The Experts below are selected from a list of 98274 Experts worldwide ranked by ideXlab platform
Huai Wang - One of the best experts on this subject based on the ideXlab platform.
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reliability study of input side Capacitors in impedance source pv microconverters
Conference of the Industrial Electronics Society, 2019Co-Authors: Elizaveta Liivik, Huai Wang, Dmitri Vinnikov, Andrii Chub, Yanfeng Shen, Frede BlaabjergAbstract:This paper discusses reliability issues of three different types of Capacitors (ceramic, electrolytic and film) applied in the input side of an impedance-source photovoltaic (PV) microconverter having an ultra-wide dc gain range. The study considers a wear-out failure analysis based on a daily PV mission profile. The general operation and control principle are first described. Then the selection criteria of the Capacitors are analyzed. Experimental measurements of Capacitors temperature are translated into accumulated damage using their corresponding lifetime models. Finally, conclusions are drawn regarding the applicability of different Capacitor technologies in impedance-source PV microconverters, where the film Capacitor has the lowest damage.
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lifetime estimation of dc link Capacitors in adjustable speed drives under grid voltage unbalances
IEEE Transactions on Power Electronics, 2019Co-Authors: Haoran Wang, Huai Wang, Pooya Davari, Dinesh Kumar, Firuz ZareAbstract:Electrolytic Capacitor with a dc-side inductor is a typical dc-link filtering configuration in grid-connected diode rectified adjustable speed drives (ASDs). The criteria to size the dc-link filter are mainly from the aspects of stability and power quality. Nevertheless, the reliability of the dc-link filter is also an essential performance factor to be considered, which depends on both the component inherent capability and the operational conditions (e.g., electrothermal stresses) in the field operation. Nowadays, unbalanced voltage has the most frequent occurrence in many distribution networks. It brings more electrical-thermal stress to the component, affecting the reliability of the Capacitors. In order to study the reliability performance of the LC filter in an ASD system quantitatively, this paper proposes a mission profile based reliability evaluation method for Capacitors. Different from the conventional lifetime estimation, a nonlinear accumulated damage model is proposed for the long-term estimation, considering the nonlinear process of equivalent series resistor growth and capacitance reduction during the degradation. Based on the proposed lifetime estimation procedure, four case studies are investigated: first, lifetime benchmarking of Capacitors in LC filtering and slim Capacitor filtering configurations; second, scalability analysis for the lifetime of Capacitors in terms of system power rating and grid-unbalanced levels; third, lifetime estimation of Capacitors in the dc-link filter with long-term mission profile; and fourth, the impact of the Capacitor sizing on the lifetime of the dc-link Capacitor under grid-balanced and grid-unbalanced conditions. The results serve as a guideline for proper selection of dc-link configurations and parameters to fulfill a specification in ASDs.
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Reliability Assessment of Hybrid Capacitor Bank Using Electrolytic- and Film-Capacitors in Three-Level Neutral-Point-Clamped Inverters
2019 IEEE Applied Power Electronics Conference and Exposition (APEC), 2019Co-Authors: Mengxing Chen, Huai Wang, Haoran Wang, Xiongfei WangAbstract:Hybrid Capacitor banks using electrolytic Capacitors (E-Caps) and film Capacitors (F-Caps) provide a cost-effective solution for DC links. However, the hybrid ratio between two types of Capacitors is mostly experience based. This paper studies the quantitative solution to size the hybrid ratio for Capacitor banks from a reliability point of view. Considering the parasitic parameters and thermal inertia of individual Capacitors in a bank, an analytical model to obtain the electro-thermal performance for the individual type of Capacitor is proposed. The quantitative relationship between the hybrid ratio and Capacitor-bank reliability is acquired by applying a mission profile based reliability analysis. In addition, a DC-link Capacitor bank in three-level neutral-point-clamped inverter is designed and implemented to validate the accuracy of the proposed method.
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impedance characteristics modeling of a two terminal active Capacitor
Workshop on Control and Modeling for Power Electronics, 2017Co-Authors: Haoran Wang, Huai WangAbstract:Conventional Capacitors contribute to a considerable scale of system level size, cost and failure, and suffer from one or more issues on energy density, cost, and reliability. A two-terminal active Capacitor, which has the same level of convenience as passive Capacitors, is proposed recently to overcome the above issues. In this paper, the modeling of the active Capacitor is investigated and a voltage feed-forward compensation scheme is proposed for overshoot reduction. Therefore, the impedance, equivalent capacitance, ESR, and ESL, of the active Capacitor can be specified. A case study based on a single-phase full-bridge rectifier with an active Capacitor demonstrates the theoretical analyses.
