The DC fault characteristics of voltage source converter based high voltage direct current(VSC-HVDC)systems are analyzed in this paper.The phenomenon whereby the capacitor on DC side discharges quickly during a DC fau...The DC fault characteristics of voltage source converter based high voltage direct current(VSC-HVDC)systems are analyzed in this paper.The phenomenon whereby the capacitor on DC side discharges quickly during a DC fault contributes to a large short-circuit fault current.Neither traditional DC breakers nor DC switches can cut off the fault current under this condition.A fast solid state DC breaker design method is proposed in this paper.This method is based on the fault current characteristics of the inverter in multi-terminal HVDC systems(MTDC),where a fault current appears at the natural zerocrossing point near the inverter.At this point,by coordinating the AC breakers near the rectifier,the DC breaker could reliably cut off the DC fault current and protect the system.A detailed model for this fast solid state DC breaker and its operation sequence are studied,based on this design method.Simulations modeling a five-terminal meshed DC grid and a fast DC breaker were carried out with PSCAD/EMTDC using this design method.The results from the simulations confirmed the validity of the design method.展开更多
This paper presents an integrated protection technique for power distribution systems. A novel integrated protection scheme based on overcurrent protection technique for distribution system is described, in which a sp...This paper presents an integrated protection technique for power distribution systems. A novel integrated protection scheme based on overcurrent protection technique for distribution system is described, in which a specially designed protection relay is installed at each substation of a network and responsible for the protection of every line sections connected to the substation busbar The conventional directional overcurrent and the new adaptive accelerated protection algorithms with multiple settings are implemented into the relay to cover all the protected line sections. The paper includes studies of a typical multi section distribution network to demonstrate the principle of the scheme. Studies show that the new scheme not only offer the new protection features for individual power line section, but also provide the characteristics of integrated protection.展开更多
Different methods of calibrating ultra high frequency(UHF) sensors for gas-insulated substations(GIS) were investigated in the past.The first approach was to use strip lines,triplates and TEM calibration cells.These c...Different methods of calibrating ultra high frequency(UHF) sensors for gas-insulated substations(GIS) were investigated in the past.The first approach was to use strip lines,triplates and TEM calibration cells.These cells had already been in use for years for example to test the electromagnetic compatibility of electronic devices.The smaller the size of the cell,the higher its bandwidth-but the cell should be large enough to not disturb the electric field with the installed sensor under test.To overcome this problem,a calibration procedure using a gigahertz transverse electromagnetic (GTEM) test cell and a pulsed signal source were introduced in 1997.Although this procedure has many advantages and is easy to understand,measurements show several shortcomings of this calibration method.To overcome the disadvantages of the known systems,a calibration cell using a monopole cone antenna and a metallic ground plane were developed and tested.The UHF sensor was placed in a region with minimum distortion of the electric field due to its installation.Experience shows that the new method for calibrating UHF sensors is necessary in order to overcome the limits in the calibration of large sensors and to suppress the propagation of higher order modes and reflections.Due to its surprisingly simple structure,its low price and low overall measurement uncertainty,it is the preferred method for calibrating UHF sensors for GIS applications.展开更多
The selection of an optimized restoration building block(RBB)scheme among all available schemes is one of the most important factors impacting the power system restoration process after a complete or partial blackout....The selection of an optimized restoration building block(RBB)scheme among all available schemes is one of the most important factors impacting the power system restoration process after a complete or partial blackout.This paper presents a data envelopment analysis(DEA)model used as an empirical method to assess the RBB schemes.An N-level evaluation scale cloud system is built based on cloud theory to transform qualitative I/O indices of DEA model into quantitative values.Through joint utilization of the CCR(Charnes,Cooper and Rhodes)model and the LJK(Li,Jahanshahloo and Khodabakhshi)model,the established Joint-DEA model makes the newly proposed Cloud-DEA method a more feasible and robust method in assessment of RBB schemes.展开更多
A simulation framework is proposed to evaluate the voltage stability of power systems incorporating wind power intermittency.Firstly，the power output modelings of three types of wind turbines are discussed.Secondly，...A simulation framework is proposed to evaluate the voltage stability of power systems incorporating wind power intermittency.Firstly，the power output modelings of three types of wind turbines are discussed.Secondly，the Jensen model is employed to simulate the wind farm with the wake effect.The Monte Carlo based technique is used to conduct the voltage stability evaluation incorporating the randomness of the wind speed based on the Weibull probability distribution.Thirdly，the relative sensitivity index（RSI）is calculated to identify weak buses during analysis.Finally，case studies with different simulation scenarios are carried out.Some statistical results involving weakness probability，expected value and variance of RSI as well as preliminary conclusions are drawn based on numerical simulation results.展开更多
