4 research outputs found
A sliding mode based controller for no inertia islanded microgrids
No full textThe papers presents a new concept for controlling voltage and frequency in islanded microgrids composed by a Battery Energy Storage System (BESS) and Photo-Voltaic (PV) Units. The proposed approach is totally decentralized as each source is equipped with a purely local controller and no communication infrastructure is needed. Moreover, a centralized secondary control is not required as the developed local controllers are able to nullify both frequency and voltage errors. Finally, the physical constraints related to BESS power and State Of Charge (SOC) limits are accounted and some theoretical hints are provided to justify why the frequency can be used as a triggering signal for the controllers to switch among the different operation modes even in absence of synchronous machines directly connected to the grid
Performance evaluation of single-stage photovoltaic inverters under soiling conditions
No full textFly ash soiling effects are an air pollution consequence, especially during the heating season, and have considerable influence on the ability of urban photovoltaic (PV) systems to operate as an electricity supply grid. In this paper, an experimental study of soiling influence on PV systems with single-stage inverters was conducted on the hybrid micro-grid example. PV panel field measurements showed that soiling induces not only well-known maximum power point (MPP) tracking problem, but also reduces available power up to 30 %. Laboratory comprehensive tests with PV panels measured and emulated characteristics showed that, due to soiling, grid forming single-stage inverters operate with stability operation problems that can lead to energy production cessation.A reliable MPP estimation providing PV system with sufficient power reserve is necessary for hybrid micro-grid uninterrupted operation. In case of MPP tracking, it is necessary to establish additional limitations for the DC voltage to keep grid inverter functionality
NADPH oxidase and redox status in amygdala, hippocampus and cortex of male Wistar rats in an animal model of post-traumatic stress disorder
No full textPost-traumatic stress disorder (PTSD) is a highly prevalent and impairing disorder. Oxidative stress is implicated in its pathogenesis. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is an important source of free radicals. The aim of the study was to assess oxidative stress parameters, activities of respiratory chain enzymes, and the expression of NADPH oxidase subunits (gp91phox, p22phox, and p67phox) in the single prolonged stress (SPS) animal model of PTSD. Twenty-four (12 controls; 12 subjected to SPS), 9-week-old, male Wistar rats were used. SPS included physical restraint, forced swimming, and ether exposure. The rats were euthanized seven days later. Cortex, hippocampus, amygdala, and thalamus were dissected. Malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), Complex I, and cytochrome C oxidase were measured using spectrophotometric methods, while the expression of NADPH oxidase subunits was determined by Western blot. Increased MDA and decreased GSH concentrations were found in the amygdala and hippocampus of the SPS rats. SOD activity was decreased in amygdala and GPx was decreased in hippocampus. Increased expression of the NADPH oxidase subunits was seen in amygdala, while mitochondrial respiratory chain enzyme expression was unchanged both in amygdala and hippocampus. In the cortex concentrations of MDA and GSH were unchanged despite increased Complex I and decreased GPx, while in the thalamus no change of any parameter was noticed. We conclude that oxidative stress is present in hippocampus and amygdala seven days after the SPS procedure. NADPH oxidase seems to be a main source of free radicals in the amygdala.</p
