In this paper,a VSG(virtual synchronous generator)-based method with adaptive active power and DC voltage droop is proposed for the control of VSC stations in the multi-terminal DC(MTDC)system.This control strategy ca...In this paper,a VSG(virtual synchronous generator)-based method with adaptive active power and DC voltage droop is proposed for the control of VSC stations in the multi-terminal DC(MTDC)system.This control strategy can improve the inertial level of the AC networks and attenuate the rate of change of frequency when a disturbance occurs.In addition,the droop control of the active power and DC voltage is implemented to make the AC networks share the unbalanced power in the MTDC.The droop coefficients are adaptively adjusted depending on the frequency margin of every AC network,which makes the allocation of unbalanced power among AC networks more reasonable from the frequency variation perspective.The control strategy is evaluated in the scenarios of sudden load change and wind turbine tripping,and the results are presented to demonstrate its effectiveness.展开更多
As an effective approach of implementing power load shifting,fostering the accommodation of renewable energy,such as the wind and solar generation,energy storage technique is playing an important role in the smart gri...As an effective approach of implementing power load shifting,fostering the accommodation of renewable energy,such as the wind and solar generation,energy storage technique is playing an important role in the smart grid and energy internet.Compressed air energy storage(CAES) is a promising energy storage technology due to its cleanness,high efficiency,low cost,and long service life.This paper surveys state-of-the-art technologies of CAES,and makes endeavors to demonstrate the fundamental principles,classifications and operation modes of CAES.Critical subsystems of CAES are elaborated exhaustively.The application prospects and further research directions are summarized to promote the popularization of CAES in smart grid and energy internet.展开更多
Beef and mutton production has been aided by breeding to integrate allelic diversity for myostatin(MSTN),but a lack of diversity in the MSTN germplasm has limited similar advances in pig farming.Moreover,insurmountabl...Beef and mutton production has been aided by breeding to integrate allelic diversity for myostatin(MSTN),but a lack of diversity in the MSTN germplasm has limited similar advances in pig farming.Moreover,insurmountable challenges with congenital lameness and a dearth of data about the impacts of feed conversion,reproduction,and meat quality in MSTN-edited pigs have also currently blocked progress.Here,in a largest-to-date evaluation of multiple MSTN-edited pig populations,we demonstrated a practical alternative edit-site-based solution that overcomes the major production obstacle of hindlimb weakness.We also provide long-term and multidomain datasets for multiple breeds that illustrate how MSTN-editing can sustainably increase the yields of breed-specific lean meat and the levels of desirable lipids without deleteriously affecting feed-conversion rates or litter size.Apart from establishing a new benchmark for the data scale and quality of genome-edited animal production,our study specifically illustrates how gene-editing site selection profoundly impacts the phenotypic outcomes in diverse genetic back-grounds.展开更多
Virtual synchronous generator(VSG)is gridfriendly for integrating distributed generations(DGs)since it can emulate the operation mechanism of traditional synchronous generator(SG).However,the traditional VSG control s...Virtual synchronous generator(VSG)is gridfriendly for integrating distributed generations(DGs)since it can emulate the operation mechanism of traditional synchronous generator(SG).However,the traditional VSG control strategy,which is mainly suitable for balanced voltage conditions,may lead to power oscillations,current unbalance and even overcurrent under unbalanced voltage sags.To overcome this difficulty,a flexible unbalanced control with peak current limitation for VSG under unbalanced operating conditions is proposed.Based on the basic VSG control algorithm,the control strategy integrates two novel control modules,which are current reference generator(CRG)and power reference generator(PRG).The proposed control strategy can flexibly meet different operation demands,which includes current balancing,constant active or reactive power.And the injected currents are kept within safety values for a better utilization of the VSG power capacity.Furthermore,the experimental platform is built.Experimental results demonstrate the validness and effectiveness of the proposed control strategy.展开更多
Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annulus with narrow gap is bilaterally heated by AC ...Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annulus with narrow gap is bilaterally heated by AC current power supply. The experimental conditions covered a range of pressure from 0.8 to 3.5 MPa, mass flux of 26.6 to 68.8 kg?m-2?s-1 and wall heat flux of 5 to 50 kW?m-2. The location of dryout is obtained by observing a sudden rise in surface temperature. Kutateladze correlation is cited and modified to predict the location of dryout and proved to be not a proper one. Considering in detail the effects of geometry of annuli, pressure, mass flux and heat flux on dryout, an empirical correction is finally developed to predict dryout point in narrow annular gap under low flow condition, which has a good agreement with experimental data.展开更多
A consensus-based distributed control method of coordinated VSGs with communication time delays in isolate microgrid is proposed. When time delays are considered in communication, there are some effects on frequency r...A consensus-based distributed control method of coordinated VSGs with communication time delays in isolate microgrid is proposed. When time delays are considered in communication, there are some effects on frequency restoration and active power output allocation. In the control structure, only local information exchange is needed, while the final frequency can be controlled to the nominal value and the VSGs can automatically share loads according to their rated values. An AC microgrid with three VSGs and some loads is implemented. The proposed control strategy is verified by MATLAB/ Simulink simulation results.展开更多
L-malate is an intermediate of the tricarboxylic acid cycle which is naturally occurred in various microorganisms,and it has been widely applied in polymer,beverage and food,textile,agricultural and pharmaceutical ind...L-malate is an intermediate of the tricarboxylic acid cycle which is naturally occurred in various microorganisms,and it has been widely applied in polymer,beverage and food,textile,agricultural and pharmaceutical industries.Driven by the pursuit of a sustainable economy,microbial production of L-malate has received much attention in last decades.In this review,we focus on the utilization of wastes and/or byproducts as feedstocks for the microbial production of L-malate.Firstly,we present the recent developments on the natural or engineered metabolic pathways that dedicate to the biosynthesis of L-malate,and also provide a comprehensive discussions on developing high-efficient producers.Then,the recent achievements in microbial production of L-malate from various carbon sources were concluded and discussed.Furthermore,some abundant non-food feedstocks which have been used for microbial production of other chemicals were reviewed,as they may be potential candidate feedstock for L-malate production in future.Finally,we outlined the major challenges and proposed further improvements for the production of L-malate.展开更多
基金supported by the National Nature Science Foundation of China(51621065,51567021)Independent Research Program of Tsinghua University(20151080416)China Postdoctoral Science Foundation(2016M601025).
文摘In this paper,a VSG(virtual synchronous generator)-based method with adaptive active power and DC voltage droop is proposed for the control of VSC stations in the multi-terminal DC(MTDC)system.This control strategy can improve the inertial level of the AC networks and attenuate the rate of change of frequency when a disturbance occurs.In addition,the droop control of the active power and DC voltage is implemented to make the AC networks share the unbalanced power in the MTDC.The droop coefficients are adaptively adjusted depending on the frequency margin of every AC network,which makes the allocation of unbalanced power among AC networks more reasonable from the frequency variation perspective.The control strategy is evaluated in the scenarios of sudden load change and wind turbine tripping,and the results are presented to demonstrate its effectiveness.
基金supported by National Natural Science Foundation of China(No.51321005)
文摘As an effective approach of implementing power load shifting,fostering the accommodation of renewable energy,such as the wind and solar generation,energy storage technique is playing an important role in the smart grid and energy internet.Compressed air energy storage(CAES) is a promising energy storage technology due to its cleanness,high efficiency,low cost,and long service life.This paper surveys state-of-the-art technologies of CAES,and makes endeavors to demonstrate the fundamental principles,classifications and operation modes of CAES.Critical subsystems of CAES are elaborated exhaustively.The application prospects and further research directions are summarized to promote the popularization of CAES in smart grid and energy internet.
