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.

Analysis of solar panel’s lumped equivalent circuit parameters using LASSO

Abstract: The power output of a solar panel depends on the level of degradation and external factors, such as temperature and solar irradiation. The changes in the power output caused by temperature and irradiation fluctuations coincide with the changes due to degradation. Therefore, a common way of degradation determination requires the knowledge of external factors. This work investigates a modeling of the panel power output at the reference state without the knowledge of the external factors. Firstly, a sparse regression modeling is used to identify relevant lumped equivalent circuit parameters, which capture the reference state of the solar panel. The p-n junction capacitance is found to be an important indicator of external factors tied to the panel’s state of health. Secondly, a set of regression models for modelling the solar panel reference state are tested to distinguish a permanent 5% drop in power output from a regular temperature and irradiation fluctuations, without the information of the temperature and irradiation.

Design and Benchmark of Passive and Active Inductors for a 7.5 kW Motor Drive

Abstract: Volume, weight, and cost are considered as the drawbacks of the passive LC filters. Recently, activation of passive inductor concept has been proposed to break these limits, which emulates the impedance of passive inductor by using power semiconductor circuits. To explore the benefits of this new concept in motor drive applications, this paper studies the reliability-oriented design of the active inductor for a 7.5 kW commercial motor drive product, and benchmarks the performance of active inductors and passive inductors in terms of volume, weight, and cost. Prototypes are manufactured to verify the accuracy of the modeling results, which proves that the volume, weight, and cost of an active inductor for a 7.5 kW motor drive are 90.5%, 66.7% and 91.2% of the passive inductor, respectively.

A Robust Passive Damping Method for LLCL-Filter-Based Grid-Tied Inverters to Minimize the Effect of

Abstract: In order to minimize the effect of the grid harmonic voltages, harmonic compensation is usually adopted for a grid-tied inverter. However, a large variation of the grid inductance challenges the system stability in case a high-order passive filter is used to connect an inverter to the grid. Although in theory, an adaptive controller can solve this problem, but in such a case the grid inductance may need to be detected online, which will complicate the control system. This paper investigates the relationship between the maximum gain of the controller that still keeps the system stable and the Q-factor for a grid-tied inverter with an RL series or an RC parallel damped high-order power filter. Then, a robust passive damping method for LLCL-filter-based grid-tied inverters is proposed, which effectively can suppress the possible resonances even if the grid inductance varies in a wide range. Simulation and experimental results are in good agreement with the theoretical analysis.

Differential Model EMI Filter Analysis for Interleaved Boost PFC Converters Considering Optimal Phase Shifting

Abstract: Interleaved Power Factor Correction (PFC) has become a most popular topology from efficiency and power density point of view over single-switch boost PFC. The dependency of the Differential Model (DM) Electromagnetic Interference (EMI) noise magnitude on input current ripple leads to investigate the influence of the interleaved technique on EMI noise. Hence, this paper provides a comprehensive investigation for the design of DM EMI filter a single-phase interleaved PFC targeting to minimize component size. It is shown how different operation modes (continuous and discontinuous conduction mode) and switching frequency may influence the required filter attenuation and, consequently, the EMI filter size. Furthermore, the impact of the number of interleaved stages and optimal phase shifting on the required filter attenuation is analyzed. Finally, the influence of optimal phase shifting achieve an overall minimum EMI filter corner frequency is discussed. Experimental results from a 2 kW interleaved single-phase boost PFC converter validate the effectiveness of the proposed optimal phase shifting method.

Uneven Inter-turn Voltage Distribution among Windings of Medium-voltage Medium/High-frequency Transformers

Abstract: Working under PWM pulse voltage, medium voltage medium/high-frequency transformers may face unevenly distributed electrical stress between inter-turns. This could increase the probability of partial discharge in the winding insulation and thus the risk of premature insulation failure would be higher. To investigate this issue, an equivalent circuit model of a transformer's winding is built. Based on that, simulations on voltage distribution between inter-turns with different voltage rise times, frequencies, material relative permittivity, insulation distance, and number of turns are conducted. The results show that uneven voltage distribution exists in the winding of transformers operating under PWM pulse voltage, with the first two turns suffering from the highest voltage drop. Also, the influence of the above-mentioned parameters on the inter-turn voltage distribution is revealed.

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.