Experimental investigation on the propagation characteristics of pressure oscillation in direct contact condensation with low mass flux steam jet

Qiu, Binbin,Yang, Qingchuan,Yan, Junjie,li, Gen,Revankar, Shripad T. Elsevier 2017 Experimental thermal and fluid science Vol.88 No.-

<P><B>Abstract</B></P> <P>The propagation characteristics of pressure oscillation in direct contact condensation with low mass flux steam jet have been investigated experimentally. Steam is injected into subcooled water at one atmosphere pressure with steam mass flux and water temperature range of 186–272kg/(m<SUP>2</SUP> s) and 293–343K. The pressure oscillation propagates in the form of wave with stable dominant frequency, however the wave intensity attenuates with the increasing distance from the oscillation source. The root mean square of pressure wave <I>p</I> <SUB>rms</SUB> attenuates rapidly with the increasing dimensionless radial distance from the nozzle exit. At about dimensionless radial distance <I>R</I> =100, the <I>p</I> <SUB>rms</SUB> is attenuated by about 90%. Although the dominant frequency of the pressure oscillation is constant during the propagation, after <I>R</I> =100, there will be not enough energy for the pressure oscillation to resonate with relevant equipment. A correlation equation to calculate the root mean square of pressure oscillation along the radial distance is given. The prediction errors are within ±30% compared with the experimental data.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The pressure oscillation propagates in the form of wave. </LI> <LI> In the propagation process, the frequency remains the same but the intensity attenuates. </LI> <LI> A correlation to calculate the <I>p</I> <SUB>rms</SUB> along the radial distance is given. </LI> <LI> At about R=100, the <I>p</I> <SUB>rms</SUB> is attenuated by about 90% and most of the energy is dissipated. </LI> </UL> </P>

Circulating Current Harmonics Suppression for Modular Multilevel Converters Based on Repetitive Control

Li, Binbin,Xu, Dandan,Xu, Dianguo The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6

Modular multilevel converters (MMCs) have emerged as the most promising topology for high and medium voltage applications for the coming years. However, one particular negative characteristic of MMCs is the existence of circulating current, which contains a dc component and a series of low-frequency even-order ac harmonics. If not suppressed, these ac harmonics will distort the arm currents, increase the power loses, and cause higher current stresses on the semiconductor devices. Repetitive control (RC) is well known due to its distinctive capabilities in tracking periodic signals and eliminating periodic errors. In this paper, a novel circulating current control scheme base on RC is proposed to effectively track the dc component and to restrain the low-frequency ac harmonics. The integrating function is inherently embedded in the RC controller. Therefore, the proposed circulating current control only parallels the RC controller with a proportional controller. Thus, conflicts between the RC controller and the traditional proportional integral (PI) controller can be avoided. The design methodologies of the RC controller and a stability analysis are also introduced. The validity of the proposed circulating current control approach has been verified by simulation and experimental results based on a three-phase MMC downscaled prototype.

Analysis of the Operating Principle and Parameter Design for the Modular Multilevel DC/DC Converter

Binbin Li,Shaolei Shi,Yibo Zhang,Rongfeng Yang,Gaolin Wang,Dianguo Xu 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

The modular multilevel converter (MMC) has become more and more attractive in the field of high-voltage high-power dc/ac power conversions. In the very recent years, the dc/dc modular multilevel converter is proposed intended for high-voltage dc/dc applications, such as the solid-state transformers and future dc-grid networks, which is extended from the traditional MMC. However, it remains unknown how to optimize the operation of this dc/dc modular multilevel converter and how to dimension the parameters of the elements in it. In this paper, a detailed analysis is performed to indentify the operating principle of the dc/dc modular multilevel converter. Using these analyses, the selection rules and parameter design method of the components are given to maximize the utilization ratio, improve the power density, and increase efficiency. Finally, the validity and effectiveness of this paper are verified by simulation results.

