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
In consensus building process in medicine, it is said that it is crucial for its participants to understand why each stakeholder, patient, his/her family, physician, nurse, etc., in decision-making has his/her own opi...In consensus building process in medicine, it is said that it is crucial for its participants to understand why each stakeholder, patient, his/her family, physician, nurse, etc., in decision-making has his/her own opinion. In order to understand this condition more deeply, I develop the notion of ＂reason of opinion＂ to characterize the process as ＂prospective consensus building.＂ This prospective consensus building should satisfy the requirements of having ＂history of reason＂ and ＂list of risks.＂ The former requirement, history of reason, can be characterized by making clear when one started to form the reason of an opinion, how one formed the reason, what kind of relationship is supposed to be between the present opinion and its reason, and what kind of result is expected to come out after a decision making. The latter requirement, the list of risks, should display what kind of outcomes are supposed to come out in each alternative of the decision making. Prospective consensus building makes it possible, firstly, for the stakeholders to understand the patient＇s needs more deeply. For the patient, secondly, the each stakeholder would be able to become aware of his/her own sense of value and to confirm what he/she expects from the result of his/her decision-making. For all the stakeholders, thirdly, it would make it possible to decrease the amount of risks of misunderstanding and to share their expectations for their well-being. Finally, the stakeholders can reach a satisfactory consensus and find a way to the better solution.展开更多
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.
文摘In consensus building process in medicine, it is said that it is crucial for its participants to understand why each stakeholder, patient, his/her family, physician, nurse, etc., in decision-making has his/her own opinion. In order to understand this condition more deeply, I develop the notion of ＂reason of opinion＂ to characterize the process as ＂prospective consensus building.＂ This prospective consensus building should satisfy the requirements of having ＂history of reason＂ and ＂list of risks.＂ The former requirement, history of reason, can be characterized by making clear when one started to form the reason of an opinion, how one formed the reason, what kind of relationship is supposed to be between the present opinion and its reason, and what kind of result is expected to come out after a decision making. The latter requirement, the list of risks, should display what kind of outcomes are supposed to come out in each alternative of the decision making. Prospective consensus building makes it possible, firstly, for the stakeholders to understand the patient＇s needs more deeply. For the patient, secondly, the each stakeholder would be able to become aware of his/her own sense of value and to confirm what he/she expects from the result of his/her decision-making. For all the stakeholders, thirdly, it would make it possible to decrease the amount of risks of misunderstanding and to share their expectations for their well-being. Finally, the stakeholders can reach a satisfactory consensus and find a way to the better solution.