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Lifetime estimation of electrolytic Capacitors in a fuel cell power converter at various confidence levels
2016 IEEE 2nd Annual Southern Power Electronics Conference (SPEC), 2016Co-Authors: Dao Zhou, Huai Wang, Frede BlaabjergAbstract:DC Capacitors in power electronic converters are a major constraint on improvement of the power density and the reliability. In this paper, according to the degradation data of tested Capacitors, the lifetime model of the component is analyzed at various confidence levels. Then, the mission profile based lifetime expectancy of the individual Capacitor and the Capacitor bank is estimated in a fuel cell backup power converter operating in both standby mode and operation mode. The lifetime prediction of the Capacitor banks at different confidence levels is also obtained.
Yongzi Jing - One of the best experts on this subject based on the ideXlab platform.
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one inductor based auxiliary circuit for dc link Capacitor voltage equalisation of diode clamped multilevel converter
Iet Power Electronics, 2013Co-Authors: Zeliang Shu, Haifeng Zhu, Na Ding, Yongzi JingAbstract:The one-inductor-based auxiliary balancing circuit is proposed to equalise dc-link Capacitor voltages of diode-clamped multilevel converters (DCMC) in this study. After theoretical analysis of balancing unit in traditional one-level-based balancing schemes, one-inductance-based schemes are designed according to the same operating principle. Via some conducted diodes and switches by simple control, this circuit provides energy exchange paths of all the dc-link Capacitors by only one inductor. Firstly, the inductor absorbs energy from the Capacitor with the highest voltage. Then, this Capacitor is discharged and its voltage will decrease. Secondly, the inductor releases energy to the Capacitor with the lowest voltage. Then, this Capacitor is charged and its voltage will increase. After performing this operation a number of times, all the voltages of the dc-link Capacitors will finally reach the same value. The circuit configurations, conducting paths and control strategies of one-inductor-based scheme for five-level DCMC are analysed, respectively. Owing to small equivalent resistances of Capacitor and inductor, the small power loss could be achieved. Simulations and experiments have been carried out. The steady-state and dynamic results verify the effective balancing performance of this circuit.
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voltage balancing approaches for diode clamped multilevel converters using auxiliary Capacitor based circuits
IEEE Transactions on Power Electronics, 2013Co-Authors: Zeliang Shu, Zhiyong Wang, Daqiang Qiu, Yongzi JingAbstract:An auxiliary Capacitor-based balancing approach is adopted in this paper to equalize the dc-link Capacitor voltages of a diode-clamped multilevel converter (DCMC). Four balancing circuits, including the generalized, one-level-Capacitor, one-Capacitor, and simplified one-Capacitor-based configurations are discussed for a five-level DCMC system. These configurations are different in connection of the auxiliary circuits and numbers of the Capacitors and switches, but they work on the same principle called ping-pong operation by utilizing the auxiliary Capacitor as an equalizer between the Capacitors of different voltages. The unbalance phenomenon, ping-pong principle, circuit configurations, and their switching schemes are analyzed, respectively. The superiorities of the proposed approach include balancing operation regardless of load power factor and modulation index, control simplicity, and independence from main circuits when compared to the traditional approaches. Simulations and experimental results verified the performances using the proposed balancing circuits and control strategies.
Chinglien Huang - One of the best experts on this subject based on the ideXlab platform.
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solving the Capacitor placement problem in a radial distribution system using tabu search approach
IEEE Transactions on Power Systems, 1996Co-Authors: Yannchang Huang, Hongtzer Yang, Chinglien HuangAbstract:In this paper, the Capacitor placement problem in a radial distribution system is formulated and solved by a Tabu Search (TS) based solution algorithm. The Capacitor placement problem considers practical operating constraints of Capacitors, load growth, capacity of the feeder and the upper and lower bound constraints of voltage at different load levels to minimize the investment cost of Capacitors and system energy loss. A sensitivity analysis method is used to select the candidate installation locations of the Capacitors to reduce the search space of this problem a priori. Comparison results of the TS method with the simulated annealing (SA) show that the proposed TS method can offer the nearly optimal solution to the Capacitor placement problem within reasonable computing time.