Circulating Current Harmonics Suppression for Modular Multilevel Converters Based on Repetitive Control

Binbin Li,Dandan Xu,Dianguo Xu 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6

Modular multilevel converters (MMCs) have emerged as the most promising topology for high and medium voltage applications for the coming years. However, one particular negative characteristic of MMCs is the existence of circulating current, which contains a dc component and a series of low-frequency even-order ac harmonics. If not suppressed, these ac harmonics will distort the arm currents, increase the power loses, and cause higher current stresses on the semiconductor devices. Repetitive control (RC) is well known due to its distinctive capabilities in tracking periodic signals and eliminating periodic errors. In this paper, a novel circulating current control scheme base on RC is proposed to effectively track the dc component and to restrain the low-frequency ac harmonics. The integrating function is inherently embedded in the RC controller. Therefore, the proposed circulating current control only parallels the RC controller with a proportional controller. Thus, conflicts between the RC controller and the traditional proportional integral (PI) controller can be avoided. The design methodologies of the RC controller and a stability analysis are also introduced. The validity of the proposed circulating current control approach has been verified by simulation and experimental results based on a three-phase MMC downscaled prototype.

Modulation, Harmonic Analysis, and Balancing Control for a New Modular Multilevel Converter

Binbin Li,Yi Zhang,Gaolin Wang,Dianguo Xu 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

The modular multilevel converter (MMC) has been receiving increased attentions in recent years. The new modular multilevel converter is a derivative topology from the traditional MMC in which the number of sub-modules (SMs) necessitated by each phase can be reduced by one. This paper presents a phase-shifted carrier pulse-width modulation (PSC-PWM) for the new MMC with an optimal phase-shifted angle to suppress the harmonics of the output voltage. Further, the harmonic features when the capacitor voltage of the middle SM is selected as two different values are also investigated. Moreover, in order to avoid introducing an unnecessary dc offset current at the ac terminals of the new MMC, a novel capacitor voltage balancing scheme is proposed by adjusting the amplitude of the reference signals rather than the offset. Finally, the validity and effectiveness of the proposed modulation and balancing schemes have been verified by experimental results based on a three-phase prototype of the new MMC.

An IGBT Open-Circuit Fault Detection Method for Modular Multilevel Converters

Binbin Li,Yi Zhang,Rongfeng Yang,Gaolin Wang,Dianguo Xu 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Recently, the modular multilevel converter (MMC) has attracted increasing attentions due to its distinctive features, especially in the application of HVDC power transmission. One of the most significant characteristic of MMC is that it is composed of identical low-voltage submodules (SMs). As a result, the low-voltage IGBTs can be employed in each SM as the main power switch. However, since an MMC station usually contains hundreds of SMs, the IGBT becomes the most fragile component. In this paper, the failure characteristics of the IGBT open-circuit fault in a SM are firstly analyzed. Then, an observer-based IGBT open-circuit detection method is proposed, which can accurately detect the fault by comparing the estimated values with the actual sampled values. Finally, the validity and effectiveness of the proposed fault detection method are demonstrated by experimental results based on a single-phase MMC prototype in the laboratory.

Modulation, Harmonic Analysis, and Balancing Control for a New Modular Multilevel Converter

Li, Binbin,Zhang, Yi,Wang, Gaolin,Xu, Dianguo The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

The modular multilevel converter (MMC) has been receiving increased attentions in recent years. The new modular multilevel converter is a derivative topology from the traditional MMC in which the number of sub-modules (SMs) necessitated by each phase can be reduced by one. This paper presents a phase-shifted carrier pulse-width modulation (PSC-PWM) for the new MMC with an optimal phase-shifted angle to suppress the harmonics of the output voltage. Further, the harmonic features when the capacitor voltage of the middle SM is selected as two different values are also investigated. Moreover, in order to avoid introducing an unnecessary dc offset current at the ac terminals of the new MMC, a novel capacitor voltage balancing scheme is proposed by adjusting the amplitude of the reference signals rather than the offset. Finally, the validity and effectiveness of the proposed modulation and balancing schemes have been verified by experimental results based on a three-phase prototype of the new MMC.

