Line-Interactive UPS for Low-Voltage Microgrids

Zhang, Ping,Cai, Huanyu,Zhao, Hengyang,Shi, Jianjiang,He, Xiangning The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.6

Line-interactive uninterruptible power supply (UPS) systems are good candidates for providing energy storage within a microgrid. In this paper, a control scheme for a line-interactive UPS system applied in a low-voltage microgrid is presented. It is based on the Q-w and P-E droop control to achieve a seamless transition between grid-connected and stand-alone operation modes. Moreover, a new model for designing the controllers is built in the dq-frame based on the instantaneous power definition. The new-built model takes into account the dynamic performance of the output impedance of the inverter in the dq-frame and can be evaluated in the time domain. Compared to the traditional model based on the instantaneous power definition, the new-built model is more accurate to describe the dynamic performance of the system. Simulation and experimental results obtained with a microgrid consisting of two 40-kW line-interactive UPS systems are given to validate the control strategy of the line-active UPS system and the accuracy of the new-built model.

Line-Interactive UPS for Low-Voltage Microgrids

Ping Zhang,Huanyu Cai,Hengyang Zhao,Jianjiang Shi,Xiangning He 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.6

Line-interactive uninterruptible power supply (UPS) systems are good candidates for providing energy storage within a microgrid. In this paper, a control scheme for a line-interactive UPS system applied in a low-voltage microgrid is presented. It is based on the Q-w and P-E droop control to achieve a seamless transition between grid-connected and stand-alone operation modes. Moreover, a new model for designing the controllers is built in the dq-frame based on the instantaneous power definition. The new-built model takes into account the dynamic performance of the output impedance of the inverter in the dq-frame and can be evaluated in the time domain. Compared to the traditional model based on the instantaneous power definition, the new-built model is more accurate to describe the dynamic performance of the system. Simulation and experimental results obtained with a microgrid consisting of two 40-kW line-interactive UPS systems are given to validate the control strategy of the line-active UPS system and the accuracy of the new-built model.

Comparison of Dynamic Characteristics between Virtual Synchronous Machines Adopting Different Active Power Droop Controls

Yuan, Chang,Liu, Chang,Zhang, Xueyin,Zhao, Tianyang,Xiao, Xiangning,Tang, Niang The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3

In modern power systems, high penetration of distributed generators (DGs) results in high stress on system stability. Apart from the intermittent nature of DGs, most DGs do not contribute inertia or damping to systems. As a result, a new control method named virtual synchronous machine (VSM) was proposed, which brought new characteristics to inverters such as synchronous machines (SMs). In addition, different active power droop controls for VSMs are being proposed in literatures. However, they are quite different in terms of their dynamic characteristics despite of the similar control laws. In this paper, mathematical models of a VSM adopting different active power droop controls are built and analyzed. The dynamic performance of the VSM output active power and virtual rotor angular frequency are presented for different models. The influences of the damping factor and droop coefficient on the VSM dynamic behaviors are also investigated in detail. Finally, the theoretical analysis is verified by simulations and experimental results.

Synthesis, Crystal Structure and Fungicidal Activities of New Type Oxazolidinone-Based Strobilurin Analogues

Li, Yuhao,Liu, Rui,Yan, Zhangwei,Zhang, Xiangning,Zhu, Hongjun Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.11

A series of oxazolidinone-based strobilurin analogues were efficiently synthesized by the reaction of 3-(2-bromomethylphenyl) oxazolidin-2-one with 1-substituted phenyl-2H-pyrazolin-3-one. Their structures were confirmed and characterized by $^1H$-NMR, $^{13}C$-NMR, elemental analysis, and mass spectroscopy. In addition, the crystal structure of the target compound 3-(2-((1-phenyl-2H-pyrazol-3-yloxy)methyl)phenyl) oxazolidin-2-one was determined by single crystal X-ray diffraction. The bioassay results of these compounds indicated that some of the oxazolidin-2-one derivatives containing N-substituted phenyl 2H-pyrazol ring exhibited potential in vivo fungicidal activities against M. grisea at the dosage of $1\;g\;L^{-1}$.

Comparison of Dynamic Characteristics between Virtual Synchronous Machines Adopting Different Active Power Droop Controls

Chang Yuan,Chang Liu,Xueyin Zhang,Tianyang Zhao,Xiangning Xiao,Niang Tang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3

In modern power systems, high penetration of distributed generators (DGs) results in high stress on system stability. Apart from the intermittent nature of DGs, most DGs do not contribute inertia or damping to systems. As a result, a new control method named virtual synchronous machine (VSM) was proposed, which brought new characteristics to inverters such as synchronous machines (SMs). In addition, different active power droop controls for VSMs are being proposed in literatures. However, they are quite different in terms of their dynamic characteristics despite of the similar control laws. In this paper, mathematical models of a VSM adopting different active power droop controls are built and analyzed. The dynamic performance of the VSM output active power and virtual rotor angular frequency are presented for different models. The influences of the damping factor and droop coefficient on the VSM dynamic behaviors are also investigated in detail. Finally, the theoretical analysis is verified by simulations and experimental results.

Synthesis, Crystal Structure and Fungicidal Activities of New Type Oxazolidinone-Based Strobilurin Analogues

Yuhao Li,Rui Liu,Zhangwei Yan,Xiangning Zhang,Hongjun Zhu 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.11

A series of oxazolidinone-based strobilurin analogues were efficiently synthesized by the reaction of 3-(2-bromomethylphenyl)oxazolidin-2-one with 1-substituted phenyl-2H-pyrazolin-3-one. Their structures were confirmed and characterized by 1H-NMR, 13C-NMR, elemental analysis, and mass spectroscopy. In addition, the crystal structure of the target compound 3-(2-((1-phenyl-2H-pyrazol-3-yloxy)methyl)phenyl) oxazolidin-2-one was determined by single crystal X-ray diffraction. The bioassay results of these compounds indicated that some of the oxazolidin-2-one derivatives containing N-substituted phenyl 2H-pyrazol ring exhibited potential in vivo fungicidal activities against M. grisea at the dosage of 1 g L‒1.

Bonded-cluster simulation of tool-rock interaction using advanced discrete element method

Weiji Liu,Xiaohua Zhu,Yun-Lai Zhou,Tao Li,Xiangning Zhang 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.4

The understanding of tool-rock interaction mechanism is of high essence for improving the rock breaking efficiency and optimizing the drilling parameters in mechanical rock breaking. In this study, the tool-rock interaction models of indentation and cutting are carried out by employing the discrete element method (DEM) to examine the rock failure modes of various brittleness rocks and critical indentation and cutting depths of the ductile to brittle failure mode transition. The results show that the cluster size and inter-cluster to intra-cluster bond strength ratio are the key factors which influence the UCS magnitude and the UCS to BTS ratio. The UCS to BTS strength ratio can be increased to a more realistic value using clustered rock model so that the characteristics of real rocks can be better represented. The critical indentation and cutting depth decrease with the brittleness of rock increases and the decreasing rate reduces dramatically against the brittleness value. This effort may lead to a better understanding of rock breaking mechanisms in mechanical excavation, and may contribute to the improvement in the design of rock excavation machines and the related parameters determination.