基金the National Major Transgenic Breeding Project(2008ZX08006-003,2011ZX08006-003,2013ZX08006-003,2014ZX08006-003,and 2016ZX08006-001)the Na-tional Key Basic Research Development Plan(2015CB943100)+1 种基金the Key Projects of the National Natural Science Foundation of China(30830080 and 31330074)China Postdoctoral Foundation Project(2018M631648)。
文摘Beef and mutton production has been aided by breeding to integrate allelic diversity for myostatin(MSTN),but a lack of diversity in the MSTN germplasm has limited similar advances in pig farming.Moreover,insurmountable challenges with congenital lameness and a dearth of data about the impacts of feed conversion,reproduction,and meat quality in MSTN-edited pigs have also currently blocked progress.Here,in a largest-to-date evaluation of multiple MSTN-edited pig populations,we demonstrated a practical alternative edit-site-based solution that overcomes the major production obstacle of hindlimb weakness.We also provide long-term and multidomain datasets for multiple breeds that illustrate how MSTN-editing can sustainably increase the yields of breed-specific lean meat and the levels of desirable lipids without deleteriously affecting feed-conversion rates or litter size.Apart from establishing a new benchmark for the data scale and quality of genome-edited animal production,our study specifically illustrates how gene-editing site selection profoundly impacts the phenotypic outcomes in diverse genetic back-grounds.
基金supported by National Natural Science Foundation of China (No.51321005)Independent Research Program of Tsinghua University (No.20151080416)Area Foundation of National Natural Science Foundation of China (No.51567021)
文摘Virtual synchronous generator(VSG)is gridfriendly for integrating distributed generations(DGs)since it can emulate the operation mechanism of traditional synchronous generator(SG).However,the traditional VSG control strategy,which is mainly suitable for balanced voltage conditions,may lead to power oscillations,current unbalance and even overcurrent under unbalanced voltage sags.To overcome this difficulty,a flexible unbalanced control with peak current limitation for VSG under unbalanced operating conditions is proposed.Based on the basic VSG control algorithm,the control strategy integrates two novel control modules,which are current reference generator(CRG)and power reference generator(PRG).The proposed control strategy can flexibly meet different operation demands,which includes current balancing,constant active or reactive power.And the injected currents are kept within safety values for a better utilization of the VSG power capacity.Furthermore,the experimental platform is built.Experimental results demonstrate the validness and effectiveness of the proposed control strategy.
文摘Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annulus with narrow gap is bilaterally heated by AC current power supply. The experimental conditions covered a range of pressure from 0.8 to 3.5 MPa, mass flux of 26.6 to 68.8 kg?m-2?s-1 and wall heat flux of 5 to 50 kW?m-2. The location of dryout is obtained by observing a sudden rise in surface temperature. Kutateladze correlation is cited and modified to predict the location of dryout and proved to be not a proper one. Considering in detail the effects of geometry of annuli, pressure, mass flux and heat flux on dryout, an empirical correction is finally developed to predict dryout point in narrow annular gap under low flow condition, which has a good agreement with experimental data.
文摘A consensus-based distributed control method of coordinated VSGs with communication time delays in isolate microgrid is proposed. When time delays are considered in communication, there are some effects on frequency restoration and active power output allocation. In the control structure, only local information exchange is needed, while the final frequency can be controlled to the nominal value and the VSGs can automatically share loads according to their rated values. An AC microgrid with three VSGs and some loads is implemented. The proposed control strategy is verified by MATLAB/ Simulink simulation results.
基金This work was supported by the National Key R&D Program of China(2018YFA0901500)the National Natural Science Foundation of China(21706124,21727818)+1 种基金the Key Science and Technology Project of Jiangsu Province(BE2016389)the Jiangsu Synergetic Innovation Center for Advanced Bio-Manufacture of China.
文摘L-malate is an intermediate of the tricarboxylic acid cycle which is naturally occurred in various microorganisms,and it has been widely applied in polymer,beverage and food,textile,agricultural and pharmaceutical industries.Driven by the pursuit of a sustainable economy,microbial production of L-malate has received much attention in last decades.In this review,we focus on the utilization of wastes and/or byproducts as feedstocks for the microbial production of L-malate.Firstly,we present the recent developments on the natural or engineered metabolic pathways that dedicate to the biosynthesis of L-malate,and also provide a comprehensive discussions on developing high-efficient producers.Then,the recent achievements in microbial production of L-malate from various carbon sources were concluded and discussed.Furthermore,some abundant non-food feedstocks which have been used for microbial production of other chemicals were reviewed,as they may be potential candidate feedstock for L-malate production in future.Finally,we outlined the major challenges and proposed further improvements for the production of L-malate.