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solution to Capacitor placement problem in a radial distribution system using tabu search method
International Conference on Energy Management and Power Delivery, 1995Co-Authors: Hongtzer Yang, Yannchang Huang, Chinglien HuangAbstract:In this paper, the Capacitor placement problem in a radial distribution system is formulated and solved by a tabu search (TS) based solution algorithm. The Capacitor placement problem considers practical operating constraints of Capacitors, load growth, capacity of the feeder and the upper and lower bound constraints of voltage at different load levels to minimize the investment cost of Capacitors and system energy loss. A sensitivity analysis method is used to select the candidate installation locations of the Capacitors to reduce the search space of this problem a priori. Comparison results of the TS method with the simulated annealing (SA) show that the proposed TS method can offer the nearly optimal solution to the Capacitor placement problem within reasonable computing time.
J P Zheng - One of the best experts on this subject based on the ideXlab platform.
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The Limitations of Energy Density for Electrochemical Capacitors
Journal of The Electrochemical Society, 1997Co-Authors: J P ZhengAbstract:Electrochemical Capacitors can be divided into two types depending on whether the salt concentration in the electrolyte changes during charging and discharging. In the first type of Capacitor, such as double-layer Capacitors, the salt concentration in the electrolyte reduces during the charging of the Capacitor. The maximum energy density of this type of Capacitor will depend not only on the specific capacitance and the operating voltage, but also on the salt concentration of the electrolyte. In this paper, a formula describing the dependence of energy density on specific capacitance, operating voltage, and salt concentration is given based on the optimized weight (or volune) ratio of the electrode material and the electrolyte. It shows that for electrochemical Capacitors using nonaqueous electrolytes, the maximum energy density of the Capacitor will be limited mainly by the low salt concentrations of the electrolyte. The relationship between the energy density and the mass density of the electrode is also given. The optimum mass density of the electrode can be obtained based on the value of the theoretical energy density for Capacitors with different electrolytes. In the second type of Capacitor, such as pseudoCapacitors with metal oxide electrodes, the salt concentration in the electrolyte remains constant during charging and discharging. The maximum energy denisty of this type of Capacitor will be limited mainly by specific capacitance and operating voltage.
Zeliang Shu - One of the best experts on this subject based on the ideXlab platform.
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one inductor based auxiliary circuit for dc link Capacitor voltage equalisation of diode clamped multilevel converter
Iet Power Electronics, 2013Co-Authors: Zeliang Shu, Haifeng Zhu, Na Ding, Yongzi JingAbstract:The one-inductor-based auxiliary balancing circuit is proposed to equalise dc-link Capacitor voltages of diode-clamped multilevel converters (DCMC) in this study. After theoretical analysis of balancing unit in traditional one-level-based balancing schemes, one-inductance-based schemes are designed according to the same operating principle. Via some conducted diodes and switches by simple control, this circuit provides energy exchange paths of all the dc-link Capacitors by only one inductor. Firstly, the inductor absorbs energy from the Capacitor with the highest voltage. Then, this Capacitor is discharged and its voltage will decrease. Secondly, the inductor releases energy to the Capacitor with the lowest voltage. Then, this Capacitor is charged and its voltage will increase. After performing this operation a number of times, all the voltages of the dc-link Capacitors will finally reach the same value. The circuit configurations, conducting paths and control strategies of one-inductor-based scheme for five-level DCMC are analysed, respectively. Owing to small equivalent resistances of Capacitor and inductor, the small power loss could be achieved. Simulations and experiments have been carried out. The steady-state and dynamic results verify the effective balancing performance of this circuit.
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voltage balancing approaches for diode clamped multilevel converters using auxiliary Capacitor based circuits
IEEE Transactions on Power Electronics, 2013Co-Authors: Zeliang Shu, Zhiyong Wang, Daqiang Qiu, Yongzi JingAbstract:An auxiliary Capacitor-based balancing approach is adopted in this paper to equalize the dc-link Capacitor voltages of a diode-clamped multilevel converter (DCMC). Four balancing circuits, including the generalized, one-level-Capacitor, one-Capacitor, and simplified one-Capacitor-based configurations are discussed for a five-level DCMC system. These configurations are different in connection of the auxiliary circuits and numbers of the Capacitors and switches, but they work on the same principle called ping-pong operation by utilizing the auxiliary Capacitor as an equalizer between the Capacitors of different voltages. The unbalance phenomenon, ping-pong principle, circuit configurations, and their switching schemes are analyzed, respectively. The superiorities of the proposed approach include balancing operation regardless of load power factor and modulation index, control simplicity, and independence from main circuits when compared to the traditional approaches. Simulations and experimental results verified the performances using the proposed balancing circuits and control strategies.
