scholarly journals Improved Step Load Response of a Dual-Active-Bridge DC–DC Converter

Electronics ◽  
2018 ◽  
Vol 7 (9) ◽  
pp. 185 ◽  
Author(s):  
Yifan Zhang ◽  
Xiaodong Li ◽  
Chuan Sun ◽  
Zhanhong He
Keyword(s):  
Change Process ◽  
Experimental Tests ◽  
Reference Points ◽  
Dc Offset ◽  
Dual Active Bridge ◽  
Load Response ◽  
Load Change ◽  
Instantaneous Current ◽  
Transient Control ◽  
Fixed Reference

This paper proposes a fast load transient control for a bidirectional dual-active-bridge (DAB) DC/DC converter. It is capable of maintaining voltage–time balance during a step load change process so that no overshoot current and DC offset current exist. The transient control has been applied for all possible transition cases and the calculation of intermediate switching angles referring to the fixed reference points is independent from the converter parameters and the instantaneous current. The results have been validated by extended experimental tests.

scholarly journals Blade Tip-timing Technology with Multiple Reference Phases for Online Monitoring of High-speed Blades under Variable-speed Operation

2018 ◽  
Vol 18 (6) ◽  
pp. 243-250 ◽  
Author(s):  
Zhang Ji-wang ◽  
Zhang Lai-bin ◽  
Ding Ke-Qin ◽  
Duan Li-xiang
Keyword(s):  
High Speed ◽  
Online Monitoring ◽  
Rotation Speed ◽  
Experimental Tests ◽  
Reference Points ◽  
Variable Speed ◽  
Rotating Shaft ◽  
Virtual Reference ◽  
Blade Tip ◽  
Multiple Reference

Abstract High-speed blades form core mechanical components in turbomachines. Research concerning online monitoring of operating states of such blades has drawn increased attention in recent years. To this end, various methods have been devised, of which, the blade tip-timing (BTT) technique is considered the most promising. However, the traditional BTT method is only suitable for constant-speed operations. But in practice, the rotational speed of turbomachine blades is constantly changing under the influence of external factors, which lead to unacceptable errors in measurement. To tackle this problem, a new BTT method based on multi-phases is proposed. A plurality of phases was arranged as evenly as possible on the rotating shaft to determine the rotation speed. Meanwhile, the corresponding virtual reference point was determined in accordance with the number of blades between consecutive phases. Based on these reference points, equations to measure displacement due to blade vibrations were deduced. Finally, mathematical modeling, numerical simulation and experimental tests were performed to verify the validity of the proposed method. Results demonstrate that the error in measurement induced when using the proposed method is less than 1.8 %, which is much lower compared to traditional methods utilized under variable-speed operation.

Cheap and accessible method to aid individual photo-identification of grey seals, Halichoerus grypus

2007 ◽  
Vol 87 (5) ◽  
pp. 1337-1343 ◽  
Author(s):  
Ellen S. Beaumont ◽  
John C. Goold
Keyword(s):  
Reference Points ◽  
Halichoerus Grypus ◽  
Field Site ◽  
Identification Process ◽  
Black And White ◽  
Photo Identification ◽  
North Wales ◽  
Accessible Method ◽  
Rectangular Area ◽  
Fixed Reference

A method was developed to assist in the photo-identification of individual grey seals (Halichoerus grypus). Fixed reference points of the eye and ear were used to define a rectangular area of pelage on the seal's head, termed the identifier patch (IP). Extracted IPs were converted to binary masks, and the percentage of black pixelation within each mask was evaluated. Multiple images of the same head profile gave masks with similar patterns and percentage of black pixelation (mean standard deviation 3.3% (±1.6%)). The low level of ‘within seal’ variability enabled ‘between seal’ images to be separated on the basis of percentage of black pixelation. Subsequent matching was achieved by eye using the mask pattern to complete the identification process. Successful matching of seal images, collected two years and nine months apart, at a North Wales field site was accomplished using this method. Pattern-matching trials using 88 untrained volunteers showed the extracted black and white mask to be a superior visual cue for separating individual seals compared to straightforward inspection of photographs. All volunteers identified a greater number of correct matches using the mask-matching method. This method shows promise in providing a cheap and accessible system to order and search image databases.

Improved Instantaneous Current Control for High-Power Three-Phase Dual-Active Bridge DC–DC Converters

2014 ◽  
Vol 29 (8) ◽  
pp. 4067-4077 ◽  
Author(s):  
Stefan P. Engel ◽  
Nils Soltau ◽  
Hanno Stagge ◽  
Rik W. De Doncker
Keyword(s):  
High Power ◽  
Current Control ◽  
Dual Active Bridge ◽  
Three Phase ◽  
Instantaneous Current
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