A Fast-Transient Repetitive Control Strategy for Programmable Harmonic Current Source

Wanjun Lei,Cheng Nie,Mingfeng Chen,Huajia Wang,Yue Wang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

The repetitive control (RC) strategy is widely used in AC power systems because of its high performance in tracking period signal and suppressing steady-state error. However, the dynamic response of RC is determined by the fundamental period delay T0 existing in the internal model. In the current study, a (nk ± i)-order harmonic RC structure is proposed to improve dynamic performance. The proposed structure has less data memory and can improve the tracking speed by n/2 times. T0 proves the effectiveness of the (nk ± i)-order RC strategy. The simulation and experiments of (6k ± 1)-order and (4k ± 1)-order RC strategy used in the voltage source inverter is conducted in this study to control the harmonic current source, which shows the validity and advantages of the proposed structure.

A Fast-Transient Repetitive Control Strategy for Programmable Harmonic Current Source

Lei, Wanjun,Nie, Cheng,Chen, Mingfeng,Wang, Huajia,Wang, Yue The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

The repetitive control (RC) strategy is widely used in AC power systems because of its high performance in tracking period signal and suppressing steady-state error. However, the dynamic response of RC is determined by the fundamental period delay $T_0$ existing in the internal model. In the current study, a ($nk{\pm}i$)-order harmonic RC structure is proposed to improve dynamic performance. The proposed structure has less data memory and can improve the tracking speed by n/2 times. $T_0$ proves the effectiveness of the ($nk{\pm}i$)-order RC strategy. The simulation and experiments of ($6k{\pm}1$)-order and ($4k{\pm}1$)-order RC strategy used in the voltage source inverter is conducted in this study to control the harmonic current source, which shows the validity and advantages of the proposed structure.

Preparation of γ-alumina nanoparticle modified polyacrylamide composite and study on its solid phase extraction of Sunset Yellow

Wanjun Li,Qiong Jia,Zhenyu Zhang,Yuanpeng Wang 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.4

An organic-inorganic composite, γ-alumina nanoparticle modified polyacrylamide, was synthesized in this study. The composite was characterized by scanning electron microscope, nitrogen adsorption-desorption measurement, thermal gravimetric analyzer, differential scanning calorimetry, and Fourier-transformed infrared spectrometer. A novel solid-phase extraction method with the synthesized composite as the adsorbent was developed for the enrichment of Sunset Yellow coupled with ultraviolet-visible spectrophotometry. To obtain the optimum extraction efficiency, the experimental parameters in the processes of preparation of the adsorbent and solid-phase extraction were studied including synthesis temperature, synthesis time, the dosage of γ-alumina nanoparticles, sample flow rate, sample pH, eluant concentration, and eluant flow rate. Under the optimum conditions, the detection limit of the developed method was calculated to be 0.037 μg mL−1 with intra-day and inter-day relative standard deviation values of 2.57% and 3.89%, respectively. When the method was applied to the determination of Sunset Yellow in beverages, satisfactory recoveries were obtained in the range of 92.3-109.8%.

Modeling and Analysis of Harmonic Resonance in Microgrid and Research of Active Harmonic Resistance Method

Cheng Nie,Wanjun Lei,Huajia Wang,Kai Zhang,Yue Wang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

In the microgrid, the capacitive element such as compensation capacitor may resonance with the line inductance in harmonic frequency, furthermore serious harmonic resonance may endanger the system. In this paper, resonance mode analysis (RMA) method is used to analysis the harmonic resonance in the microgrid. To suppress the amplified of harmonic current near resonance frequency, an improved current control method for active harmonic resistance (AHR) is proposed. Simulation and experimental results reveal that the proposed method can suppress the resonance in the microgrid effectively.

