A Novel PWM/PFM Control Technique for Transient Improvement and High Efficiency Over a Wide Load Range in Buck DC-DC Converter

2018 ◽  
Author(s):  
Kai Luo ◽  
Han Wang ◽  
Chao Gou ◽  
Kewu Peng ◽  
Feng Yang ◽  
...  
Keyword(s):  
High Efficiency ◽  
Control Technique ◽  
Load Range ◽  
Transient Improvement

scholarly journals ZVS Auxiliary Circuit for a 10 kW Unregulated LLC Full-Bridge Operating at Resonant Frequency for Aircraft Application

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1850 ◽  
Author(s):  
Yann E. Bouvier ◽  
Diego Serrano ◽  
Uroš Borović ◽  
Gonzalo Moreno ◽  
Miroslav Vasić ◽  
...  
Keyword(s):  
Resonant Frequency ◽  
Power Density ◽  
High Efficiency ◽  
Harmonic Approximation ◽  
Maximum Efficiency ◽  
Voltage Gain ◽  
Load Range ◽  
Transition Analysis ◽  
Aircraft Application ◽  
Auxiliary Circuit

In modern aircraft designs, following the More Electrical Aircraft (MEA) philosophy, there is a growing need for new high-power converters. In this context, innovative solutions to provide high efficiency and power density are required. This paper proposes an unregulated LLC full-bridge operating at resonant frequency to obtain a constant gain at all loads. The first harmonic approximation (FHA) model is not accurate enough to estimate the voltage gain in converters with high parasitic resistance. A modified FHA model is proposed for voltage gain analysis, and time-based models are used to calculate the instantaneous current required for the ZVS transition analysis. A method using charge instead of current is proposed and used for this ZVS analysis. Using this method, an auxiliary circuit is proposed to achieve complete ZVS within the whole load range, avoiding a gapped transformer design and increasing the efficiency and power density. A 28 Vdc output voltage prototype, with 10 kW peak output power, has been developed to validate the theoretical analysis and the proposed auxiliary circuit. The maximum efficiency (96.3%) is achieved at the nominal power of 5 kW.

Indentation Crack Initiation and Ductile to Brittle Transition Behavior of Fused Silica

2013 ◽  
Vol 797 ◽  
pp. 667-672 ◽  
Author(s):  
Peng Yao ◽  
Wei Wang ◽  
Chuan Zhen Huang ◽  
Jun Wang ◽  
Hong Tao Zhu ◽  
...  
Keyword(s):  
Penetration Depth ◽  
High Efficiency ◽  
Fused Silica ◽  
Load Range ◽  
Brittle Transition ◽  
Ductile Mode ◽  
Indentation Crack ◽  
Ultra Precision ◽  
Ductile To Brittle Transition ◽  
Brittle Mode

To provide a fundamental knowledge for the high efficiency grinding and ultra-precision grinding of fused silica, ductile mode and brittle mode material removal mechanisms were investigated by conducting micro/nanoindentation experiments in the range of 4.9 mN - 1960 mN. Before observing cracks and determining the ductile to brittle transition penetration depth, the samples were etched with hydrofluoric acid to expose cracks. The typical damage morphology of fused silica was discussed by observing the surface and cross-section of indentations, and the depth of SSD was found to be determined by the cone cracks or borderline cracks in the different load range. The ductile to brittle transition penetration depth of fused silica under Vickers indentation was 180 nm.

Design and Implementation of Z-Source Inverter by Simple Boost Control Technique for Laboratory Scale Micro-Hydro Power Plant Application

2021 ◽  
Vol 13 (2) ◽  
pp. 62-70
Author(s):  
Rizki Mendung Ariefianto ◽  
Rizky Ajie Aprilianto ◽  
Heri Suryoatmojo ◽  
Suwito Suwito
Keyword(s):  
Power Plant ◽  
High Efficiency ◽  
Electrical Power ◽  
Harmonic Distortion ◽  
Laboratory Scale ◽  
Control Technique ◽  
Induction Generator ◽  
Duty Ratio ◽  
Hydro Power ◽  
Boost Control