This paper presents a case study about a condition monitoring project for asset management implementing an advanced decision process for maintenance and asset replacement in the Qatar electricity distribution network....This paper presents a case study about a condition monitoring project for asset management implementing an advanced decision process for maintenance and asset replacement in the Qatar electricity distribution network. It describes the principles used to produce an assessment of the health of the entire fleet of assets, together with the concepts retained to prioritize the interventions on the distribution network equipment. The paper goes through the actual steps taken for the preparation and execution mode of the overall project. It covers the following project phases： definition of the problem ＆ business objectives, process definition and preparation tasks, presentation of solutions and execution phase. The project being still in the implementation phase, the conclusions are preliminary but already demonstrate concrete and tangible benefits.展开更多
Co-optimizing transmission topology with generation dispatch, and leveraging grid controllability could be a viable way to improve economic efficiency of system operations in control centers. In particular, day-ahead ...Co-optimizing transmission topology with generation dispatch, and leveraging grid controllability could be a viable way to improve economic efficiency of system operations in control centers. In particular, day-ahead unit commitment is a typical business process that electric utilities deploy to ensure enough generation capacity is committed day-ahead to meet the load for the next day. In a market environment, day-ahead reliability unit commitment (DA-RUC) performs a simultaneous solution of minimizing the cost of commitment for resources to meet forecasted load, net scheduled interchange and operating reserve requirements using security constrained unit commitment (SCUC). The commitment may then be further checked by running security constrained economic dispatch (SCED) to verify that the commitment solution can be feasibly dispatched subject to system constraints and activated transmission constraints for each hour identified in the study period. This paper applies Optimal Transmission Switching (OTS) in DA-RUC using some heuristic pre-screening techniques to reduce the dimension of the OTS problem. Various pre-screening methods of candidate transmission lines for switching are proposed and compared. Simulation results will be presented to demonstrate generation dispatch combined with OTS in each hour could reduce congestion cost and significantly lower generation cost.展开更多
基金This work is supported by National Natural Science Foundation of China under the contract 51261130484by State Grid Corporation of China under the contract State Grid Research 304(2013).
文摘The DC fault characteristics of voltage source converter based high voltage direct current(VSC-HVDC)systems are analyzed in this paper.The phenomenon whereby the capacitor on DC side discharges quickly during a DC fault contributes to a large short-circuit fault current.Neither traditional DC breakers nor DC switches can cut off the fault current under this condition.A fast solid state DC breaker design method is proposed in this paper.This method is based on the fault current characteristics of the inverter in multi-terminal HVDC systems(MTDC),where a fault current appears at the natural zerocrossing point near the inverter.At this point,by coordinating the AC breakers near the rectifier,the DC breaker could reliably cut off the DC fault current and protect the system.A detailed model for this fast solid state DC breaker and its operation sequence are studied,based on this design method.Simulations modeling a five-terminal meshed DC grid and a fast DC breaker were carried out with PSCAD/EMTDC using this design method.The results from the simulations confirmed the validity of the design method.
基金Project supported by Funds for Innovative Research Groups of China （51021005）, National Basic Research Program of China （973 Program） （2009CB724504）, National Natural Science Foundation of China（50707036）.
文摘This paper presents an integrated protection technique for power distribution systems. A novel integrated protection scheme based on overcurrent protection technique for distribution system is described, in which a specially designed protection relay is installed at each substation of a network and responsible for the protection of every line sections connected to the substation busbar The conventional directional overcurrent and the new adaptive accelerated protection algorithms with multiple settings are implemented into the relay to cover all the protected line sections. The paper includes studies of a typical multi section distribution network to demonstrate the principle of the scheme. Studies show that the new scheme not only offer the new protection features for individual power line section, but also provide the characteristics of integrated protection.
