为了增强直流微电网中分布式储能系统的惯性,并在线路阻抗不匹配的情况下实现各储能单元(energy storage unit,ESU)的荷电状态(state of charge,SOC)均衡,提出一种基于虚拟直流电机(virtual DC machine,VDCM)的分布式储能系统能量动态...为了增强直流微电网中分布式储能系统的惯性,并在线路阻抗不匹配的情况下实现各储能单元(energy storage unit,ESU)的荷电状态(state of charge,SOC)均衡,提出一种基于虚拟直流电机(virtual DC machine,VDCM)的分布式储能系统能量动态分配策略。首先,将VDCM技术应用到储能侧控制中,利用VDCM的输出特性增强系统的抗扰能力。然后,利用电枢回路方程输出特性,并根据储能系统能量分配需求,动态设计虚拟电枢电阻,使其可随SOC在规定界限内自适应变化,实时调整各变换器的输出功率,并引入压降调节因子动态微调各变换器输出虚拟压降至相等,从而补偿线路阻抗的不匹配度,实现各ESU的SOC均衡。此外,采用一致性算法在相邻ESU间获得所需平均值信息,增强系统的可扩展性。最后,搭建光伏多储能直流微电网系统模型,仿真和实验结果验证了所提控制策略的合理性和有效性。展开更多
Heat transfer,friction factor and thermal enhancement factor characteristics of a double pipe heat exchanger fitted with square-cut twisted tapes（STT） and plain twisted tapes（PTT） are investigated experimentally u...Heat transfer,friction factor and thermal enhancement factor characteristics of a double pipe heat exchanger fitted with square-cut twisted tapes（STT） and plain twisted tapes（PTT） are investigated experimentally using the water as working fluid.The tapes（STT and PTT） have three twist ratios（y=2.0,4.4 and 6.0） and the Reynolds number ranges from 2000 to 12000.The experimental results reveal that heat transfer rate,friction factor and thermal enhancement factor in the tube equipped with STT are significantly higher than those fitted with PTT. The additional disturbance and secondary flow in the vicinity of the tube wall generated by STT are higher compared to that induced by the PTT is referred as the reason for better performance.Over the range considered,the Nusselt number,friction factor and thermal enhancement factor in a tube with STT are respectively,1.03 to 1.14,1.05 to 1.25 and 1.02 to 1.06 times of those in tube with PTT.An empirical correlation is also formulated to match with experimental data of Nusselt number and friction factor for STT and PTT.展开更多
文摘为了增强直流微电网中分布式储能系统的惯性,并在线路阻抗不匹配的情况下实现各储能单元(energy storage unit,ESU)的荷电状态(state of charge,SOC)均衡,提出一种基于虚拟直流电机(virtual DC machine,VDCM)的分布式储能系统能量动态分配策略。首先,将VDCM技术应用到储能侧控制中,利用VDCM的输出特性增强系统的抗扰能力。然后,利用电枢回路方程输出特性,并根据储能系统能量分配需求,动态设计虚拟电枢电阻,使其可随SOC在规定界限内自适应变化,实时调整各变换器的输出功率,并引入压降调节因子动态微调各变换器输出虚拟压降至相等,从而补偿线路阻抗的不匹配度,实现各ESU的SOC均衡。此外,采用一致性算法在相邻ESU间获得所需平均值信息,增强系统的可扩展性。最后,搭建光伏多储能直流微电网系统模型,仿真和实验结果验证了所提控制策略的合理性和有效性。
文摘Heat transfer,friction factor and thermal enhancement factor characteristics of a double pipe heat exchanger fitted with square-cut twisted tapes（STT） and plain twisted tapes（PTT） are investigated experimentally using the water as working fluid.The tapes（STT and PTT） have three twist ratios（y=2.0,4.4 and 6.0） and the Reynolds number ranges from 2000 to 12000.The experimental results reveal that heat transfer rate,friction factor and thermal enhancement factor in the tube equipped with STT are significantly higher than those fitted with PTT. The additional disturbance and secondary flow in the vicinity of the tube wall generated by STT are higher compared to that induced by the PTT is referred as the reason for better performance.Over the range considered,the Nusselt number,friction factor and thermal enhancement factor in a tube with STT are respectively,1.03 to 1.14,1.05 to 1.25 and 1.02 to 1.06 times of those in tube with PTT.An empirical correlation is also formulated to match with experimental data of Nusselt number and friction factor for STT and PTT.
