Due to the rapid economic and social development, the quality of life of people has been significantly improved, and peopled demand for living environment has become increasingjy high, which has increased peop...Due to the rapid economic and social development, the quality of life of people has been significantly improved, and peopled demand for living environment has become increasingjy high, which has increased peopled awareness of landscaping. Because of the development of urbankation, however, most cities have lost their balance in the ecological enviionment although they seem to have the modem flavor of life. Integrating garden design with plant protection is an important measure to protect the ecological environment and maintain ecological balance. How to protect the plants in urban garden planning and design has become a problem to be solved by garden designers. In this paper, the relationship between garden design and plant protection was ekbofated, the status quo and problems of ornamental plant protection were analyzed, and measures to protect ornamental plants were proposed.展开更多
Micro-grids comprise low voltage distribution systems with distributed energy resources(DERs) and controllable loads which can operate connected to the medium voltage grid or islanded in a controlled coordinated way. ...Micro-grids comprise low voltage distribution systems with distributed energy resources(DERs) and controllable loads which can operate connected to the medium voltage grid or islanded in a controlled coordinated way. This concept aims to move from "connect and forget" philosophy towards a full integration of DERs. Micro-grids can provide numerous economic and environmental benefits for end-customers, utilities and society. However, their implementation poses great technical challenges, such as a new philosophy in design of protection systems. In this work, a micro-grid protection scheme is presented based on positive-sequence component using phasor measurement units(PMUs) and a central protection unit(CPU). The salient feature of the proposed scheme in comparison with the previous works is that it has the ability to protect both radial and looped micro-grids against different types of faults with the capability of single-phase tripping. Furthermore, since the CPU is capable of updating its pickup values(upstream and downstream equivalent positive-sequence impedances of each line) after the first change in the micro-grid configuration(such as transferring from grid-connected to islanded mode and or disconnection of a line, bus, or DER either in grid-connected mode or in islanded mode), it can protect micro-grid against subsequent faults. Finally, in order to verify the effectiveness of the suggested scheme and the CPU, several simulations have been undertaken by using DIg SILENT Power Factory and MATLAB software packages.展开更多
文摘Due to the rapid economic and social development, the quality of life of people has been significantly improved, and peopled demand for living environment has become increasingjy high, which has increased peopled awareness of landscaping. Because of the development of urbankation, however, most cities have lost their balance in the ecological enviionment although they seem to have the modem flavor of life. Integrating garden design with plant protection is an important measure to protect the ecological environment and maintain ecological balance. How to protect the plants in urban garden planning and design has become a problem to be solved by garden designers. In this paper, the relationship between garden design and plant protection was ekbofated, the status quo and problems of ornamental plant protection were analyzed, and measures to protect ornamental plants were proposed.
文摘Micro-grids comprise low voltage distribution systems with distributed energy resources(DERs) and controllable loads which can operate connected to the medium voltage grid or islanded in a controlled coordinated way. This concept aims to move from "connect and forget" philosophy towards a full integration of DERs. Micro-grids can provide numerous economic and environmental benefits for end-customers, utilities and society. However, their implementation poses great technical challenges, such as a new philosophy in design of protection systems. In this work, a micro-grid protection scheme is presented based on positive-sequence component using phasor measurement units(PMUs) and a central protection unit(CPU). The salient feature of the proposed scheme in comparison with the previous works is that it has the ability to protect both radial and looped micro-grids against different types of faults with the capability of single-phase tripping. Furthermore, since the CPU is capable of updating its pickup values(upstream and downstream equivalent positive-sequence impedances of each line) after the first change in the micro-grid configuration(such as transferring from grid-connected to islanded mode and or disconnection of a line, bus, or DER either in grid-connected mode or in islanded mode), it can protect micro-grid against subsequent faults. Finally, in order to verify the effectiveness of the suggested scheme and the CPU, several simulations have been undertaken by using DIg SILENT Power Factory and MATLAB software packages.
