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.

Design for reliability and robustness tool platform for power electronic systems — Study case on motor drive applications

Abstract: Because of the high cost of failure, the reliability performance of power semiconductor devices is becoming a more and more important and stringent factor in many energy conversion applications. Thus, the need for appropriate reliability analysis of the power electronics emerges. Due to its conventional approach, mainly based on failure statistics from the field, the reliability evaluation of the power devices is still a challenging task. In order to address the given problem, a MATLAB based reliability assessment tool has been developed. The Design for Reliability and Robustness (DfR2) tool allows the user to easily investigate the reliability performance of the power electronic components (or sub-systems) under given input mission profiles and operating conditions. The main concept of the tool and its framework are introduced, highlighting the reliability assessment procedure for power semiconductor devices. Finally, a motor drive application is implemented and the reliability performance of the power devices is investigated with the help of the DfR2 tool, and the resulting reliability metrics are presented.

Study on Oscillations During Short Circuit of MW-Scale IGBT Power Modules by Means of a 6-kA/1.1-kV Nondestructive Testing System

Abstract: This paper uses a 6-kA/1.1-kV nondestructive testing system for the analysis of the short-circuit behavior of insulated-gate bipolar transistor (IGBT) power modules. A field-programmable gate array enables the definition of control signals to an accuracy of 10 ns. Multiple 1.7-kV/1-kA IGBT power modules displayed severe divergent oscillations, which were subsequently characterized. Experimental tests indicate that nonnegligible circuit stray inductance plays an important role in the divergent oscillations. In addition, the temperature dependence of the transconductance is proposed as an important element in triggering for the oscillations.

Simplified Multi-time Scale Thermal Model Considering Thermal Coupling in IGBT Modules

Abstract: In the reliability evaluation of power electronic systems, one of the challenges is to model the thermal profiles across multiple time scales, i.e., from switching cycles at nano-or micro-seconds to annual or even longer-time mission profiles. Without consideration of the dissimilarity of thermal behaviors under different time scales, a single thermal model usually leads to either considerable modeling errors or heavy computational burden. Based on the frequency response of thermal impedances, this paper proposes a novel and simplified thermal model to analyze mission profiles with multiple time scales. It enables a computational-efficient thermal stress analysis for power semiconductors, including the thermal coupling in device packages. The theoretical results are verified by experimental testing.

The impact of grid unbalances on the reliability of DC-link capacitors in a motor drive

Abstract: DC-link capacitor is one of the reliability-critical components in motor drive applications, which contributes to a considerable cost, size and failure. Its reliability performance depends on both inherent physical strength and external loading. The grid unbalances could alter the electro-thermal stresses of key components in a motor drive. Therefore, this paper investigates the impact of grid voltage amplitude and phase unbalances on the lifetime of DC-link capacitors used in a standard three-phase motor drive. The theoretical stress models and experimental measurements of the capacitor voltages and ripple currents are presented. The relationship between the DC-link capacitor lifetime and the level of unbalances and loads are discussed based on a 7.5 kW motor drive system. The results serve as a guideline to size the DC-link capacitors to be robust enough at the presence of grid unbalance conditions.

Artificial Intelligence-Aided Thermal Model Considering Cross-Coupling Effects

Abstract: This letter proposes an artificial intelligence-aided thermal model for power electronic devices/systems considering thermal cross-coupling effects. Since multiple heat sources can be applied simultaneously in the thermal system, the proposed method is able to characterize model parameters more conveniently compared to existing methods where only single heat source is allowed at a time. By employing simultaneous cooling curves, linear-to-logarithmic data re-sampling, and differentiated power losses, the proposed artificial neural network-based thermal model can be trained with better data richness and diversity while using fewer measurements. Finally, experimental verifications are conducted to validate the model capabilities.

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.