Multiple Decoupling Current Control Strategies for LCL Type Grid-Connected Converters Based on Complex Vectors under Low Switching Frequencies

Haiyuan Liu,Yang Shi,Yinan Guo,Yingjie Wang,Wenchao Wang 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

In medium-voltage and high-voltage high-power converters, the switching devices need to operate at a low switching frequency toreduce power loss and increase the power capacity. This increases the delay of the signal sampling and PWM. It also makes thecross-couplings of the d-q current components more severe. In addition, the LCL filter has three cross-coupling loops and is prone toresonance. In order to solve these problems, this paper establishes a complex vector model of an LCL type grid-connected converter. Based on this model, two multiple decoupling current control strategies with passive damping / notch damping are proposed for theLCL type grid-connected converter. The proposed strategies can effectively eliminate the cross-couplings of the converter, achieveindependent control of the d-q current components, expand the stable region and suppress the resonance of the LCL filter. Simulation and experimental results verify the correctness of the theoretical analysis and the feasibility of the proposed strategies.

Multiple Decoupling Current Control Strategies for LCL Type Grid-Connected Converters Based on Complex Vectors under Low Switching Frequencies

Liu, Haiyuan,Shi, Yang,Guo, Yinan,Wang, Yingjie,Wang, Wenchao The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

In medium-voltage and high-voltage high-power converters, the switching devices need to operate at a low switching frequency to reduce power loss and increase the power capacity. This increases the delay of the signal sampling and PWM. It also makes the cross-couplings of the d-q current components more severe. In addition, the LCL filter has three cross-coupling loops and is prone to resonance. In order to solve these problems, this paper establishes a complex vector model of an LCL type grid-connected converter. Based on this model, two multiple decoupling current control strategies with passive damping / notch damping are proposed for the LCL type grid-connected converter. The proposed strategies can effectively eliminate the cross-couplings of the converter, achieve independent control of the d-q current components, expand the stable region and suppress the resonance of the LCL filter. Simulation and experimental results verify the correctness of the theoretical analysis and the feasibility of the proposed strategies.

Levosimendan Reduces Lung Injury in a Canine Model of Cardiopulmonary Bypass

Junbo Feng,Haiyuan Liu,Jiayi Chen,Jiyuan Wang,Zhuang Liu,Shenglin Ge 대한심장학회 2016 Korean Circulation Journal Vol.46 No.3

Background and Objectives: To explore the lung-protective effect of levosimendan (LS) during cardiopulmonary bypass in a canine modelby determining the wet/dry weight (W/D) ratio of lung tissue, malonaldehyde (MDA) and superoxide dismutase (SOD) concentrations, andperforming a histological evaluation. Materials and Methods: Thirty-two canines were divided randomly into four groups and underwent a routine aortic cross-clampingcardiopulmonary bypass procedure for 1 h, followed by recovery for 2 h. Animals were handled as follows: group C (means controlgroup), no special treatment after aortic cross clamping; group P (means pulmonary artery perfusion group), pulmonary artery perfusionwith cold oxygenated blood after aortic cross clamping; group LSIV (means intravenous injection of LS group), intravenous injection of LS(65 μg/kg) before thoracotomy, and the rest of the procedure was identical to the control group; group LPS (means pulmonary perfusionwith LS group), pulmonary perfusion with cold oxygenated blood combined with LS (65 μg/kg) after aortic cross clamping. Lung tissueswere removed and subjected to evaluation of pathological alterations, W/D ratio and MDA and SOD concentrations. Results: In group C, the W/D ratio and MDA concentration were higher, while the SOD concentrations were lower (p<0.05). Comparedwith groups P and LSIV, the MDA concentration was lower in group LPS, while that of SOD was higher (p<0.05); Light and electronmicroscopy indicated that LS intervention reduced impairment of lung tissues. Conclusion: Our findings suggest that LS plays an important role in protecting lung tissues.

