基于脉冲密度调制PDM(pulse density modulation)的双边协同控制使得无线电能传输WPT(wireless power transfer)系统在耦合系数和负载阻抗变化的情况下能够保持最大效率传输,但是在系统启动及电池恒流恒压充电切换时会产生远高于额定值...基于脉冲密度调制PDM(pulse density modulation)的双边协同控制使得无线电能传输WPT(wireless power transfer)系统在耦合系数和负载阻抗变化的情况下能够保持最大效率传输,但是在系统启动及电池恒流恒压充电切换时会产生远高于额定值的电流/电压超调。为了解决超调问题,保证电池充电稳定性,提出了一种抗饱和控制策略。首先,基于WPT系统的等效电路模型分析最大效率点跟踪的工作原理;然后,结合WPT系统两侧控制量的协同工作过程,解析系统启动及电池恒流恒压充电切换时的超调现象,给出恒流恒压控制器设计方法,将反计算抗饱和算法与控制器设计相结合,提出抗饱和控制策略;最后,搭建了仿真模型,验证所提出的抗饱和策略能够有效抑制控制器饱和导致的超调,减少系统到达稳态的时间,降低电流/电压的超调带来的元器件应力。展开更多
Maximum power output of a class of irreversible non-regeneration heat engines with non-uniform working fluid,in which heat transfers between the working fluid and the heat reservoirs obey the linear phenomenological h...Maximum power output of a class of irreversible non-regeneration heat engines with non-uniform working fluid,in which heat transfers between the working fluid and the heat reservoirs obey the linear phenomenological heat transfer law [q ∝Δ(T-1)],are studied in this paper. Optimal control theory is used to determine the upper bounds of power of the heat engine for the lumped-parameter model and the distributed-parameter model,respectively. The results show that the maximum power output of the heat engine in the distributed-parameter model is less than or equal to that in the lumped-parameter model,which could provide more realistic guidelines for real heat engines. Analytical solutions of the maximum power output are obtained for the irreversible heat engines working between constant temperature reservoirs. For the irreversible heat engine operating between variable temperature reservoirs,a numerical example for the lumped-parameter model is provided by numerical calculation. The effects of changes of reservoir's temperature on the maximum power of the heat engine are analyzed. The obtained results are,in addition,compared with those obtained with Newtonian heat transfer law [q ∝Δ(T)].展开更多
Compared with endoreversible heat engine with pure heat transfer and endoreversible isothermal chemical engine with pure mass transfer,endoreversible non-isothermal chemical engine(ENICE)is a more reasonable model of ...Compared with endoreversible heat engine with pure heat transfer and endoreversible isothermal chemical engine with pure mass transfer,endoreversible non-isothermal chemical engine(ENICE)is a more reasonable model of practical mass exchanger,solid device and chemo-electric systems.There exists heat and mass transfer(HMT)simultaneously between working fluid and chemical potential reservoir in ENICE.There is coupled HMT effect that in ENICE should be considered.There are two ways to consider this coupled effect.One is based on Onsager equations,and another is based on Lewis analogy.For the mathematical and physical description of the above HMT process,the model using Onsager equations are more appropriate in the linear HMT region not far from the equilibrium state,while that based on Lewis analogy is more appropriate in nonlinear HMT region far from the equilibrium state.Different from the previous research on the power optimization of ENICEs with Onsager equations,this paper optimizes power and efficiency of ENICE based on Lewis analogy.HMT processes are assumed to obey Newtonian heat transfer law(q∝ΔT,and T is temperature)and Fick's diffusive mass transfer law(g∝Δc,and c is concentration),respectively.Analytical results of power output and corresponding vector efficiency(η_(T)andη_(μ))of ENICE are obtained,which provide important parallel results with those based on Onsager equations.They include special cases for endoreversible Carnot heat engine with q∝ΔT and endoreversible isothermal chemical engine with g∝Δc.Adopting Lewis analogy in the modelling of ENICEs with simultaneous HMT is an important work.It provides important analytical and numerical results different from those with Onsager equations obtained previously and enriches the research contents of FTT.The research results in this paper have a certain guiding significance for the optimal designs of single irreversible NICEs,multistage NICE systems,practical mass exchangers,solid devices,chemo-electric systems,and so on.展开更多
