A parameter that allows an evaluation of power quality transmitted, or distributed, between energy source and the final user is electric system power factor. Among other aspects, a bigger power factor, close to unit v...A parameter that allows an evaluation of power quality transmitted, or distributed, between energy source and the final user is electric system power factor. Among other aspects, a bigger power factor, close to unit value, relieves operational conditions of lines and cables, besides, it improves feeder＇s voltage behavior. Due to load variation along the day, the dynamic compensation of power factor allows maintaining this parameter close to the ideal. This paper brings a study about a reactive dynamic compensator based on the voltage control in a capacitive element, varying the reactive energy in accordance with the system demand, everything from the energy efficiency point of view. In distribution systems, the losses due to this variable compensation can be lower than in other compensation methods and also the voltage presents a better behavior, justifying its application.展开更多
In a smart grid, electric loads are supplied by various DC （direct current） power sources, such as solar cells or batteries. On the other hand, traditional AC （alternating current） loads like a directly connected ...In a smart grid, electric loads are supplied by various DC （direct current） power sources, such as solar cells or batteries. On the other hand, traditional AC （alternating current） loads like a directly connected induction motors will also be used. In the circumstances, a smart power conversion unit is one of key components, which can integrate these DC or AC apparatus and trade power among them. Authors have developed an integrated power converter based on a well-known circuit topology of flying capacitor multilevel converter. This paper describes the detail of the circuit topology and its characteristics depending on designed parameters. The achieved power quality is also verified by simulation study.展开更多
Distribution networks face an increasing penetration of solar PV （photovoltaic） and small WTG （wind turbine generator） as well as other forms of micro-generation. To this scenario, one must add the dissemination o...Distribution networks face an increasing penetration of solar PV （photovoltaic） and small WTG （wind turbine generator） as well as other forms of micro-generation. To this scenario, one must add the dissemination of non-linear loads such as EV （electric vehicles）. There is something in common between those loads and sources： the extensive use of power electronic converters with commutated switches. These devices may be a source of medium-to-high frequency harmonic distortion and their impact on the local distribution grid must be carefully assessed in order to evaluate their negative impacts on the network, on the existing conventional loads and also on other active devices. In this paper, methodologies to characterize effects such as： harmonics, network unbalances, damaging power line resonance conditions, and over/under voltages are described and applied to a real local grid configuration.展开更多
With large-scale use of kinds of motors, oilfield drilling electrical system always accompanied by serious power quality problem, including reactive current, harmonics current and grid voltage distortion, which would ...With large-scale use of kinds of motors, oilfield drilling electrical system always accompanied by serious power quality problem, including reactive current, harmonics current and grid voltage distortion, which would greatly threaten the safety and proper working of the whole system. This paper focuses on a power quality improvement project to solve these problems. A hybrid compensating scheme, including an active compensator and a passive compensator, is carried out. Because of the specificity of oilfield drilling electrical system, compensators are redesigned against features of this application background. And then the current detection point arrangement of this hybrid system is also taken into consideration to build the whole system much more effective and reliable. Now the improvement project is already implemented in application field, and the power quality of the system is greatly improved.展开更多
Distribution systems operators are often confronted with declined power quality, which can cause substantial economical losses. The problem analyzed in paper concerns thyristor controlled direct current motor used for...Distribution systems operators are often confronted with declined power quality, which can cause substantial economical losses. The problem analyzed in paper concerns thyristor controlled direct current motor used for ski-lift in ski resort as a source of disturbances with negative impact on sensitive electric equipment, which is then unable to operate correctly. To solve mentioned problems, series of measurements of voltage quality parameters were carried out according to the respective valid standards. Crucial power quality parameters necessary for parallel power active filter design were then analyzed. Power active filter compensates power factor and filters characteristic current harmonics. After power active filter was put into operation, power quality problems were eliminated. Payback period is estimated up to four years.展开更多
A hydrophilic radical polymer, poly（2,2,6,6-teteramethylpiperidinyloxyl-4-yl acrylamide） （PTAm）, was synthesized via oxidation of the corresponding precursor polymer, poly（2,2,6,6-teteramethylpiperidine-4-yl acry...A hydrophilic radical polymer, poly（2,2,6,6-teteramethylpiperidinyloxyl-4-yl acrylamide） （PTAm）, was synthesized via oxidation of the corresponding precursor polymer, poly（2,2,6,6-teteramethylpiperidine-4-yl acrylamide）. Electrochemical properties of the PTAm layer were characterized in three aqueous electrolytes of sodium chloride （NaCl）, sodium tetrafluoroborate （NaBF4）, and sodium hexafluorophosphate （NaPF6） to optimize its activity as an organic cathode. The counter anion species significantly affected the capacity and the cycle performance of the PTAm layer. The PTAm layer in the presence of BF4？ displayed quantitative redox capacity beyond 1 μm layer thickness and maintained the discharging capacity of 110 mAh g-1 （97% vs. the calculated capacity） even after 1000 cycle charging/discharging, which could be ascribed to its appropriate affinity to the aqueous electrolyte without any dissolution into the electrolyte. A totally organic-based rechargeable cell was fabricated using PTAm and poly（N-4,4＇-bipyridinium-N-decamethylene dibromide） as the cathode and the anode, respectively, and the aqueous electrolyte of NaBF4. The cell gave a plateau voltage at 1.2 V both on charging and discharging and an excellent charging/discharging cyclability of ＆gt;2000 with high coulombic efficiency of ＆gt;95%.展开更多
文摘A parameter that allows an evaluation of power quality transmitted, or distributed, between energy source and the final user is electric system power factor. Among other aspects, a bigger power factor, close to unit value, relieves operational conditions of lines and cables, besides, it improves feeder＇s voltage behavior. Due to load variation along the day, the dynamic compensation of power factor allows maintaining this parameter close to the ideal. This paper brings a study about a reactive dynamic compensator based on the voltage control in a capacitive element, varying the reactive energy in accordance with the system demand, everything from the energy efficiency point of view. In distribution systems, the losses due to this variable compensation can be lower than in other compensation methods and also the voltage presents a better behavior, justifying its application.
