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Huai Wang

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
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Journal ArticleDOI
TL;DR: In this paper, the authors classified the capacitors condition monitoring methods into three categories and summarized the state-of-the-art research and the future opportunities targeting for industry applications.
Abstract: Capacitors are one type of reliability-critical components in power electronic systems. In the last two decades, many efforts in academic research have been devoted to the condition monitoring of capacitors to estimate their health status. Industry applications are demanding more reliable power electronics products with preventive maintenance. Nevertheless, most of the developed capacitor condition monitoring technologies are rarely adopted by industry due to the complexity, increased cost, and other relevant issues. An overview of the prior-art research in this area is therefore needed to justify the required resources and the corresponding performance of each key method. It serves to provide a guideline for industry to evaluate the available solutions by technology benchmarking, as well as to advance the academic research by discussing the history development and the future opportunities. Therefore, this paper first classifies the capacitor condition monitoring methods into three categories, then the respective technology evolution in the last two decades is summarized. Finally, the state-of-the-art research and the future opportunities targeting for industry applications are given.

159 citations

Journal ArticleDOI
TL;DR: In this article, a frequency adaptive selective harmonic control (FA-SHC) scheme is proposed for grid-connected inverters to optimally mitigate feed-in current harmonics, which consists of multiple parallel recursive (nk ± m)-order (k = 0,1,2,..., and m ≤ n/2) harmonic control modules with independent control gains.
Abstract: In this paper, a frequency adaptive selective harmonic control (FA-SHC) scheme is proposed. The FA-SHC method is developed from a hybrid SHC scheme based on the internal model principle, which can be designed for grid-connected inverters to optimally mitigate feed-in current harmonics. The hybrid SHC scheme consists of multiple parallel recursive (nk ± m)-order (k = 0,1,2,. . ., and m ≤ n/2) harmonic control modules with independent control gains, which can be optimally weighted in accordance with the harmonic distribution. The hybrid SHC, thus, offers an optimal tradeoff among cost, complexity, and also performance in terms of high accuracy, fast response, easy implementation, and compatible design. The analysis and synthesis of the hybrid SHC are addressed. More important, in order to deal with the harmonics in the presence of grid frequency variations, the hybrid SHC is transformed into the FA-SHC, being the proposed fractional-order controller, when it is implemented with a fixed sampling rate. The FA-SHC is implemented by substituting the fractional-order elements with the Lagrange-polynomial-based interpolation filters. The proposed FA-SHC scheme provides fast on-line computation and frequency adaptability to compensate harmonics in grid-connected applications, where the grid frequency is usually varying within a certain range (e.g., 50 ± 0.5 Hz). Experimental tests have demonstrated the effectiveness of the proposed FA-SHC scheme in terms of accurate frequency adaptability and also fast transient response.

157 citations

Proceedings ArticleDOI
16 Mar 2014
TL;DR: In this paper, the authors explored reactive power injection (RPI) strategies for single-phase photovoltaic (PV) systems in low-voltage ride-through (LVRT) operation.
Abstract: As the development and installation of photovoltaic (PV) systems are still growing at an exceptionally rapid pace, relevant grid integration policies are going to change consequently in order to accept more PV systems in the grid. The next generation PV systems will play an even more active role like what the conventional power plants do today in the grid regulation participation. Requirements of ancillary services like Low-Voltage Ride-Through (LVRT) associated with reactive current injection and voltage support through reactive power control, have been in effectiveness in some countries. Those advanced features can be provided by next-generation PV systems, and will be enhanced in the future to ensure an even efficient and reliable utilization of PV systems. In the light of this, Reactive Power Injection (RPI) strategies for single-phase PV systems are explored in this paper. The RPI possibilities are: a) constant average active power control, b) constant active current control, c) constant peak current control and d) thermal optimized control strategy. All those strategies comply with the currently active grid codes, but are with different objectives. The thermal optimized control strategy is demonstrated on a 3 kW single-phase PV system by simulations. The other three RPI strategies are verified experimentally on a 1 kW singe-phase system in LVRT operation mode. Those results show the effectiveness and feasibilities of the proposed strategies with reactive power control during LVRT operation. The design and implementation considerations for the characterized strategies are also discussed.

150 citations

01 Jan 2016
TL;DR: In this article, the authors present a review on the improvement of reliability of dc link in power electronic converters from two aspects: reliability-oriented dc-link design solutions; and conditioning monitoring of DC-link capacitors during operation.
Abstract: DC-link capacitors are an important part in the majority of power electronic converters which contribute to cost, size and failure rate on a considerable scale. From capacitor users' viewpoint, this paper presents a review on the improvement of reliability of dc link in power electronic converters from two aspects: 1) reliability-oriented dc-link design solutions; 2) conditioning monitoring of dc-link capacitors during operation. Failure mechanisms, failure modes and lifetime models of capacitors suitable for the applications are also discussed as a basis to understand the physics-of-failure. This review serves to provide a clear picture of the state-of-the-art research in this area and to identify the corresponding challenges and future research directions for capacitors and their dc-link applications.

149 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed a Monte Carlo based analysis method to predict the lifetime consumption of bond wires of IGBT modules in a photovoltaic (PV) inverter, where variations in IGBT parameters (e.g., on-state collector-emitter voltage, lifetime models, and environmental and operational stresses are taken into account in the lifetime prediction.
Abstract: Bond wire fatigue is one of the dominant failure mechanisms in insulated-gate bipolar transistor (IGBT) modules under cyclic stresses. However, there are still major challenges ahead to achieve a realistic bond wire lifetime prediction in field operation. This paper proposes a Monte Carlo based analysis method to predict the lifetime consumption of bond wires of IGBT modules in a photovoltaic (PV) inverter. The variations in IGBT parameters (e.g., on-state collector–emitter voltage), lifetime models, and environmental and operational stresses are taken into account in the lifetime prediction. The distribution of the annual lifetime consumption is estimated based on a long-term annual stress profile of solar irradiance and ambient temperature. The proposed method enables a more realistic lifetime prediction with a specified confidence level compared to the state-of-the-art approaches. A study case of IGBT modules in a 10-kW three-phase PV inverter is given to demonstrate the procedure of the method. The obtained results of the lifetime distribution can be used to justify the selection of IGBTs for the PV inverter applications and the corresponding risk of unreliability.

147 citations


Cited by
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Journal ArticleDOI

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08 Dec 2001-BMJ
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

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

01 Sep 2010

2,148 citations

Journal ArticleDOI
01 Jan 1977-Nature
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