A multistage endoreversible Carnot heat engine system operating between a finite thermal capacity high-temperature fluid reservoir and an infinite thermal capacity low-temperature environment with generalized convecti...A multistage endoreversible Carnot heat engine system operating between a finite thermal capacity high-temperature fluid reservoir and an infinite thermal capacity low-temperature environment with generalized convective heat transfer law [q∝(ΔT) m ] is investigated in this paper.Optimal control theory is applied to derive the continuous Hamilton-Jacobi-Bellman (HJB) equations,which determine the optimal fluid temperature configurations for maximum power output under the conditions of fixed initial time and fixed initial temperature of the driving fluid.Based on the universal optimization results,the analytical solution for the Newtonian heat transfer law (m=1) is also obtained.Since there are no analytical solutions for the other heat transfer laws (m≠1),the continuous HJB equations are discretized and dynamic programming algorithm is performed to obtain the complete numerical solutions of the optimization problem.The relationships among the maximum power output of the system,the process period and the fluid temperature are discussed in detail.The results obtained provide some theoretical guidelines for the optimal design and operation of practical energy conversion systems.展开更多
Microbial fuel cells(MFCs)employing Pseudomonas putida B6-2(ATCC BAA-2545)as an exoelectrogen have been developed to harness energy from various conventional substrates,such as acetate,lactate,glucose,and fructose.Owi...Microbial fuel cells(MFCs)employing Pseudomonas putida B6-2(ATCC BAA-2545)as an exoelectrogen have been developed to harness energy from various conventional substrates,such as acetate,lactate,glucose,and fructose.Owing to its metabolic versatility,P.putida B6-2 demonstrates adaptable growth rates on diverse,cost-effective carbon sources within MFCs,exhibiting distinct energy production characteristics.Notably,the anode chamber’s pH rises with carboxylates’(acetate and lactate)consumption and decreases with carbohydrates’(glucose and fructose)utilization.The MFC utilizing fructose as a substrate achieved the highest power density at 411 mW m^(−2).Initial analysis revealed that P.putida B6-2 forms biofilms covered with nanowires,contributing to bioelectricity generation.These microbial nanowires are likely key players in direct extracellular electron transport through physical contact.This study established a robust foundation for producing valuable compounds and bioenergy from common substrates in bioelectrochemical systems(BESs)utilizing P.putida as an exoelectrogen.展开更多
为了研究长距离交流输电线路上并联电抗器布置对功率传输的影响,基于长距离超、特高压输电线路分布参数等效电路及二端口模型,分析了传输线路的最大传输功率及最大传输效率,推导了串补条件下两种并联电抗器布置方案的级联传输矩阵。采用...为了研究长距离交流输电线路上并联电抗器布置对功率传输的影响,基于长距离超、特高压输电线路分布参数等效电路及二端口模型,分析了传输线路的最大传输功率及最大传输效率,推导了串补条件下两种并联电抗器布置方案的级联传输矩阵。采用500 k V、1 100 k V线路典型参数,针对并联电抗器布置对最大传输功率与最大传输效率的影响进行数值模拟分析。研究结果表明并联电抗器位置在发送端与中点串补电容之间或者接收端与中点串补电容之间变化时,最大传输功率与最大传输效率均随其位置变化而发生变化。同时,并联电抗器补偿度也会影响功率传输,随着并联电抗器补偿度的增加最大传输功率及最大传输效率均会降低。展开更多
文摘基于脉冲密度调制PDM(pulse density modulation)的双边协同控制使得无线电能传输WPT(wireless power transfer)系统在耦合系数和负载阻抗变化的情况下能够保持最大效率传输,但是在系统启动及电池恒流恒压充电切换时会产生远高于额定值的电流/电压超调。为了解决超调问题,保证电池充电稳定性,提出了一种抗饱和控制策略。首先,基于WPT系统的等效电路模型分析最大效率点跟踪的工作原理;然后,结合WPT系统两侧控制量的协同工作过程,解析系统启动及电池恒流恒压充电切换时的超调现象,给出恒流恒压控制器设计方法,将反计算抗饱和算法与控制器设计相结合,提出抗饱和控制策略;最后,搭建了仿真模型,验证所提出的抗饱和策略能够有效抑制控制器饱和导致的超调,减少系统到达稳态的时间,降低电流/电压的超调带来的元器件应力。
基金Supported by the Program for New Century Excellent Talents in University of China (Grant No. 20041006)the Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No. 200136)
文摘Maximum power output of a class of irreversible non-regeneration heat engines with non-uniform working fluid,in which heat transfers between the working fluid and the heat reservoirs obey the linear phenomenological heat transfer law [q ∝Δ(T-1)],are studied in this paper. Optimal control theory is used to determine the upper bounds of power of the heat engine for the lumped-parameter model and the distributed-parameter model,respectively. The results show that the maximum power output of the heat engine in the distributed-parameter model is less than or equal to that in the lumped-parameter model,which could provide more realistic guidelines for real heat engines. Analytical solutions of the maximum power output are obtained for the irreversible heat engines working between constant temperature reservoirs. For the irreversible heat engine operating between variable temperature reservoirs,a numerical example for the lumped-parameter model is provided by numerical calculation. The effects of changes of reservoir's temperature on the maximum power of the heat engine are analyzed. The obtained results are,in addition,compared with those obtained with Newtonian heat transfer law [q ∝Δ(T)].
