Author
Huai Wang
Other affiliations: Yangtze University, City University of Hong Kong
Bio: Huai Wang is an academic researcher from Aalborg University. The author has contributed to research in topics: Capacitor & Power electronics. The author has an hindex of 38, co-authored 328 publications receiving 7480 citations. Previous affiliations of Huai Wang include Yangtze University & City University of Hong Kong.
Papers
More filters
••
20 Mar 2016TL;DR: In this paper, the authors proposed an advanced lifetime prediction method, which takes into account the field operation mission profiles and the statistical properties of the life data available from accelerated degradation testing, and identifies also the key variables (e.g., heat sink parameters and lifetime-matching of LED drivers) that can be designed to achieve a specified lifetime and reliability level.
Abstract: Light-Emitting Diodes (LEDs) has become a very promising alternative lighting source with the advantages of longer lifetime and higher efficiency than traditional ones. The lifetime prediction of LEDs is important to guide the LED system designers to fulfill the design specifications and to benchmark the cost-competitiveness of different lighting technologies. The existing lifetime data released by LED manufacturers or standard organizations are usually applicable only for specific temperature and current levels. Significant lifetime discrepancies may be observed in field operations due to the varying operational and environmental conditions during the entire service time (i.e., mission profiles). To overcome the challenge, this paper proposes an advanced lifetime prediction method, which takes into account the field operation mission profiles and the statistical properties of the life data available from accelerated degradation testing. It identifies also the key variables (e.g., heat sink parameters and lifetime-matching of LED drivers) that can be designed to achieve a specified lifetime and reliability level. Two case studies of an indoor residential lighting and an outdoor street lighting application are presented to demonstrate the prediction procedures and the impact of different mission profiles on the lifetime of LEDs.
8 citations
••
TL;DR: In this paper, a new reliability testing concept for the dc-link capacitor in PV inverters is proposed in contrast to the conventional method, the proposed reliability testing method designs the test profile through the modification of the original mission profile (e.g., solar irradiance and ambient temperature) in order to maintain the test condition as close to the real application as possible.
Abstract: The dc-link capacitor is considered as a weak component in photovoltaic (PV) inverter systems and its reliability needs to be evaluated and tested during the product development. Conventional reliability testing methods for capacitors are typically carried out under constant loading conditions, which do not reflect the real operating conditions (e.g., mission profile) of the dc-link capacitor in PV inverters. To address this issue, a new reliability testing concept for the dc-link capacitor in PV inverters is proposed in this article. In contrast to the conventional method, the proposed reliability testing method designs the test profile through the modification of the original mission profile (e.g., solar irradiance and ambient temperature) in order to maintain the test condition as close to the real application as possible. A certain acceleration factor is applied during the mission profile modification based on the lifetime model of the capacitor, in order to increase the thermal stress of the dc-link capacitor during test, and thereby effectively reduce the testing time.
8 citations
••
01 Dec 2015TL;DR: In this paper, the authors classified the electrical energy conversion by power electronic systems into four categories: 1. Voltage conversion and power conversion for both direct current (DC) and alternate current (AC) 2. Frequency conversion 3. Wave-shape conversion 4. Polyphase conversion
Abstract: Electrical energy conversion by power electronic systems can be classified into the following four categories: 1. Voltage conversion and power conversion for both direct current (DC) and alternate current (AC) 2. Frequency conversion 3. Wave-shape conversion 4. Poly-phase conversion.
8 citations
••
27 Sep 2018
TL;DR: The reliability of the filter capacitor bank is obtained based on its individual capacitor reliability curves and reliability block diagram method and the relationship between the lifetime of the capacitor bank and the single capacitor is demonstrated.
Abstract: Growing with the increased adoption of renewable energy for the power generation, the reliable and cost-effective operation of grid-connected inverters is of more and more importance. A filter is interfaced between an inverter and the utility grid to reduce the switching harmonics. According to the modulation scheme and the LCL filter impedance, the electrical stresses of the filter capacitor can be thoroughly investigated. With the help of the electro-thermal model, its long-term thermal stress can be obtained based on the mission profile like wind speed, ambient temperature. The reliability of the filter capacitor bank is obtained based on its individual capacitor reliability curves and reliability block diagram method. A case study on a 2MW wind turbine system demonstrates the relationship between the lifetime of the capacitor bank and the single capacitor. Moreover, the severe voltage and current stresses of the filter capacitors are analyzed during abnormal operations (e.g., fault ride-through) with asymmetrical parasitic parameters.
8 citations
••
TL;DR: The multi-port thermal model is verified by simulations and experimental results and confirms that more accurate temperature estimation can be achieved compared with the thermal model without the thermal coupling effect.
8 citations
Cited by
More filters
••
[...]
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.
Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …
33,785 citations
•
28,685 citations
01 Nov 2000
TL;DR: In this paper, the authors compared the power density characteristics of ultracapacitors and batteries with respect to the same charge/discharge efficiency, and showed that the battery can achieve energy densities of 10 Wh/kg or higher with a power density of 1.2 kW/kg.
Abstract: The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.
2,437 citations
••
TL;DR: Bergh and P.J.Dean as discussed by the authors proposed a light-emitting diode (LEDD) for light-aware Diodes, which was shown to have promising performance.
Abstract: Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.
1,560 citations