On the Coupling of Power-Related and Inner Inverter Control Loops of Grid-Forming Converter Systems

In the last decade, different control concepts for the synchronisation of voltage-controlled power converters have been proposed in order to form converter-based power systems. The interoperability of these grid-forming power controls is often analysed based on reduced-order models covering only the slow controls or modes. In this article, the coupling of the outer, power-related and inner, inverter output-related control of multiple grid-forming power converter systems is analysed, based on a minimal working example. The elementary study cases each consist of a different grid-forming converter coupled with an external (and passive) grid. Here, the investigated stability problems are already manifested in the simplest possible setup. The analysis of these coupling effects is performed by modelling the system in impedance-based, state-space and phase portrait-based frameworks. In particular, small coupling impedances, like short transmission lines or small short circuit impedances, can be challenging for the controller stability of grid-forming converters while the inner controls can even enhance this issue. The impact of this phenomenon and the participating subsystems are identified in this work. Thus, recommendations concerning modelling techniques and their legitimate assumptions are given. Laboratory experiments validate the performed analysis by indicating a close correlation between analytical models and experimental results. CCB

Breakdown and recovery of thin gate oxides

Breakdown events are studied in varying test set-ups with a high time resolution. Often a partial recovery from breakdown is observed\ud within a few ms. Parameters such as device area, stress conditions and parasitic elements prohibit the recovery if they result in a high system impedance. The results suggest the existence of a highly conductive path that can be annihilated during breakdown

Error-rate in Viterbi decoding of a duobinary signal in presence of noise and distortions: theory and simulation

The Viterbi algorithm, presented in 1967, allows a maximum likelihood de- coding of partial response codes. This study focuses on the duobinary code which is the first member of this family and has been specified for the digital part of television systems recommended by International Organizations. Up to now the error-rate, which is the main criterion of the performance, has been evaluated by simulation. Although there exist the- oretical bounds, these bounds are not satisfactory for a channel such as broadcasting (by terrestrial transmitters, cable networks or satellite) which is strongly impaired by noise, and linear and non-linear distortions. Analytical methods, verified by simulation, are presented here in order to evaluate the theoretical and exact values of the error-rate, in the form of series of numerical integrations, for a transmission in baseband or in radio-frequency with quadriphase modulation (or AM/VSB for cable networks) and coherent demodulation, in presence of noise and several distortions. This methodology can be later extended to other partial response codes, to convolutional codes and their concatenations

Electrochemical synthesis of new electroactive polymers from dithienylene-vinylene derivatives

peer reviewedHighly conjugated thiophene derivatives, based on thienylene-vinylene and thieneylene-vinylene-phenylene units, have been synthesized in order to examine: (i) the effect of such regular conjugated monomer structures on the polymerization; (ii) the optical and electrochemical properties of the corresponding conjugated polymers. The all-trans monomers have been prepared by a Wittig reaction and the polymers have then been synthesized electrochemically. The polymers are electrochromic and can be reversibly doped both oxidatively and reductively. Their electrochemical behavior and optical properties have been analysed on the basis of quantum-chemical calculations

Electrodeposition, characterization and corrosion behaviour of tin-20 wt.% zinc coatings electroplated from a non-cyanide alkaline bath

Tin-zinc alloy electroplated coatings are recognized as a potential alternative to toxic cadmium as corrosion resistant deposits because they combine the barrier protection of tin with the cathodic protection afforded by zinc. The coatings containing 20 wt.% zinc, balance tin, offer excellent corrosion protection for steel and do not form gross voluminous white corrosion products like pure zinc or high zinc alloy deposits. In this study, the effects of variables of the process (i.e. cathodic current density, pH and temperature) on deposit composition have been evaluated using a Hull cell to obtain 20 wt.% zinc alloy coatings. The tin-20 wt.% zinc deposits, produced with electroplating optimized conditions, were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), X-ray fluorescence spectrometry (XRF) and glow discharge optical emission spectrometry (GDOES). On the other hand, the corrosion behaviour of tin-zinc alloy electroplated coatings on steel has been investigated using electrochemical methods in a 3 wt.% NaCl solution and the salt spray test. The performance of the deposits was compared with cadmium and zinc-nickel electrodeposited coatings. The results show that the corrosion resistance of tin-20 wt.% zinc alloy coating is superior to that of cadmium and zinc-12 wt.% nickel coatings. Finally, sliding friction tests were conducted

Intermittent Brugada syndrome in an anorexic adolescent girl

AbstractWe report an anorexic adolescent girl with an intermittent Brugada syndrome. A 14-year-old anorexic girl with a body mass index (BMI) of 13.15kg/m2 was admitted in the acute state of the disease with an ST elevation in V1 and V2, suggestive of Brugada syndrome. After 1 month of re-feeding, a control electrograph (ECG) was normal, but after an 8-month follow-up control with a nearly normal BMI, the ECG was again suggestive of Brugada syndrome. A genetic analysis of the gene SNC5A established a genetic change (p Leu 1582 pro), which provides the final explanation for the Brugada syndrome. Every rhythm problem in the acute state or during the re-feeding procedure deserves a strict follow-up to distinguish iatrogenic from heritable rhythm problems.<Learning objective: (i) We report the first case of a patient with anorexia nervosa with an intermittent Brugada syndrome. (ii) Moderate hypothermia can decrease the depolarization of pacemaker cells and cause ST-segment changes. (iii) Every rhythm problem in the acute state or during the re-feeding procedure deserves a strict follow-up to distinguish iatrogenic from heritable rhythm problems. (iv) A genetic analysis can make the distinction and is necessary to give advice for the future lifestyle of the patient.