基金supported by the National Natural Science Foundation of China(Grant Nos.51976235 and 52171317)。
文摘Compared with endoreversible heat engine with pure heat transfer and endoreversible isothermal chemical engine with pure mass transfer,endoreversible non-isothermal chemical engine(ENICE)is a more reasonable model of practical mass exchanger,solid device and chemo-electric systems.There exists heat and mass transfer(HMT)simultaneously between working fluid and chemical potential reservoir in ENICE.There is coupled HMT effect that in ENICE should be considered.There are two ways to consider this coupled effect.One is based on Onsager equations,and another is based on Lewis analogy.For the mathematical and physical description of the above HMT process,the model using Onsager equations are more appropriate in the linear HMT region not far from the equilibrium state,while that based on Lewis analogy is more appropriate in nonlinear HMT region far from the equilibrium state.Different from the previous research on the power optimization of ENICEs with Onsager equations,this paper optimizes power and efficiency of ENICE based on Lewis analogy.HMT processes are assumed to obey Newtonian heat transfer law(q∝ΔT,and T is temperature)and Fick's diffusive mass transfer law(g∝Δc,and c is concentration),respectively.Analytical results of power output and corresponding vector efficiency(η_(T)andη_(μ))of ENICE are obtained,which provide important parallel results with those based on Onsager equations.They include special cases for endoreversible Carnot heat engine with q∝ΔT and endoreversible isothermal chemical engine with g∝Δc.Adopting Lewis analogy in the modelling of ENICEs with simultaneous HMT is an important work.It provides important analytical and numerical results different from those with Onsager equations obtained previously and enriches the research contents of FTT.The research results in this paper have a certain guiding significance for the optimal designs of single irreversible NICEs,multistage NICE systems,practical mass exchangers,solid devices,chemo-electric systems,and so on.
基金supported by the National Natural Science Foundation of China(10905093)the Program for New Century Excellent Talents in University of China(NCET-04-1006)the Foundation for the Author of National Excellent Doctoral Dissertation of China(200136)
文摘A multistage endoreversible Carnot heat engine system operating between a finite thermal capacity high-temperature fluid reservoir and an infinite thermal capacity low-temperature environment with generalized convective heat transfer law [q∝(ΔT) m ] is investigated in this paper.Optimal control theory is applied to derive the continuous Hamilton-Jacobi-Bellman (HJB) equations,which determine the optimal fluid temperature configurations for maximum power output under the conditions of fixed initial time and fixed initial temperature of the driving fluid.Based on the universal optimization results,the analytical solution for the Newtonian heat transfer law (m=1) is also obtained.Since there are no analytical solutions for the other heat transfer laws (m≠1),the continuous HJB equations are discretized and dynamic programming algorithm is performed to obtain the complete numerical solutions of the optimization problem.The relationships among the maximum power output of the system,the process period and the fluid temperature are discussed in detail.The results obtained provide some theoretical guidelines for the optimal design and operation of practical energy conversion systems.
基金supported by grants from National Natural Science Foundation of China (32070097 and 91951202)National Key Research and Development Program of China (2019YFA0904800).
文摘Microbial fuel cells(MFCs)employing Pseudomonas putida B6-2(ATCC BAA-2545)as an exoelectrogen have been developed to harness energy from various conventional substrates,such as acetate,lactate,glucose,and fructose.Owing to its metabolic versatility,P.putida B6-2 demonstrates adaptable growth rates on diverse,cost-effective carbon sources within MFCs,exhibiting distinct energy production characteristics.Notably,the anode chamber’s pH rises with carboxylates’(acetate and lactate)consumption and decreases with carbohydrates’(glucose and fructose)utilization.The MFC utilizing fructose as a substrate achieved the highest power density at 411 mW m^(−2).Initial analysis revealed that P.putida B6-2 forms biofilms covered with nanowires,contributing to bioelectricity generation.These microbial nanowires are likely key players in direct extracellular electron transport through physical contact.This study established a robust foundation for producing valuable compounds and bioenergy from common substrates in bioelectrochemical systems(BESs)utilizing P.putida as an exoelectrogen.
文摘为了研究长距离交流输电线路上并联电抗器布置对功率传输的影响,基于长距离超、特高压输电线路分布参数等效电路及二端口模型,分析了传输线路的最大传输功率及最大传输效率,推导了串补条件下两种并联电抗器布置方案的级联传输矩阵。采用500 k V、1 100 k V线路典型参数,针对并联电抗器布置对最大传输功率与最大传输效率的影响进行数值模拟分析。研究结果表明并联电抗器位置在发送端与中点串补电容之间或者接收端与中点串补电容之间变化时,最大传输功率与最大传输效率均随其位置变化而发生变化。同时,并联电抗器补偿度也会影响功率传输,随着并联电抗器补偿度的增加最大传输功率及最大传输效率均会降低。