Novel Carrier-Based PWM Strategy of a Three-Level NPC Voltage Source Converter without Low-Frequency Voltage Oscillation in the Neutral Point

Li, Ning,Wang, Yue,Lei, Wanjun,Niu, Ruigen,Wang, Zhao'an The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.3

A novel carrier-based PWM (CBPWM) strategy of a three-level NPC converter is proposed in this paper. The novel strategy can eliminate the low-frequency neutral point (NP) voltage oscillation under the entire modulation index and full power factor. The basic principle of the novel strategy is introduced. The internal modulation wave relationship between the novel CBPWM strategy and traditional SPWM strategy is also studied. All 64 modulation wave solutions of the CBPWM strategy are derived. Furthermore, the proposed CBPWM strategy is compared with traditional SPWM strategy regarding the output phase voltage THD characteristics, DC voltage utilization ratio, and device switching losses. Comparison results show that the proposed strategy does not cause NP voltage oscillation. As a result, no low-frequency harmonics occur on output line-to-line voltage and phase current. The novel strategy also has higher DC voltage utilization ratio (15.47% higher than that of SPWM strategy), whereas it causes larger device switching losses (4/3 times of SPWM strategy). The effectiveness of the proposed modulation strategy is verified by simulation and experiment results.

Research on Multi-frequency Current Tracking Control of Three-phase Grid-connected VSI

Chongfu XU,Wanjun LEI,Gaidi NING,Xiang ZHANG,Yue WANG,Jinjun LIU 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

This paper proposes a multi-frequency current tracking control method which can be applied in the application of APF(Active Power Filter), programmable current source etc. Because the method based on the stationary PI inner loop and the dq outer loop can’t be used in the case of high frequency, a new method is proposed. The proposed method includes a stationary PI inner loop and an Amplitude-Phase outer loop, which can realize separate control of each harmonic in each phase precisely in a wide frequency range, and keep the advantages of the stationary PI method: the anti-interference ability, low harmonic distortion in the line current, fast response speed and simple control. The parameter design method of both loops is also described. At last, simulation results based on PSCAD/EMTDC and experimental results are given to prove the feasibility of this method.

Research on Hybrid Dynamic Capacitor-a novel approach to VAR compensation and resonance suppression

Zhang Kai,Lei Wanjun,Cheng Nie,Yue Wang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

In this paper, a control method named hybrid dynamic capacitor is proposed to provide dynamic VAR compensation and suppress resonance between power capacitor and system inductance in power distribution network. This paper explains the theory of hybrid dynamic capacitor and this method benefits by reducing the initial cost, switching loss and less harmonic current. Finally, simulation and experiment results are given to verify the viability and effectiveness of the hybrid dynamic capacitor and its compensation characteristic.

FSSPCM: Fuzzy Publication of Data for Privacy Preserving

Yan Yan,Xiaohong Hao,Wanjun Wang 보안공학연구지원센터 2016 International Journal of Security and Its Applicat Vol.10 No.11

The rapid development of information technology makes it convenient to release, collect, store and analyze various types of data. At the same time, how to protect the privacy of individual and prevent disclosure of sensitive information during data publication has become a major challenge. K-anonymity method is the most widely used privacy protection model and has been well researched. However, generalization and suppression operations used in K-anonymity methods require high computational effort and cause excessive loss of original information, which will greatly reduce the availability of data after publishing. The paper proposed a transformation algorithm for privacy preserving data publishing based on fuzzy semantic set pair cloud model (FSSPCM). It transforms the sensitive attributes into the form of fuzzy semantic values, and privacy of individual has been maintained because exact values cannot be predicted after data publishing. In order to enhance the availability of data after publishing, semantic distinction (SD) and reserve degree (RD) are designed to reflect relationships between original data and fuzzy semantic information after transformation according to different characteristics of numerical sensitive attributes and categorical sensitive attributes. Experiments and analysis demonstrate the effectiveness of the proposed method both on numerical and categorical sensitive attributes. Classification performed on original and transformed information proves the proposed method maintains higher clustering similarity after fuzzy transformation, which will provide better availability for data mining and other processing.