文摘Different methods of calibrating ultra high frequency(UHF) sensors for gas-insulated substations(GIS) were investigated in the past.The first approach was to use strip lines,triplates and TEM calibration cells.These cells had already been in use for years for example to test the electromagnetic compatibility of electronic devices.The smaller the size of the cell,the higher its bandwidth-but the cell should be large enough to not disturb the electric field with the installed sensor under test.To overcome this problem,a calibration procedure using a gigahertz transverse electromagnetic (GTEM) test cell and a pulsed signal source were introduced in 1997.Although this procedure has many advantages and is easy to understand,measurements show several shortcomings of this calibration method.To overcome the disadvantages of the known systems,a calibration cell using a monopole cone antenna and a metallic ground plane were developed and tested.The UHF sensor was placed in a region with minimum distortion of the electric field due to its installation.Experience shows that the new method for calibrating UHF sensors is necessary in order to overcome the limits in the calibration of large sensors and to suppress the propagation of higher order modes and reflections.Due to its surprisingly simple structure,its low price and low overall measurement uncertainty,it is the preferred method for calibrating UHF sensors for GIS applications.
基金supported by the National Natural Science Foundation of China under Grant 51377103the Participation in Research Program for undergraduate students of Shanghai Jiao Tong University under Grant T030PRP26041.
文摘The selection of an optimized restoration building block(RBB)scheme among all available schemes is one of the most important factors impacting the power system restoration process after a complete or partial blackout.This paper presents a data envelopment analysis(DEA)model used as an empirical method to assess the RBB schemes.An N-level evaluation scale cloud system is built based on cloud theory to transform qualitative I/O indices of DEA model into quantitative values.Through joint utilization of the CCR(Charnes,Cooper and Rhodes)model and the LJK(Li,Jahanshahloo and Khodabakhshi)model,the established Joint-DEA model makes the newly proposed Cloud-DEA method a more feasible and robust method in assessment of RBB schemes.
基金This work is supported by National Natural Science Foundation of China （No. 50977051 ） and Research Project of Science and Technology from Shenzhen Development and Innovation Committee （No. ZDSY20120619141142918）.
文摘A simulation framework is proposed to evaluate the voltage stability of power systems incorporating wind power intermittency.Firstly，the power output modelings of three types of wind turbines are discussed.Secondly，the Jensen model is employed to simulate the wind farm with the wake effect.The Monte Carlo based technique is used to conduct the voltage stability evaluation incorporating the randomness of the wind speed based on the Weibull probability distribution.Thirdly，the relative sensitivity index（RSI）is calculated to identify weak buses during analysis.Finally，case studies with different simulation scenarios are carried out.Some statistical results involving weakness probability，expected value and variance of RSI as well as preliminary conclusions are drawn based on numerical simulation results.
文摘This paper presents a case study about a condition monitoring project for asset management implementing an advanced decision process for maintenance and asset replacement in the Qatar electricity distribution network. It describes the principles used to produce an assessment of the health of the entire fleet of assets, together with the concepts retained to prioritize the interventions on the distribution network equipment. The paper goes through the actual steps taken for the preparation and execution mode of the overall project. It covers the following project phases： definition of the problem ＆ business objectives, process definition and preparation tasks, presentation of solutions and execution phase. The project being still in the implementation phase, the conclusions are preliminary but already demonstrate concrete and tangible benefits.
文摘Co-optimizing transmission topology with generation dispatch, and leveraging grid controllability could be a viable way to improve economic efficiency of system operations in control centers. In particular, day-ahead unit commitment is a typical business process that electric utilities deploy to ensure enough generation capacity is committed day-ahead to meet the load for the next day. In a market environment, day-ahead reliability unit commitment (DA-RUC) performs a simultaneous solution of minimizing the cost of commitment for resources to meet forecasted load, net scheduled interchange and operating reserve requirements using security constrained unit commitment (SCUC). The commitment may then be further checked by running security constrained economic dispatch (SCED) to verify that the commitment solution can be feasibly dispatched subject to system constraints and activated transmission constraints for each hour identified in the study period. This paper applies Optimal Transmission Switching (OTS) in DA-RUC using some heuristic pre-screening techniques to reduce the dimension of the OTS problem. Various pre-screening methods of candidate transmission lines for switching are proposed and compared. Simulation results will be presented to demonstrate generation dispatch combined with OTS in each hour could reduce congestion cost and significantly lower generation cost.
