A few multi-terminal direct current(MTDC)systems are in operation around the world today. However,MTDC grids overlaying their AC counterpart might a reality in a near future. The main drivers for constructing such dir...A few multi-terminal direct current(MTDC)systems are in operation around the world today. However,MTDC grids overlaying their AC counterpart might a reality in a near future. The main drivers for constructing such direct current grids are the large-scale integration of remote renewable energy resources into the existing alternative current(AC) grids, and the promotion and development of international energy markets through the socalled supergrids. This paper presents the most critical challenges and prospects for such emerging MTDC grids,along with a foreseeable technology development roadmap,with a particular focus on crucial control and operational issues that are associated with MTDC systems and grids.展开更多
Here,using the probabilistic evaluation based on the Monte Carlo method,back-flashover rate and shielding failure flashover rate of 230 kV overhead transmission lines in the western regions of Iran are evaluated.To su...Here,using the probabilistic evaluation based on the Monte Carlo method,back-flashover rate and shielding failure flashover rate of 230 kV overhead transmission lines in the western regions of Iran are evaluated.To such an aim,first,the number of thunderstorm days per year is collected from the reported weather information in order to determine the ground flash density.Then,using MRU-200 equipment,the tower-footing resistance of several towers is measured.Matlab®software is used in order to produce lightning surges considering its probabilistic nature and randomly distribution on the ground to evaluate striking distance based on the geometric model.Then,calculated parameters are transferred to EMTP-RV software by establishing a link to perform the transient simulation and report the results for modelled 230 kV transmission line.Finally,considering IEEE-1243 standard,it is shown that due to high ground flash density,using 230 kV tower with one shield wire is not sufficient to protect the line against lightning phenomena.展开更多
Interconnections between AC power systems,power transmission with higher efficiency,and aggregation and delivery of power from offshore wind farms to different AC regions are among the main drivers for the development...Interconnections between AC power systems,power transmission with higher efficiency,and aggregation and delivery of power from offshore wind farms to different AC regions are among the main drivers for the development of HVDC grids.HVDC grids can result in lower demand variability,higher flexibility,superior electricity market management,and higher economic value.It is expected that isolated HVDC systems transition to an HVDC grid that overlays the existing AC grid.Such a substantial development also results in a number of critical technical challenges related to system control,operation,and protection,which should be properly and accurately addressed.This Special Issue focuses on the recent achievements and advancements in overcoming these challenges.Accepted papers for publications in this Special Issue fall into four major topics:devices,control,operation,and protection.展开更多
Short circuit fault occurrence in high-voltage DC (HVDC) systems causes extremely high currents in a fast raising time that does not experience current zero-crossing. To protect HVDC systems/grids against fault curren...Short circuit fault occurrence in high-voltage DC (HVDC) systems causes extremely high currents in a fast raising time that does not experience current zero-crossing. To protect HVDC systems/grids against fault current, fast HVDC breaker is an essential equipment. This study presents the design procedure of a novel HVDC breaker based on solid-state controllable reactor which is able to reduce the fault current's rate of rise and fault current amplitude to less than grid nominal current in the breaking process. The main achievement of the proposed HVDC breaker is that not only breaker does not encounter fault current, but also none of the series HVDC equipment is influenced by the fault. The designed breaker performance is studied by PSCAD/EMTPS, and then the simulation results are validated by the developed laboratory experimental setup.展开更多
文摘A few multi-terminal direct current(MTDC)systems are in operation around the world today. However,MTDC grids overlaying their AC counterpart might a reality in a near future. The main drivers for constructing such direct current grids are the large-scale integration of remote renewable energy resources into the existing alternative current(AC) grids, and the promotion and development of international energy markets through the socalled supergrids. This paper presents the most critical challenges and prospects for such emerging MTDC grids,along with a foreseeable technology development roadmap,with a particular focus on crucial control and operational issues that are associated with MTDC systems and grids.
基金supported by the West Regional Electric Company,Iran,Kermanshah.
文摘Here,using the probabilistic evaluation based on the Monte Carlo method,back-flashover rate and shielding failure flashover rate of 230 kV overhead transmission lines in the western regions of Iran are evaluated.To such an aim,first,the number of thunderstorm days per year is collected from the reported weather information in order to determine the ground flash density.Then,using MRU-200 equipment,the tower-footing resistance of several towers is measured.Matlab®software is used in order to produce lightning surges considering its probabilistic nature and randomly distribution on the ground to evaluate striking distance based on the geometric model.Then,calculated parameters are transferred to EMTP-RV software by establishing a link to perform the transient simulation and report the results for modelled 230 kV transmission line.Finally,considering IEEE-1243 standard,it is shown that due to high ground flash density,using 230 kV tower with one shield wire is not sufficient to protect the line against lightning phenomena.
文摘Interconnections between AC power systems,power transmission with higher efficiency,and aggregation and delivery of power from offshore wind farms to different AC regions are among the main drivers for the development of HVDC grids.HVDC grids can result in lower demand variability,higher flexibility,superior electricity market management,and higher economic value.It is expected that isolated HVDC systems transition to an HVDC grid that overlays the existing AC grid.Such a substantial development also results in a number of critical technical challenges related to system control,operation,and protection,which should be properly and accurately addressed.This Special Issue focuses on the recent achievements and advancements in overcoming these challenges.Accepted papers for publications in this Special Issue fall into four major topics:devices,control,operation,and protection.
文摘Short circuit fault occurrence in high-voltage DC (HVDC) systems causes extremely high currents in a fast raising time that does not experience current zero-crossing. To protect HVDC systems/grids against fault current, fast HVDC breaker is an essential equipment. This study presents the design procedure of a novel HVDC breaker based on solid-state controllable reactor which is able to reduce the fault current's rate of rise and fault current amplitude to less than grid nominal current in the breaking process. The main achievement of the proposed HVDC breaker is that not only breaker does not encounter fault current, but also none of the series HVDC equipment is influenced by the fault. The designed breaker performance is studied by PSCAD/EMTPS, and then the simulation results are validated by the developed laboratory experimental setup.
