Search results for "Converter"
showing 10 items of 275 documents
Control of Power Converters with Hybrid Affine Models and Pulse-Width Modulated Inputs
2021
In this paper, hybrid dynamical systems theory is applied to the analysis and control of switched converters with Pulse-Width Modulated (PWM) inputs. The system is described by a state-space model with continuous flows and discrete jumps, without averaged equations. The modulation effects are captured in full without using time-dependent signals, by enlarging the state vector to include the PWM waveform generation process. Furthermore, the sample-and-hold mechanism associated with the sampling frequency is also taken into account with this approach. A control law is proposed based on a Lyapunov function candidate. Furthermore, convergence sets and the steady state jitter, inherent to PWM-ba…
Partial Discharge Measurements under DC Voltages Containing Harmonics Produced by Power Electronic Devices
2018
Partial Discharge (PD) monitoring is one of the main diagnostic instrument to evaluate the reliability of modern electrical transmission and distribution systems. The widespread use of High voltage dc (HVDC) connections increase the demand of voltage source converters (VSCs) which, as a consequence, has brought about new challenges in the field of partial discharge measurements. In fact, the output voltage waveforms generated by AC/DC modular multilevel converters (MMCs) are affected by a significant harmonic content which influences the Partial Discharges (PDs) activity. For this reason, previous research mainly investigated the PD phenomenon on the AC side of the converter. The aim of the…
Design and experimental validation of a high voltage ratio DC/DC converter for proton exchange membrane electrolyzer applications
2019
Abstract This paper deals with hydrogen production via water electrolysis, which is considered the most attractive and promising solution. Specifically, the use of renewable energy sources, such as wind electric power generators, is hypothesized for supplying the electrolyzer, aiming to strongly reduce the environmental impact. In particular, micro-wind energy conversion systems (μWECSs) are attractive for their low cost and easy installation. In order to interface the μWECS and the electrolyzer, suitable power conditioning systems such as step-down DC-DC converters are mandatory. However, due to the requested high conversion ratio between the DC bus grid, i.e. the output of a three-phase d…
Characterization of Non-linear Inductors Including Thermal Effects for Power Applications
2018
This paper is focused on the behaviour of non-linear inductors employed in DC/DC switching converters considering the effects due to variations of both current and temperature. The characterization of the inductors is performed by a buck converter operated to stimulate the inductor under test by a constant current with superimposed a large signal. The measurements are carried out at several inductor’s temperature values. Data are automatically collected by a novel virtual instrument developed by the authors in LabVIEW® environment aiming to obtain a polynomial based analytical model. The deep knowledge of the inductor model allows its design to be optimized improving the power density of th…
Non-linear inductor modelling for a DC/DC buck converter
2017
The paper is focused on the modelling of an inductor to exploit its non-linear behaviour in the roll-off region when it is employed in a DC/DC converter. The model is set up on the basis of experimental data measured in operating conditions, which are fitted to a polynomial curve describing the inductance variations. The analysis of the buck converter, performed by including the proposed model, is validated by experimental tests.
A Test Circuit for GaN HEMTs Dynamic Ron Characterization in Power Electronics Applications
2019
Wide bandgap devices such as GaN HEMTs are a promising technology in the field of Power Electronics. Due to the physical properties of the Gallium nitride and the device design, they can outperform their Silicon counterparts for the design of highly efficient power switching converters. However, its design should face certain effects that can diminish its performance. One of such effect is the degradation mechanism known as dynamic onresistance (dynamic RON,), being its mitigation one of the main objectives in the design of the device. In this paper, a circuit is proposed for assessing if this effect is present in GaN transistors in power electronics applications. The circuit allows testing…
Power losses comparison between Silicon Carbide and Silicon devices for an isolated DC-DC converter
2021
In recent years, new efficient power devices have been implemented. Silicon Carbide has replaced silicon as regards the production and the utilization of many devices, such as MOSFETs, diodes, IGBTs and many others. SiC devices are characterized by a low reverse recovery charge, high carrier saturation velocity, by which it is possible to work at high frequency, and high breakdown voltage. Thanks to the great thermal conductivity and the wide bandgap, these devices can operate at high temperature and reach high voltages and currents. What is important to stress is the fact that power losses in SiC devices are lower than the silicon ones. These are the reasons why these devices are utilized …
Efficiency comparison between SiC- and Si-based active neutral-point clamped converters
2015
This paper presents an efficiency comparison between silicon-carbide technology and silicon technology. In order to achieve this, the efficiency of an active neutral-point clamped converter built up with silicon carbide power-devices is compared with the efficiency of an active neutral-point clamped converter built up with silicon power-devices, under a particular operating mode and a particular selection of devices. Firstly, overall losses of both converters are estimated. Then, experimental tests are carried out to measure their overall losses and efficiency. Finally, experimental results are compared with the estimations to support the analysis. The efficiency of the SiC converter is hig…
Evaluation of Gallium Nitride Transistors in Electronic Power Conditioners for TWTAs
2015
The aim of this paper is to evaluate the benefits of replacing Si Mosfets transistors with enhancement mode GaN transistors in a Half-Bridge Zero Voltage and Zero Current Switching Power Switching Converter (ZVZCPS). This converter is usually used as power supply of the travelling-wave tube amplifiers (TWTAs) in aerospace applications. In this paper, firstly the converter is theoretically analyzed, obtaining its operation, losses and efficiency equations, these equations are used to obtain optimizations maps based on the main system parameters. In this way, the ideal design parameters can be visually obtained. These optimization maps are the key to quantify the potential benefits of GaN tra…
Negative capacitance caused by electron injection through interfacial states in organic light-emitting diodes
2006
The negative capacitance frequently observed at low frequencies in organic light-emitting diodes (LEDs) is explained as a signature of sequential electron injection at the organic/metal interface first to states in the bandgap in the dipole layer and then to bulk states. The negative capacitance occurs when the interfacial states depart from equilibrium with the metal Fermi level due to an increasing rate of hopping to the bulk states. A simple kinetic model compares well with the experimental results and provides a new tool to investigate interfacial properties for improving the performance of organic LEDs.