octave/Matlab toolbox for time-frequency analysis, synthesis, coefficient manipulation and visualization. It’s purpose is to serve as a tool for achieving new scientific developments as well as an educational tool. The present paper introduces main features of the second major release of the toolbox which includes: generalizations of the Gabor transform, the wavelets module, the frames framework and the real-time block processing framework.

The Large Time-Frequency Analysis Toolbox 2.0

The article deals with the Goertzel algorithm, used to establish the modulus and phase of harmonic components of a signal. The advantages of the Goertzel approach over the DFT and the FFT in cases of a few harmonics of interest are highlighted, with the article providing deeper and more accurate analysis than can be found in the literature, including the memory complexity. But the main emphasis is placed on the generalization of the Goertzel algorithm, which allows us to use it also for frequencies which are not integer multiples of the fundamental frequency. Such an algorithm is derived at the cost of negligibly increasing the computational and memory complexity.

/pdf/goertzel-algorithm-generalized-to-non-integer-multiples-of-e5nlfa5xqa.pdf

Goertzel algorithm generalized to non-integer multiples of fundamental frequency

A sensing system utilizing a standard optical fiber as a distributed sensor for the detection and localization of mechanical vibrations is presented. Vibrations can be caused by various external factors, like moving people, cars, trains, and other objects producing mechanical vibrations that are sensed by a fiber. In our laboratory we have designed a sensing system based on the Φ-OTDR (phase sensitive Optical Time Domain Reflectometry) using an extremely narrow laser and EDFAs.

/pdf/distributed-fiber-optic-sensor-for-detection-and-1udmk1sd01.pdf

Distributed Fiber-Optic Sensor for Detection and Localization of Acoustic Vibrations

Phase-sensitive optical time-domain reectometry (Φ-OTDR) seems to be the most appropriate solution for acoustic vibration along standard optical fiber detection In general the sensing system measures phase changes of the received Rayleigh back-scattered signal in the fiber Since the back-scattered signal intensity is decreased about tens of decibels in comparison to the forward propagating pulse power level, the received signal power level is very low That is why the main limiting parameter of the system is the power level of the back-scattered signal, which limits maximum achievable distance For long reach sensing it is necessary to create high power optical pulses with short time-duration Direct pulse amplification by erbium doped fiber amplifier (EDFA) is an issue because of the pulses low repetition rate We have designed and verified a simple method using a holding beam for amplifying of pulses with low repetition rate by standard telecommunication EDFA booster instead of deployment of an expensive optical shutter A second CW laser with a different wavelength for EDFA stabilization is used in our setup Because a pulse losses its energy during propagation in the fiber and with longer distances by 1st order Raman amplifier (RA) In telecommunications this amplifier is used to compensate for fiber losses The second setup uses remote amplification by remotely pumped erbium doped fiber (EDF) placed after a few tens of kilometers of sensing fiber A pump laser is placed in the transmitter part of the system from where EDF is pumped In this paper, we present an overview of few techniques for Φ-ODTR signals amplification and their verification by measurement

Φ-OTDR signal amplification

The article describe systematically the electromagnetic (EM) side channels sources and electromagnetic field of the microprocessor and is focused on the best way how to measure the near electromagnetic field of microprocessor. It was suggested and realized several electromagnetic probes and it was performed the measurement regarded to the theoretical background on the testbed with cryptographic module (microprocessor) performed the Advanced Encryption Standard (AES). On the measured waveforms of the electromagnetic emission was studied the influence of probe construction namely two parameters wire diameter and number of turns. In following measurement was studied how induced voltage depending on the distance of measuring coil to microprocessor and the last measurement dealt with position of probe and microchip. Streszczenie. W artykule przedstawiono zagadnienie emisji pola elektromagnetycznego przez mikroprocesor i zawartych w nim informacji o stanie układu. Korzystając z platformy mikroprocesorowej, zaimplementowano AES i dokonano pomiarów sondami cewkowymi, badając zależność indukowanego napięcia od parametrów sondy (grubość drutu, ilość zwojów). (Pomiary pola elektromagnetycznego mikroprocesora w bliskiej odległości)

Near electromagnetic field measurement of microprocessor

The paper summarizes the FMT modulation prototype filter design and its efficient implementation on DSP. The optimum design of algorithms for digital signal processors with VLIW architecture is described. Using this new approach it was, for example, possible to optimize compilation from the C language into the assembler of TMS320C6414 digital signal processor for implementation of FMT modulation with prototype FIR filter. The method consists in a closer linkage between the theory of digital signal processing, software tools and hardware.

Petr Sysel

Papers

Goertzel algorithm generalized to non-integer multiples of fundamental frequency

Distributed Fiber-Optic Sensor for Detection and Localization of Acoustic Vibrations

Φ-OTDR signal amplification

Near electromagnetic field measurement of microprocessor

Optimization of FIR filter implementation for FMT on VLIW DSP