A Bidirectional Dual Buck-Boost Voltage Balancer with Direct Coupling Based on a Burst-Mode Control Scheme for Low-Voltage Bipolar-Type DC Microgrids

Liu, Chuang,Zhu, Dawei,Zhang, Jia,Liu, Haiyang,Cai, Guowei The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.6

DC microgrids are considered as prospective systems because of their easy connection of distributed energy resources (DERs) and electric vehicles (EVs), reduction of conversion loss between dc output sources and loads, lack of reactive power issues, etc. These features make them very suitable for future industrial and commercial buildings' power systems. In addition, the bipolar-type dc system structure is more popular, because it provides two voltage levels for different power converters and loads. To keep voltage balanced in such a dc system, a bidirectional dual buck-boost voltage balancer with direct coupling is introduced based on P-cell and N-cell concepts. This results in greatly enhanced system reliability thanks to no shoot-through problems and lower switching losses with the help of power MOSFETs. In order to increase system efficiency and reliability, a novel burst-mode control strategy is proposed for the dual buck-boost voltage balancer. The basic operating principle, the current relations, and a small-signal model of the voltage balancer are analyzed under the burst-mode control scheme in detail. Finally, simulation experiments are performed and a laboratory unit with a 5kW unbalanced ability is constructed to verify the viability of the bidirectional dual buck-boost voltage balancer under the proposed burst-mode control scheme in low-voltage bipolar-type dc microgrids.

Identification Method of Dangerous Rock Mass on Rock Slope

( Haiyang Liu ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Rockfall is a major threat to projects in mountainous areas, mountain tourist attractions and residents. With the continuous improvement of rockfall risk assessment methods, rockfall hazard and risk are gradually quantificationally assessed. But up to now, no definite method has been put forward for the identification of dangerous rock mass. With the development of unmanned aerial vehicle (UAV) aerial photogrammetry and geographic information system, it is possible to obtain high-precision topographic data and spatial rock mass structure information. In this paper, UAV aerial photogrammetry techniques are used to obtain high-precision topographic data (DTM) and mountain orthophoto data in the research area, and a three-dimensional model of typical slope is established. By delineating the exposed scar, the ultimate stable height of bedrock in this area is determined, and the threshold value can be used to delineate the range of dangerous rock mass. Firstly, the characteristics of rock mass structure in the study area were analyzed, including joint orientations, spacing and density, and the magnitude of rockfall volume was estimated. Secondly, the high-precision DTM data are analyzed to calculate the slope of the connecting plane between the highest point of scar and the lowest point of the side wall, to approximate the original slope of each scar in the research area. Third, the limit height of stable rock mass under different slope is statistically analyzed. Finally, the range of dangerous rock mass is defined by combining the structural information of rock mass and the limit stability height of each slope condition.

A Bidirectional Dual Buck-Boost Voltage Balancer with Direct Coupling Based on a Burst-Mode Control Scheme for Low-Voltage Bipolar-Type DC Microgrids

Chuang Liu,Dawei Zhu,Jia Zhang,Haiyang Liu,Guowei Cai 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.6

DC microgrids are considered as prospective systems because of their easy connection of distributed energy resources (DERs) and electric vehicles (EVs), reduction of conversion loss between dc output sources and loads, lack of reactive power issues, etc. These features make them very suitable for future industrial and commercial buildings’ power systems. In addition, the bipolar-type dc system structure is more popular, because it provides two voltage levels for different power converters and loads. To keep voltage balanced in such a dc system, a bidirectional dual buck-boost voltage balancer with direct coupling is introduced based on P-cell and N-cell concepts. This results in greatly enhanced system reliability thanks to no shoot-through problems and lower switching losses with the help of power MOSFETs. In order to increase system efficiency and reliability, a novel burst-mode control strategy is proposed for the dual buck-boost voltage balancer. The basic operating principle, the current relations, and a small-signal model of the voltage balancer are analyzed under the burst-mode control scheme in detail. Finally, simulation experiments are performed and a laboratory unit with a 5kW unbalanced ability is constructed to verify the viability of the bidirectional dual buck-boost voltage balancer under the proposed burst-mode control scheme in low-voltage bipolar-type dc microgrids.

Complexity Comparison for Drinkers' and Normal People's EEG Using Wavelet Entropy

Jiufu Liu,Lei Gao,Zaihong Zhou,Haiyang Liu,Zhengqian Wang,Wenyuan Liu,Jianyong Zhou 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.8

This paper investigates the influence of alcohol on brain complexity. Considering electro-encephalogram (EEG) has the nonlinear dynamics characteristic of time-varying and non-stationary, we introduce the wavelet entropy (WE) analysis. We denoise EEG signal by using wavelet decomposition, then calculate the wavelet entropy of the denoised signal and analyze the nonlinear complexity. In 64 conductive poles experiments and in different stimulus experiments for FP2 electrode's EEG, the drinkers' EEG wavelet entropy is greater than normal people's. The wavelet entropy of every conductive pole of drinkers’ or normal persons’ is inconformity.