In a power plant such as micro-hydropower (MHP), an induction generator (IG) is usually employed to produce electrical power. Therefore, an inverter is needed to deliver it with high efficiency. Z-source inverter (ZSI) has been introduced as a topology with many advantages over conventional inverters. This research aims to investigate the performance of ZSI based simple boost control (SBC) in laboratory-scale MHP systems using a rewinding induction generator. This research has been conducted both from simulations and experiments. Based on the result, the waveform characteristic and value of ZSI are close to the desired design. A shoot-through duty ratio of 17% can reach 60 Vrms output voltage, and this condition has a conversion ratio of about 2.05 times. Also, SBC can significantly reduce the Total Harmonic Distortion (THD). ZSI efficiency has a value of 84.78% at 50% of rating load 100 W and an average value of 80%. Compared to the previous study, the proposed design has more economical with the same component for the higher rating power. Moreover, it has a smoother and entire output waveform of the voltage.

scholarly journals An Introduction Into the Clearance Management of Ansaldo GT36 From Development to Validation

2018 ◽  
Author(s):  
S. Boeller ◽  
B. Feuillard ◽  
G. Filkorn ◽  
S. Olmes ◽  
F. Prou ◽  
...  
Keyword(s):  
Gas Turbine ◽  
High Efficiency ◽  
Evaluation Process ◽  
3D Models ◽  
Operating Conditions ◽  
Active Management ◽  
Test Plant ◽  
Pinch Point ◽  
Load Range ◽  
Clearance Prediction

The optimization and evaluation of blading clearance is important for gas turbine efficiency and performance. The Ansaldo GT36 gas turbine offers high efficiency together with outstanding flexibility across a large load range. Active management of engine clearances during the complete development process followed by a thorough validation on the Ansaldo test plant facility in Birr, Switzerland enables the GT to attain ambitious clearance targets. The clearance at baseload must be minimized but is limited by the pinch point clearance during cold, warm and hot start-ups — including normal and fast ramp-up and/or shutdown. Therefore transient analysis is necessary for covering the different operating conditions. A well-established process of 2d finite element modelling of the whole engine model (WEM) comprised of axis-symmetric and plane stress elements was used during the design process from concept to detailed design to optimize the clearances. It delivers the transient stator and rotor deformation and together with the compressor and turbine airfoil deformation based on 3D models the basic clearance evaluation process is defined. The GT engine design was significantly influenced, starting with a simplified version of the WEM for identification of the most promising variants. Subsequently a detailed WEM was developed which is fully validated against measurements on the test engine. Different 3D effects are considered separately at identified critical transient conditions and overlaid on the 2d clearances which lead to the final optimized clearances. In addition to this, limitations from each step of the manufacturing process were identified and improved to reduce tolerances and uncertainties to their minimum. The results of the calculation and clearance prediction process are compared against clearance measurements during all kinds of GT operation and cooldown. Passive clearance indicators showing the remaining gap till rubbing would occur and rub marks, in areas that tolerate it, further validate the clearances and clearance prediction process.

scholarly journals Study of Energy Compensation Techniques in Photovoltaic Solar Systems with the Use of Supercapacitors in Low-Voltage Networks

Energies ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3755 ◽  
Author(s):  
Luis Gerardo González ◽  
Rommel Chacon ◽  
Bernardo Delgado ◽  
Dario Benavides ◽  
Juan Espinoza
Keyword(s):  
Energy Storage ◽  
High Efficiency ◽  
Low Voltage ◽  
Storage System ◽  
Weather Conditions ◽  
Rate Of Change ◽  
Photovoltaic System ◽  
Control Technique ◽  
Electrical Networks ◽  
Solar Systems

The power generated by photovoltaic solar systems is exposed to high variability of irradiance mainly due to weather conditions, which cause instability in the electrical networks connected to these systems. This study shows the typical behavior of solar irradiance in an Andean city, which presents considerable variations that can reach up to 63% of the nominal power of the photovoltaic system, at time intervals in the order of seconds. The study covers the application of 3 techniques to reduce power fluctuations at the point of common coupling (PCC), with the incorporation of energy storage systems, under the same irradiance conditions. Supercapacitors were used as the storage system, which were selected for their high efficiency and useful life. A state of charge control is also applied by means of a hysteresis band. The three algorithms studied show similar behaviors; however, the ramp control technique has the best performance. The storage system was dimensioned based on the photovoltaic system’s nominal power and the desired rate of change in the PCC, whose capacity can be estimated from Pnom/12 [kWh] and a maximum power that can reach up to 0.63 Pnom. The study determines that based on the storage capacity and the irradiance characteristics under study, the storage system could use at least 5.76 daily charge/discharge cycles. In the study, it is possible to reduce the rate of change of the photovoltaic energy injected into the PCC about 6.66 times with the use of the proposed energy storage system.

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