文摘In a smart grid, electric loads are supplied by various DC （direct current） power sources, such as solar cells or batteries. On the other hand, traditional AC （alternating current） loads like a directly connected induction motors will also be used. In the circumstances, a smart power conversion unit is one of key components, which can integrate these DC or AC apparatus and trade power among them. Authors have developed an integrated power converter based on a well-known circuit topology of flying capacitor multilevel converter. This paper describes the detail of the circuit topology and its characteristics depending on designed parameters. The achieved power quality is also verified by simulation study.
文摘Distribution networks face an increasing penetration of solar PV （photovoltaic） and small WTG （wind turbine generator） as well as other forms of micro-generation. To this scenario, one must add the dissemination of non-linear loads such as EV （electric vehicles）. There is something in common between those loads and sources： the extensive use of power electronic converters with commutated switches. These devices may be a source of medium-to-high frequency harmonic distortion and their impact on the local distribution grid must be carefully assessed in order to evaluate their negative impacts on the network, on the existing conventional loads and also on other active devices. In this paper, methodologies to characterize effects such as： harmonics, network unbalances, damaging power line resonance conditions, and over/under voltages are described and applied to a real local grid configuration.
文摘With large-scale use of kinds of motors, oilfield drilling electrical system always accompanied by serious power quality problem, including reactive current, harmonics current and grid voltage distortion, which would greatly threaten the safety and proper working of the whole system. This paper focuses on a power quality improvement project to solve these problems. A hybrid compensating scheme, including an active compensator and a passive compensator, is carried out. Because of the specificity of oilfield drilling electrical system, compensators are redesigned against features of this application background. And then the current detection point arrangement of this hybrid system is also taken into consideration to build the whole system much more effective and reliable. Now the improvement project is already implemented in application field, and the power quality of the system is greatly improved.
文摘Distribution systems operators are often confronted with declined power quality, which can cause substantial economical losses. The problem analyzed in paper concerns thyristor controlled direct current motor used for ski-lift in ski resort as a source of disturbances with negative impact on sensitive electric equipment, which is then unable to operate correctly. To solve mentioned problems, series of measurements of voltage quality parameters were carried out according to the respective valid standards. Crucial power quality parameters necessary for parallel power active filter design were then analyzed. Power active filter compensates power factor and filters characteristic current harmonics. After power active filter was put into operation, power quality problems were eliminated. Payback period is estimated up to four years.
基金supported by Grants-in-Aid for Scientific Research (19105003)Global COE Program at Waseda University from MEXT, JapanResearch Project "Radical Polymers" at Advanced Research Institute for Science & Engineering, Waseda University
文摘A hydrophilic radical polymer, poly（2,2,6,6-teteramethylpiperidinyloxyl-4-yl acrylamide） （PTAm）, was synthesized via oxidation of the corresponding precursor polymer, poly（2,2,6,6-teteramethylpiperidine-4-yl acrylamide）. Electrochemical properties of the PTAm layer were characterized in three aqueous electrolytes of sodium chloride （NaCl）, sodium tetrafluoroborate （NaBF4）, and sodium hexafluorophosphate （NaPF6） to optimize its activity as an organic cathode. The counter anion species significantly affected the capacity and the cycle performance of the PTAm layer. The PTAm layer in the presence of BF4？ displayed quantitative redox capacity beyond 1 μm layer thickness and maintained the discharging capacity of 110 mAh g-1 （97% vs. the calculated capacity） even after 1000 cycle charging/discharging, which could be ascribed to its appropriate affinity to the aqueous electrolyte without any dissolution into the electrolyte. A totally organic-based rechargeable cell was fabricated using PTAm and poly（N-4,4＇-bipyridinium-N-decamethylene dibromide） as the cathode and the anode, respectively, and the aqueous electrolyte of NaBF4. The cell gave a plateau voltage at 1.2 V both on charging and discharging and an excellent charging/discharging cyclability of ＆gt;2000 with high coulombic efficiency of ＆gt;95%.
