GaN （gallium nitride） buck-rectifier has been proposed to realize high power density ISOP （input series and output parallel）-IPOS （input parallel and output series） converter-based dc distribution system. The ul...GaN （gallium nitride） buck-rectifier has been proposed to realize high power density ISOP （input series and output parallel）-IPOS （input parallel and output series） converter-based dc distribution system. The ultra-low loss bi-directional switch can be developed by the GaN power device because of the low on-resistance, the high-speed switching behavior and its own device structure. The buck-rectifier using the GaN bi-directional switches has the potential to achieve higher power density than the commonly utilized boost-rectifier. Availability of the GaN-HEMT （high electron mobility transistor） for the buck rectifier has been verified taking the theoretical limit of the on-resistance and the switching loss energy into account. Design consideration for a high power density buck-rectifier has been also conducted and the application effect of the GaN bidirectional switches has been evaluated quantitatively. The ISOP-IPOS converter-based dc （direct current） distribution system takes full advantage of the buck-rectifier and the rectifier using GaN devices contributes to realizing higher power density dc distribution system.展开更多
The increasing flexibility of active distribution systems(ADSs)coupled with the high penetration of renewable distributed generators(RDGs)leads to the increase of the complexity.It is of practical significance to achi...The increasing flexibility of active distribution systems(ADSs)coupled with the high penetration of renewable distributed generators(RDGs)leads to the increase of the complexity.It is of practical significance to achieve the largest amount of RDG penetration in ADSs and maintain the optimal operation.This study establishes an alternating current(AC)/direct current(DC)hybrid ADS model that considers the dynamic thermal rating,soft open point,and distribution network reconfiguration(DNR).Moreover,it transforms the optimal dispatching into a second-order cone programming problem.Considering the different control time scales of dispatchable resources,the following two-stage dispatching framework is proposed.d dispatch uses hourly input data with the goal(1)The day-ahea of minimizing the grid loss and RDG dropout.It obtains the optimal 24-hour schedule to determine the dispatching plans for DNR and the energy storage system.(2)The intraday dispatch uses 15-min input data for 1-hour rolling-plan dispatch but only executes the first 15 min of dispatching.To eliminate error between the actual operation and dispatching plan,the first 15 min is divided into three 5-min step-by-step executions.The goal of each step is to trace the tie-line power of the intraday rolling-plan dispatch to the greatest extent at the minimum cost.The measured data are used as feedback input for the rolling-plan dispatch after each step is executed.A case study shows that the comprehensive cooperative ADS model can release the line capacity,reduce losses,and improve the penetration rate of RDGs.Further,the two-stage dispatching framework can handle source-load fluctuations and enhance system stability.展开更多
The high-voltage power source is one of the important research directions of triboelectric nanogenerator(TENG).In this paper,a high-voltage output TENG(HVO-TENG)is proposed with direct current/alternating current(DC/A...The high-voltage power source is one of the important research directions of triboelectric nanogenerator(TENG).In this paper,a high-voltage output TENG(HVO-TENG)is proposed with direct current/alternating current(DC/AC)optimal combination method for wind energy harvesting.Through the optimal design of a direct current generation unit(DCGU)and an alternating current generation unit(ACGU),the HVO-TENG can produce DC voltage of 21.5 kV and AC voltage of 200 V,simultaneously.The HVOTENG can continuously illuminate more than 6,000 light emitting diodes(LEDs),which is enough to drive more possible applications of TENG.Besides,this paper explored application experiments on HVO-TENG.Demonstrative experiments indicate that the high-voltage DC output is used for producing ozone,while the AC output can light up ultraviolet(UV)LEDs.The HVOTENG can increase the ozone concentration(C)in an airtight container to 3 parts per million(ppm)after 7 h and continuously light up UV LEDs.All these demonstrations verify that the HVO-TENG has important guiding significance for designing high performance TENG.展开更多
In view of the imbalanced distribution of power load and resources, including the status of “electric shortage” in some cities in our country, the article discusses the long-distance transmission technology. It main...In view of the imbalanced distribution of power load and resources, including the status of “electric shortage” in some cities in our country, the article discusses the long-distance transmission technology. It mainly analyzed two ways of the long-distance transmission: UHV AC transmission and UHV DC transmission. The fractional frequency transmission technology and half wavelength AC transmission technology of AC transmission are introduced. Some key technologies of long-distance transmission are described. It has a guess for long-distance transmission future direction.展开更多
文摘GaN （gallium nitride） buck-rectifier has been proposed to realize high power density ISOP （input series and output parallel）-IPOS （input parallel and output series） converter-based dc distribution system. The ultra-low loss bi-directional switch can be developed by the GaN power device because of the low on-resistance, the high-speed switching behavior and its own device structure. The buck-rectifier using the GaN bi-directional switches has the potential to achieve higher power density than the commonly utilized boost-rectifier. Availability of the GaN-HEMT （high electron mobility transistor） for the buck rectifier has been verified taking the theoretical limit of the on-resistance and the switching loss energy into account. Design consideration for a high power density buck-rectifier has been also conducted and the application effect of the GaN bidirectional switches has been evaluated quantitatively. The ISOP-IPOS converter-based dc （direct current） distribution system takes full advantage of the buck-rectifier and the rectifier using GaN devices contributes to realizing higher power density dc distribution system.