Spectrum Cartography Based on Dynamic Compressed Sensing by Using Multiple Domains Information

Xia, Haiyang,Huang, Jijun,Liu, Jibin,Liu, Peiguo,Zha, Song 한국통신학회 2023 Journal of communications and networks Vol.25 No.4

Radio maps have experienced their success in ap-plications of wireless communications for years by offeringmetrics of radio frequency (RF) information, e.g., power spectraldensity (PSD), within a geographical region of interest. Spectrumcartography technique constructs radio maps to expand theabilities of RF awareness. However, seldom of existing methodsaim at constructing radio maps by utilizing multiple domains in-formation. In this paper, a novel framework inspired by dynamiccompressed sensing (DCS) has been proposed firstly to solve thisproblem. This flexible framework first to apply joint group-Lassofor PSD map construction based on the different sparse patternsbetween space and frequency domains as well as innovativelyutilizes transmitters’ mobility patterns for support prediction ofDCS. Simulation experiments have been processed to assess theperformance of methods within the proposed framework andframework’s superiority has been proven.

Study on Preparation and Properties of PAI Materials Containing Trifluoromethyl in Side Chain

Haiyang Yang,Duxin Li,Jun Yang,Jin Wang,Shunchang Gan,Kaikai Cao,Yufeng Liu 한국고분자학회 2021 Macromolecular Research Vol.29 No.10

Polyamide-imide (PAI) materials with good heat resistance, excellent friction, wear properties, and low water absorption were prepared by acyl chloride process with diamine monomer containing trifluoromethyl in the side chain. The results showed that PAI prepared from 2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]- 4,4'-diamine without flexible hinge group had the best heat resistance, with T g as high as 302.6℃ and T d5% as 490.1℃. With the increase of the proportion of flexible hinge groups in diamine monomer, the thermal properties of PAI materials would decrease. The wear mechanism of PAI prepared from 2,2'-bis(trifluoromethyl)- [1,1'-biphenyl]-4,4'-diamine was mainly adhesive wear. With the increase of the proportion of flexible hinge groups in diamine monomer, the wear mechanism would change from abrasive wear, slight adhesive wear to severe adhesive wear. The friction coefficient and wear loss of PAI prepared by 1,4-bis(4-amino-2-trifluoromethylphenoxy) benzene were the smallest, which were 0.4706 and 3.5, respectively. PAI synthesized by diamine monomer containing trifluoromethyl had low water absorption and high water contact angle. With the increasing flexibility of monomer containing trifluoromethyl diamine, the elongation at break and tensile strength of the material increased gradually.

Experimental Study on Bond Behavior between Section Steel and RAC under Full Replacement Ratio

Chao Liu,Ziyu Fan,Xiaona Chen,Chao Zhu,Haiyang Wang,Guoliang Bai 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.3

Nine specimens of steel reinforced recycled concrete are designed to explore the effect of four factors as the cover thickness of section steel, the embedded length of section steel, the recycled aggregate concrete strength, and the lateral stirrup ratio on bond slip between section steel and recycled aggregate concrete. The test results show that the failure modes of recycled aggregate concrete are as similar as normal concrete; three formulas are proposed for the bond stress between section steel and recycled aggregate concrete, which are fitting well. The mathematical model of bond stress-slip is established through analysis, and the predicted curve is close to the test curve. The research results provide the basis for the numerical simulation analysis of the bond slip for the recycled aggregate concrete under the full replacement ratio.

Point reconstruction for differential mesh deformation

Hua Liu,Hongxin Zhang,Haiyang Jiang,Hujun Bao (사)한국CDE학회 2007 한국CAD/CAM학회 국제학술발표 논문집 Vol.2007 No.8

Thermodynamic analysis of a novel adiabatic compressed air energy storage system with water cycle

Zhen Xu,Haiyang Yang,Yingchun Xie,Jinchi Zhu,Chaoqun Liu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.6

A novel water cycle compressed air energy storage system (WC-CAES) is proposed to improve the energy storage density (ESD) and round trip efficiency (RTE) of A-CAES. The new system decreases electricity consumption by recovering and reusing the hydraulic pressure of water. The thermodynamic characteristics of WC-CAES are evaluated by energy and advanced exergy analysis method. When the air storage pressure of WC-CAES is equal to the minimum storage pressure of A-CAES (4.2 MPa), the ESD and generalized storage density increase by 5.85 % and 32.41 %, respectively. When the air storage pressure increases to the same level as A-CAES (7.2 MPa), ESD and generalized storage density increase by 112 % and 162 %, respectively. In addition, the RTE increases by 1.6 % when the air storage pressure is 4.2 MPa. WC-CAES is therefore verified to be an effective way to improve the performance of conventional A-CAES.

H∞ Synchronization of Two Different Discrete-Time Chaotic Systems via a Unified Model

Mei-Qin Liu,Haiyang Chen,Senlin Zhang,Weihua Sheng 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.1

This paper presents some novel synchronization methods for two discrete-time chaotic systems with different time delays, which are transformed into two unified models. First, the H∞ performance of the synchronization error dynamical system between the drive unified model and the response one is analyzed using the linear matrix inequality (LMI) approach. Second, the novel state feedback controllers are established to guarantee H∞ performance for the overall system. The parameters of these controllers are determined by solving the eigenvalue problem (EVP). Most discrete-time chaotic systems with or without time delays can be converted into this unified model, and H∞ synchronization controllers are designed in a unified way. The effectiveness of the proposed design methods are demonstrated by three numerical examples.