Galvanical isolated microinverter with GaN transistors for photovoltaic modules

A microinverter with GaN transistors is presented in this work. It consists of two stages: a DC-DC-stage with HF galvanic isolation in combination with an inverter stage. High efficiency above 97.5 % is reached in all stages. The weight of the demonstrator developed is 492 gr at 675 cm³

Übergeordnetes Regelungskonzept für PV-Heimspeichersysteme und deren Anforderungen an die Leistungselektronik

PV-Heimspeichersysteme ermöglichen den Eigenverbrauch einer Photovoltaikanlage zu erhöhen und können gleichzeitig bei geeigneter Betriebsweise die Stromnetze entlasten. Die Speichersysteme können an verschiedenen Stellen in das Hausnetz bzw. in eine Photovoltaikanlage eingebunden werden. So kann ein Anschluss direkt an das AC-Netz, auf der PV-Generator-Seite oder am Zwischenkreis eines Solar-Wechselrichters erfolgen. Im vorliegenden Fall werden für ein am Zwischenkreis gekoppeltes System übergeordnete Regelungskonzepte betrachtet und insbesondere auf deren Auswirkung auf die Anforderungen an die Leistungselektronik eingegangen

Partial-Load Optimization of a High-Voltage Residential Battery Converter with Silicon Carbide MOSFETs

The specific importance of high partial-load efficiency during discharge for battery converters in residential installations is discussed. Methods to optimize the efficiency of the converter particularly under light-load conditions are presented and scientifically analyzed. A bidirectional, multi-leg half-bridge converter was designed in order to validate the theoretical findings. The key insights and the measurement results of the implemented optimizations are presented

Modulare Leistungselektronik für Heimspeichersysteme

Die Anforderungen an Wechselrichter für Photovoltaik- (PV), wie auch für Batterie-anwendungen, sind in den letzten Jahren immer anspruchsvoller geworden. Heute übliche Systeme müssen neben einem hohen Umwandlungswirkungsgrad, einer ausreichenden Zuverlässigkeit und günstigen Herstellungskosten zunehmend auch Netzdienstleistungen zur Verfügung stellen können und flexibel einsetzbar sein. Daher wird in der vorliegenden Arbeit ein konsequent modularer Aufbau eines DC-gekoppelten Heimspeichersystems realisiert, um eine flexible System-konfiguration zu ermöglichen. Um die Systemkosten zu minimieren sowie eine kompakte Bauweise zu ermöglichen, wurden schnelltaktende Siliziumkarbid (SiC)- und Galliumnitrid (GaN)-Transistoren eingesetzt und eine entsprechende kostenoptimierte Auslegung der induktiven Bauelemente untersucht

Interpopulation Comparisons of Antipredator Defense Behavior of the Thorn-Tailed Rayadito (Aphrastura spinicauda)

The high impact of predators on breeding success has favored the evolution of diverse behavioral strategies that enhance both individual survivorship and reproductive success. Self- and nest-defense against predators are inter-related behaviors that vary according to life history traits and the risks involved in defense. In addition, interpopulation differences in the composition of predator guilds, and hence predation pressures, may result in geographic variation in antipredator defense strategies. It is generally accepted that the absence of predators could drive the loss of antipredator behavior. However, it is unclear how species respond if one type of predator (e.g., a specialized nest predator) is absent but others are present. The multipredator hypothesis suggests that the absence of only a few predators is not sufficient to drive a change or loss of antipredator behavior in a species. We examined interpopulation variation in defense behavior in the thorn-tailed rayadito (Aphrastura spinicauda), a suboscine bird inhabiting a wide latitudinal range in southern South America. In populations where nest predators were either present or absent, we examined the responses of rayaditos to an adult predator (an owl) and to a nest predator (a marsupial). Owl-defense behavior involved more intense and longer responses than marsupial-defense. This suggests that adult rayaditos may allocate more energy to defend themselves than their young. However, because the presence of adult predators near the nest also prevents parents from feeding the nestlings, owl-defense may simultaneously represent a form of nest-defense. No differences in marsupial-defense were found among the three sampled populations, despite the absence of native mammalian nest predators in one population. The lack of variation in nest-defense behavior provides some support for the multipredator hypothesis, although the high interpopulation gene flow in this species could also contribute to this behavior’s maintenance.Fil: Ippi, Silvina Graciela. Universidad de Chile; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: van Dongen, Wouter F. D.. Universidad de Chile; Chile. University of Veterinary Medicine Vienna; AustriaFil: Lazzoni, Ilenia. Universidad de Chile; ChileFil: Venegas, Cristobal I.. Universidad de Chile; ChileFil: Vásquez, Rodrigo A.. Universidad de Chile; Chil

Independent hypothalamic circuits for social and predator fear

The neural circuits mediating fear to naturalistic threats are poorly understood. We found that functionally independent populations of neurons in the ventromedial hypothalamus (VMH), a region that has been implicated in feeding, sex and aggression, are essential for predator and social fear in mice. Our results establish a critical role for VMH in fear and have implications for selective intervention in pathological fear in humans