基金supported by Universiti Sains Malaysia through Research University Team(RUTeam)Grant Scheme(No.1001/PELECT/8580011)。
文摘The increasing flexibility of active distribution systems(ADSs)coupled with the high penetration of renewable distributed generators(RDGs)leads to the increase of the complexity.It is of practical significance to achieve the largest amount of RDG penetration in ADSs and maintain the optimal operation.This study establishes an alternating current(AC)/direct current(DC)hybrid ADS model that considers the dynamic thermal rating,soft open point,and distribution network reconfiguration(DNR).Moreover,it transforms the optimal dispatching into a second-order cone programming problem.Considering the different control time scales of dispatchable resources,the following two-stage dispatching framework is proposed.d dispatch uses hourly input data with the goal(1)The day-ahea of minimizing the grid loss and RDG dropout.It obtains the optimal 24-hour schedule to determine the dispatching plans for DNR and the energy storage system.(2)The intraday dispatch uses 15-min input data for 1-hour rolling-plan dispatch but only executes the first 15 min of dispatching.To eliminate error between the actual operation and dispatching plan,the first 15 min is divided into three 5-min step-by-step executions.The goal of each step is to trace the tie-line power of the intraday rolling-plan dispatch to the greatest extent at the minimum cost.The measured data are used as feedback input for the rolling-plan dispatch after each step is executed.A case study shows that the comprehensive cooperative ADS model can release the line capacity,reduce losses,and improve the penetration rate of RDGs.Further,the two-stage dispatching framework can handle source-load fluctuations and enhance system stability.
基金National Key R&D Project from the Minister of Science and Technology(Nos.2016YFA0202701 and 2016YFA0202704)the Beijing Municipal Science and Technology Commission(No.Z171100002017017).
文摘The high-voltage power source is one of the important research directions of triboelectric nanogenerator(TENG).In this paper,a high-voltage output TENG(HVO-TENG)is proposed with direct current/alternating current(DC/AC)optimal combination method for wind energy harvesting.Through the optimal design of a direct current generation unit(DCGU)and an alternating current generation unit(ACGU),the HVO-TENG can produce DC voltage of 21.5 kV and AC voltage of 200 V,simultaneously.The HVOTENG can continuously illuminate more than 6,000 light emitting diodes(LEDs),which is enough to drive more possible applications of TENG.Besides,this paper explored application experiments on HVO-TENG.Demonstrative experiments indicate that the high-voltage DC output is used for producing ozone,while the AC output can light up ultraviolet(UV)LEDs.The HVOTENG can increase the ozone concentration(C)in an airtight container to 3 parts per million(ppm)after 7 h and continuously light up UV LEDs.All these demonstrations verify that the HVO-TENG has important guiding significance for designing high performance TENG.
文摘In view of the imbalanced distribution of power load and resources, including the status of “electric shortage” in some cities in our country, the article discusses the long-distance transmission technology. It mainly analyzed two ways of the long-distance transmission: UHV AC transmission and UHV DC transmission. The fractional frequency transmission technology and half wavelength AC transmission technology of AC transmission are introduced. Some key technologies of long-distance transmission are described. It has a guess for long-distance transmission future direction.
