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.

Reliability-Oriented Optimization of the LC Filter in a Buck DC-DC Converter

Abstract: Lifetime is an important performance factor in the reliable operation of power converters. However, the state-of-the-art LC filter design of a buck dc–dc converter is limited to the specifications of voltage and current ripples and constrains in power density and cost without reliability considerations. This paper proposes a method to optimize the design of the LC filters from a reliability perspective, besides other considerations. An enhanced model is derived to quantify the lifetime of the capacitor in the filter considering the electrothermal stress on it. Furthermore, the influence of different design aspects such as the value of capacitance, the value of inductance, and the type of the capacitor have been discussed, focusing on their impacts on the key design objectives, which are the cutoff frequency, lifetime, and volume. Based on the analysis, an optimized design is proposed among different parameter sets. A 1-kW converter prototype is applied to verify the theoretical analysis and simulation.

The Impact of Topology and Mission Profile on the Reliability of Boost-type Converters in PV Applications

Abstract: This paper investigates the impact of different converter topologies and mission profiles on the reliability of dc/dc boost-type PV converters The reliability of three boost-type converters with the same input/output specifications is modeled employing a mission profile-based reliability evaluation method considering non-constant failure rate for the electrical components This study identifies the contribution of active and passive components on the converter reliability for identifying the most failure prone components Furthermore, the applicability of converter structures for different climate conditions is demonstrated seen from the reliability point of view

A reliability-oriented design method for power electronic converters

Abstract: Reliability is a crucial performance indicator of power electronic systems in terms of availability, mission accomplishment and life cycle cost. A paradigm shift in the research on reliability of power electronics is going on from simple handbook based calculations (e.g. models in MIL-HDBK-217F handbook) to the physics-of-failure approach and design for reliability process. A systematic design procedure consisting of various design tools is presented in this paper to design reliability into the power electronic converters since the early concept phase. The corresponding design procedures and reliability prediction models are provided. A case study on a 2.3 MW wind power converter is discussed with emphasis on the reliability critical component IGBT modules.

A novel electro-thermal model for wide bandgap semiconductor based devices

Abstract: This paper propose a novel Electro-Thermal Model for the new generation of power electronics WBG-devices (by considering the SiC MOSFET-CMF20120D from CREE), which is able to estimate the device junction and case temperature. The Device-Model estimates the voltage drop and the switching energies by considering the device current, the off-state blocking voltage and junction temperature variation. Moreover, the proposed Thermal-Model is able to consider the thermal coupling within the MOSFET and its freewheeling diode, integrated into the same package, and the influence of the ambient temperature variation. The importance of temperature loop feedback in the estimation accuracy of device junction and case temperature is studied. Furthermore, the Safe Operating Area (SOA) of the SiC MOSFET is determined for 2L-VSI applications which are using sinusoidal PWM. Thus, by considering the heatsink thermal impedance, the switching frequency and the ambient temperature, the maximum allowed drain current is determined according to the thermal limitations of the device. Finally, dynamic study of MOSFET junction and case temperature is also performed by considering the variation of the ambient temperature and of the load current.

Reduced junction temperature control during low-voltage ride-through for single-phase photovoltaic inverters

Abstract: Future photovoltaic (PV) inverters are expected to comply with more stringent grid codes and reliability requirements, especially when a high penetration degree is reached, and also to lower the cost of energy. A junction temperature control concept is proposed in this study for the switching devices in a single-phase PV inverter in order to reduce the junction temperature stress, and thus to achieve improved reliability of a PV inverter. The thermal stresses of the switching devices are analysed during low-voltage ride-through operation with different levels of reactive power injection, allowing an optimal design of the proposed control scheme with controlled mean junction temperature and reduced junction temperature swings. The effectiveness of the control method in terms of both thermal performance and electrical performance is validated by the simulations and experiments, respectively. Both test results show that single-phase PV inverters with the proposed control approach not only can support the grid voltage recovery in low-voltage ride-through operation but also can improve the overall reliability with a reduced junction temperature.

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.