A dual-site modulated FRET-based two-photon ratiometric fluorescent probe for tracking lysosomal pH changes in living cells, tissues and zebrafish

Zhao, Xiongjie,Wang, Chao,Yuan, Gangqiang,Ding, Haiyuan,Zhou, Liyi,Liu, Xiaogang,Lin, Qinlu Elsevier 2019 Sensors and actuators. B Chemical Vol.290 No.-

<P><B>Abstract</B></P> <P>Lysosomal pH plays an essential role in mediating various biological processes such as immunization, cell metabolism and enzyme activity. Herein, by utilizing the fluorescence resonance energy transfer (FRET) strategy, a two-photon (TP) ratiometric fluorescent probe (NpLys-pH) has been developed for tracking of lysosomal pH changes in living cells, tissues, and zebrafish. NpLys-pH was constructed by conjugating a pH turn-on TP fluorophore <B>1</B> (D-π-A-structured naphthalene derivative) with a pH turn-off naphthalimide fluorophore <B>2</B> <I>via</I> a non-conjugated linker. Meanwhile, NpLys-pH has two potential pH response sites that modulate the fluorescence signal by ICT and PET, respectively. The FRET process exists between the TP fluorophore <B>1</B> and naphthalimide fluorophore <B>2</B>. In addition, NpLys-pH respond to pH rapidly and reversibly with high selectivity and sensitivity and has been applied for tracking lysosomal pH changes in living cells, tissues and zebrafish. We expect that the new probe present here can prompt the development of a wide variety of TP ratiometric fluorescent probes which can find application in detecting other important analytes in biological systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A FRET-based TP ratiometric probe for tracking of lysosome pH changes. </LI> <LI> It has a pH turn-on donor and a pH turn-off acceptor. </LI> <LI> NpLys-pH possesses two well-resolved emission peaks separated by 115 nm. </LI> <LI> It successfully tracked lysosome pH changes in live cells, tissues, and zebrafish. </LI> </UL> </P>

Complex Vector Modeling and Series Decoupling Current Control Strategy of High-Power L/LCL Type Grid-Connected Converter Under Low Switching Frequency

Yingjie Wang,Lanyi Jiao,Bo Yang,Wenchao Wang,Haiyuan Liu 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6

With power level of grid-connected converters rising, the switching frequency of the switching devices is commonly greatly reduced to improve its power capacity. However, this results in serious couplings of the dq current components, which leads to degradation of the static and dynamic performances of grid-connected converters and fluctuations of the reactive power in dynamic processes. In this paper, complex vector models under low switching frequency are established for an L/LCL grid-connected converter, and the relationship between the switching frequency and the coupling degree is analyzed. In addition, a series decoupling current control strategy is put forward. It is shown that the proposed control strategy can eliminate the couplings, improve the performances and have good robustness to parameter variations through static and dynamic characteristics analyses and a sensitivity analysis. Experimental and simulation results also verify the correctness of the theoretical analyses and the superiority of the proposed control strategy.

Complex Vector Modeling and Series Decoupling Current Control Strategy of High-Power L/LCL Type Grid-Connected Converter Under Low Switching Frequency

Wang, Yingjie,Jiao, Lanyi,Yang, Bo,Wang, Wenchao,Liu, Haiyuan The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6

With power level of grid-connected converters rising, the switching frequency of the switching devices is commonly greatly reduced to improve its power capacity. However, this results in serious couplings of the dq current components, which leads to degradation of the static and dynamic performances of grid-connected converters and fluctuations of the reactive power in dynamic processes. In this paper, complex vector models under low switching frequency are established for an L/LCL grid-connected converter, and the relationship between the switching frequency and the coupling degree is analyzed. In addition, a series decoupling current control strategy is put forward. It is shown that the proposed control strategy can eliminate the couplings, improve the performances and have good robustness to parameter variations through static and dynamic characteristics analyses and a sensitivity analysis. Experimental and simulation results also verify the correctness of the theoretical analyses and the superiority of the proposed control strategy.