Parallel Point-multiplication based on the Extended Basic Operations on Conic Curves over Ring Zn

Yongnan Li,Limin Xiao,Siming Chen,Hongyun Tian,Li Ruan,Binbin Yu 한국정보기술융합학회 2011 JoC Vol.2 No.1

청말·민국 시기 중국 지리교과서에 나타난 한국 인식의 변화

이빈빈 ( Li Binbin ) 한국정치사회연구소 2023 한국과 국제사회 Vol.7 No.6

청말·민국 시기 중국 지리교과서는 한국 관련 서술이 풍부하여 당시 중국인들이 한국을 어떻게 인식했는지 연구하는 데 유용한 공적 자료이다. 한·중 양국은 수천 년 동안 정치, 경제, 문화 등 많은 방면에서 교류했으며, 19세기 말 이전까지 한국은 중국 주도 하의 중화질서에서 가장 중요한 일원으로서 중국의 전통 지리 문헌에서 항상 ‘소중화’와 ‘예의지방’으로 높은 명성을 누렸다. 그러나 20세기 들어 중국 지리교과서 속 한국의 이미지는 이전과는 확연히 달라졌다. 본 논문은 청말·민국 시기 중국의 교육 근대화 이후 편찬된 일련의 신식 지리교과서에 나타난 한국의 개화기 및 일제강점기 관련 서술과 인식을 비교연구로 하였다. 19세기 말 이후 한·중 양국 관계는 불평등에서 평등으로, 상하급에서 동반자로 전환되었고 이에 따라 청말·민국시기 중국 지리교과서에 나타난 한국의 이미지도 대체로 ‘소중화’에서 ‘후진국’으로, 그리고 다시 ‘동반자’로 바뀌는 과정을 거쳤다. 중국 지리교과서 속 한국의 이미지는 시기별로 중국이 직면한 여러 가지 현실적인 곤경에 영향을 받아 변화해 왔다. 대중의 지리 지식과 타국 인식을 양성하는 주요 매체인 지리교과서에 대한 연구를 통해 당시 중국 정부와 교과서 편찬자가 자라나는 후속세대에게 한국을 어떻게 인식시키려고 했는지를 살펴보았다. 그리고 견문록, 신문잡지 등 사적 자료를 연구 내용으로 한 기존의 선행 연구와 상호 검증과 보완의 관계를 형성할 수 있기를 기대한다. The geography textbooks of the late Qing Dynasty and the Republic of China contained quite rich descriptions of Korea, which were very powerful materials for studying the Chinese people’s knowing of Korea at that time. Before the end of the 19th century, Korea, as the most important member of the China Order, had always enjoyed the reputation of 'Sojunghwa' and 'Polite Country' in traditional Chinese classics. However, since the beginning of the 20th century, the image of Korea in geography textbooks has undergone great changes compared with before. Since the end of the 19th century, relations between Korea and China have shifted from inequality to equality, from upper and lower levels to partners, and as a result, Korea's image in Chinese geography textbooks during the late Qing Dynasty and the Republic of China periods, and has roughly experienced the process of changing from 'Sojunghwa' to 'Backward Country' and finally to 'Companion'. Korea's image in Chinese geography textbooks has changed under the influence of various realistic difficulties facing China over time.

A conserved oligomeric Golgi complex component-related protein is essential for pollen development in Arabidopsis

Tien Dung Nguyen,Binbin Li,Sung Aeong Oh,Soon Ki Park 한국육종학회 2015 한국육종학회 심포지엄 Vol.2015 No.07

To identify genes that play critical roles during male gametogenesis in Arabidopsis, we have isolated several pollen morphological mutants from a mutagenized seed pool generated with a T-DNA activation vector. In this study, we have focused on a mutant plant producing ~50% abnormal pollen grains including high levels of collapsed pollen at maturity. The pollen developmental analysis showed that the mutant pollen phenotype was first observed at tricellular stage. Interestingly, the mutation was only maintained as a heterozygote due to the severely reduced genetic transmission through both sexes. TAIL PCR analysis led to the identification of the responsible gene which encodes a conserved oligomeric golgi complex component-related protein (COGCC). RT-PCR analysis showed predominant expression of the gene in reproductive organs including developing spores. The gene identity was confirmed by the result that mutant plants harboring a T-DNA containing corresponding wild type gene produced less level of mutant pollen grains. Furthermore, confocal laser scanning microscopy using mature pollen expressing COGCC-RFP driven under the native promoter showed small punctate signals, which are likely to be from the Golgi complex. Further experiments for co-localization of the COGCC-RFP with the Golgi markers are underway.