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      • An LCCL Filter and Its Application to a Half-Bridge APF

        Jingyang Fang,Guochun Xiao,Yan Zhang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

        In this paper, a novel high order power filter is proposed, named the LCCL filter. Compared with the traditional LCL filter, the LCCL filter composes a parallel resonant branch loop at the switching frequency by paralleling a small capacitor with the line side inductor. The parallel resonance enables the line side branch loop to exhibit infinite impedance at the switching frequency. Particularly, it can attenuate the switching frequency current ripple components much better than the LCL filter, thus decreases grid current THD. Compared with an LLCL filter, the LCCL filter exhibits better attenuation ability in the high frequency domain when the source impedance is considered. Besides, a capacitorcurrent- based active damping controller is easy to design on the basis of the LCCL filter. A half-bridge APF is taken as an example in this paper to discuss the parameter selection and the controller design method based on the LCCL filter. At last, simulation and experimental results validate the feasibility of the proposed LCCL filter.

      • Inertia Emulation through Supercapacitor Energy Storage Systems

        Ruiqi Zhang,Jingyang Fang,Yi Tang 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

        To establish a more reliable, sustainable and high-efficiency smart grid, renewable energy sources (RESs) have been increasingly integrated into modern power systems. Since RESs are normally coupled to electrical grids through grid-connected power converters, which do not possess any rotational inertia as conventional synchronous generators do, modern power systems will face frequency control challenges as the power system inertia continues to decrease. To address the lack of inertia concern, supercapacitor energy storage systems (SESSs) are implemented in this paper to generate virtual inertia by proportionally linking the grid frequency to the voltage references of supercapacitors. In this way, the improvements of inertia and frequency control can be achieved. More importantly, this paper discloses that the basic inertia control scheme introduces inertia emulation errors under large frequency disturbances. As a solution, this paper presents a nonlinear inertia control scheme, which ensures fair inertia emulation even under large frequency disturbances. Simulation and experimental results are finally presented to verify the effectiveness of the virtual inertia and the control schemes.

      • A Frequency Deadband-Based Virtual Inertia Control for Grid-Connected Power Converters

        Nanjun Lu,Jingyang Fang,Yi Tang,Branislav. Hredzak 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

        Unlike synchronous generators, renewable generators, e.g. photovoltaic (PV) arrays and wind turbines, cannot provide rotating inertia when connected to the grid through power converters. As a result, excessive grid frequency deviations are likely to occur in the event of generator tripping and/or load shedding. An effective approach to increase inertia is achieved by proportionally associating the dc-link voltage of grid-connected power converters with the grid frequency, allowing power converters to generate a fixed amount of virtual inertia for frequency support. To further develop this idea, this paper proposes a frequency deadband-based virtual inertia controller for power converters to perform inertia responses during frequency events. The proposed controller enables the increase of inertia in a shorter time duration, leading to an improved frequency nadir and a reduction of the energy required for inertia emulation. Finally, simulated and experimental results are presented to verify its effectiveness.

      • Exploration of Time-Delay Effect on the Stability of Grid-Connected Power Converters with Virtual Inertia

        Haoxin Yang,Jingyang Fang,Yi Tang 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

        The lack of inertia contributions from renewable generators, which are essentially power electronic converters in replacement of synchronous generators, may greatly degrade the frequency regulation performance. As a solution, distributed virtual inertia provided by gridconnected power converters has been introduced as an effective approach to improve power system inertia. However, time-delays, which can be introduced by signal measurement, converter control, and communication, are ignored in the existing virtual inertia control implementations. To fill this research gap, this paper presents a detailed analysis of the effect of time-delays on virtual inertia control. It is revealed that instability will happen when the virtual inertia is greater than the existing power system inertia regardless of time-delays. In other cases, the system stability depends on time-delays, together with other design parameters. For verification, the experimental results are presented, which are consistent with the theoretical analysis.

      • Current Self-Balancing Mechanism in ZVS Full-Bridge Converters

        Hongchang Li,Michael A. de Rooij,Jingyang Fang,Haoxin Yang,Yi Tang 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

        Full-bridge converters are widely used in isolated dc-dc conversion and wireless power transfer systems. A full-bridge converter can operate in zero-voltageswitching (ZVS) mode with the assistance of an inductive branch that connects the two switch nodes in parallel with the load. The inductive branch provides a ZVS current and has a very low resistance. A tiny volt-second imbalance between the switch nodes may cause a large current bias on the branch. However, it can be demonstrated experimentally that the current on the branch can be almost self-balanced without any dc blocking capacitor or balancing control. This paper quantitatively studies the current self-balancing mechanism and shows that the dead-time switch-node voltage can give a strong negative feedback effect that pushes the current bias toward zero. Experimental verification was carried out on a gallium-nitride device-based converter.

      • KCI등재

        Quantile regression for robust inference on varying coefficient partially nonlinear models

        Jing Yang,Fang Lu,Hu Yang 한국통계학회 2018 Journal of the Korean Statistical Society Vol.47 No.2

        In this paper, we propose a robust statistical inference approach for the varying coefficient partially nonlinear models based on quantile regression. A three-stage estimation procedure is developed to estimate the parameter and coefficient functions involved in the model. Under some mild regularity conditions, the asymptotic properties of the resulted estimators are established. Some simulation studies are conducted to evaluate the finite performance as well as the robustness of our proposed quantile regression method versus the well known profile least squares estimation procedure. Moreover, the Boston housing price data is given to further illustrate the application of the new method.

      • KCI등재

        Genetic variation and population structure of the oriental fruit moth Grapholita molesta in Shanxi, a major pome fruits growing region in North China

        Jing Yang,Zhong-Fang Liu,Ji-Qiao Fan,Yu-PengWu,Rui-Yan Ma,Ren-Jun Fan 한국응용곤충학회 2016 Journal of Asia-Pacific Entomology Vol.19 No.4

        Grapholitamolesta, commonly known as the oriental fruit moth, is one of the most destructive fruit pests both in China and in other regions of the world. We examined the genetic diversity and population structures of G. molesta populations from 11 locations in a major pome fruit production region (Shanxi province) in North China using seven microsatellite markers and sequence variations in two mitochondrial genes. We found that G.molesta in the studied region exhibited high levels of genetic diversity. Among 271 individual insects examined using microsatellite markers, mean number of alleles ranged from 5.86 to 9.00 with average 8.01. Population structure analysis revealed that populations from the eleven sampling sites formed two clusters without apparent distance isolation. Cluster 1 consisted of eight populations distributed in five regions of the sampling sites, whereas Cluster 2 consisted of three populations distributed in two distant locations of the sampling sites. Genetic exchange analysis revealed that about half of the haplotypes were shared among over 90% individual insects from different regions. Our results indicated that the population structure and genetic exchange of G. molesta in the studied region might have been affected by limited dispersal ability of the insect, environmental condition, colonization history and human-mediated dispersal. These findings should provide useful information for the implementation of area-wide pest management and for further characterization of genetic variation and population structure of this economically important pest.

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