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.

On the Explainability of Black Box Data-Driven Controllers for Power Electronic Converters

Abstract: This paper proposes to explain the black-box feature of data-driven machine learning (ML) models used for controlling power electronic converters for the first time. As the name suggests, their “black box” feature prevents a clear understanding of the physical insights behind these ML models. It remains a fundamental aspect, if one plans to take action based on a prediction, or deploy a new ML model. Moreover, leaked and corrupted data during the training process can easily augment unexplainable actions from them. To address these issues, we first interpret the actions of the black box models by calculating a conditional entropy for each input with respect to an output. Using this metric, the averaged relationships between each input-output can be mapped and representative conclusions are firstly drawn on identifying erroneous data. Finally, these abnormal data are then removed from the training database to improve the interpretability & classification abilities of the ML model. We illustrate our findings on the performance of a regression based learning tool used for controlling a grid-connected voltage source inverter (VSI).

Safe Operating Area of DC-Link Film Capacitors

Abstract: This letter proposes a safe operating area (SOA) concept for film capacitors in dc-link applications. The SOA is presented by capacitor voltage and ripple current, considering the impact of ambient temperature, degradation, and parameter variance. The theoretical derivations and proof-of-concept experimental verifications are given.

Efficiency Enhancement of Bridgeless Buck-Boost PFC Converter with Unity PF and DC Split to Reduce Voltage Stresses

Abstract: This paper proposes a unity power factor (PF) bridgeless buck-boost power factor correction (PFC) converter to minimize conduction losses caused by the diode bridge. Moreover, compared to the conventional buck-boost PFC converter, the proposed converter has lower voltage stresses across switches, which further improves the overall efficiency of the proposed converter, especially when it operates in the light load conditions. Operation modes with inductors working in the discontinuous conduction mode (DCM) are given in detail, and comparative analysis is conducted to show the proposed converter performance regarding the PF, component stresses, and output ripple. The proposed and conventional converter prototypes with load range of 20∼100 W are built and tested. The obtained results verify merits and theoretical predictions of the proposed.

An Improved di/dt -RCD Detection for Short-Circuit Protection of SiC mosfet

Abstract: Silicon carbide metal-oxide-semiconductor field-effect transistor has a smaller short-circuit tolerance, and hence, requires faster and more accurate short-circuit protection. One prospective method is to combine fast di/dt detection with an integration circuit. The former is for detecting the extremely fast increase of short-circuit current, while the latter is for generating a scaled copy of the short-circuit current for comparison with a threshold. The integration is almost always performed with a resistive–capacitive (RC) low-pass filter due to its simplicity. However, it does not produce consistent results under different load and fault conditions, which can, in turn, cause the detection to fail. An alternative di/dt -RCD (RC + diode) protective circuit has therefore been proposed to offer more accurate and consistent results, irrespective of the fault types. Design equations for the circuit have been derived for implementing an experimental setup, from which results have proven the effectiveness of the proposed di/dt -RCD protection.

I and i

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 …

Ultracapacitors: Why, How, and Where is the Technology

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.

Light-emitting diodes

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.