Novel Carrier-Based PWM Strategy of a Three-Level NPC Voltage Source Converter withoutLow-Frequency Voltage Oscillation in the Neutral Point

Ning Li,Yue Wang,Wanjun Lei,Ruigen Niu,Zhao’an Wang 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.3

A novel carrier-based PWM (CBPWM) strategy of a three-level NPC converter is proposed in this paper. The novel strategy can eliminate the low-frequency neutral point (NP) voltage oscillation under the entire modulation index and full power factor. The basic principle of the novel strategy is introduced. The internal modulation wave relationship between the novel CBPWM strategy and traditional SPWM strategy is also studied. All 64 modulation wave solutions of the CBPWM strategy are derived. Furthermore, the proposed CBPWM strategy is compared with traditional SPWM strategy regarding the output phase voltage THD characteristics, DC voltage utilization ratio, and device switching losses. Comparison results show that the proposed strategy does not cause NP voltage oscillation. As a result, no low-frequency harmonics occur on output line-to-line voltage and phase current. The novel strategy also has higher DC voltage utilization ratio (15.47% higher than that of SPWM strategy), whereas it causes larger device switching losses (4/3 times of SPWM strategy). The effectiveness of the proposed modulation strategy is verified by simulation and experiment results.

Enhanced photocatalytic mechanism of Ag₃PO₄ nano-sheets using MS₂ (M = Mo, W)/rGO hybrids as co-catalysts for 4-nitrophenol degradation in water

Zhang, Weiping,Li, Guiying,Wang, Wanjun,Qin, Yaxin,An, Taicheng,Xiao, Xinyan,Choi, Wonyong Elsevier 2018 Applied Catalysis B Vol.232 No.-

<P><B>Abstract</B></P> <P>A chemically modified Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>(M = Mo, W)/rGO composite was firstly synthesized via a liquid-exfoliation solvothermal method. The structure, morphology, optical properties and composition were characterized by X-ray diffraction, FT-IR spectroscopy, scanning electron microscopy, UV–vis diffuse reflectance spectra and X-ray photoelectron spectroscopy, respectively. The characterization results indicated that compact structure could be obtained by using this typical method due to in-situ chemical modification, which could also control the sizes of Ag<SUB>3</SUB>PO<SUB>4</SUB> nano-sheets by adding MS<SUB>2</SUB>/rGO hybrids. More importantly, the resultant Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO composite exhibited higher photocatalytic activity and stability toward the degradation of 4-nitrophenol than pure Ag<SUB>3</SUB>PO<SUB>4</SUB> under sunlight irradiation. The stable structure of Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO was closely related with Z-scheme electronic structure and electrical conductivity of MS<SUB>2</SUB>/rGO hybrids, leading to a higher consumption and transfer of photogenerated electrons. However, by controlling the amounts of MS<SUB>2</SUB>/rGO hybrids, more stable but lower photocatalytic activity composites could be obtained. Further analysis found that the holes and O<SUB>2</SUB> <SUP>−</SUP> were the main reactive species involved in the photocatalytic degradation of 4-nitrophenol. In addition, possible photocatalytic degradation pathways of 4-nitrophenol were also proposed based on the identified intermediates. The findings of this work may provide a new method to design efficient composites for photocatalytic degradation of organic pollutants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO catalyst was fabricated via a liquid-exfoliation solvothermal method. </LI> <LI> Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO has high photocatalytic activity and stability under sunlight. </LI> <LI> The stability of Ag<SUB>3</SUB>PO<SUB>4</SUB>@MS<SUB>2</SUB>/rGO was due to its rapid transfer of photogenerated e<SUP>−</SUP>. </LI> <LI> h<SUP>+</SUP> and O<SUB>2</SUB> <SUP>−</SUP> were the main RSs in photocatalytic degradation of 4-nitrophenol. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>