直流侧电压的控制是并联型有源电力滤波器(active power filter,APF)的关键技术之一。直流侧电压的大小将影响到APF的功率损耗和补偿性能。而在复杂的工业应用场合,各种负载的波动将会造成APF公共耦合点的电网电压的波动,进而影响到APF...直流侧电压的控制是并联型有源电力滤波器(active power filter,APF)的关键技术之一。直流侧电压的大小将影响到APF的功率损耗和补偿性能。而在复杂的工业应用场合,各种负载的波动将会造成APF公共耦合点的电网电压的波动,进而影响到APF的补偿性能。以三相三线并联型有源电力滤波器为例,分析APF的功率损耗和直流侧电压之间的关系以及补偿性能和直流侧电压、电网电压之间的关系,并提出一种采用下垂调节器来控制直流侧电压指令值的控制策略。当电网电压升高时,提高直流侧电压,从而提高APF的补偿性能;当电网电压降低时,降低直流侧电压,在保证APF的补偿性能的基础上降低功率损耗。仿真和实验结果验证了理论分析,采用下垂调节器能够实现APF功率损耗和补偿性能的综合优化。展开更多
有源电力滤波器(active power filter,APF)是一种动态抑制谐波和无功的电力电子装置,以并联型有源电力滤波器为研究对象,从APF补偿电流的控制和直流侧电容电压角度出发,分析了电源电流控制方式,实现补偿电流的检测及双闭环反馈控制,提...有源电力滤波器(active power filter,APF)是一种动态抑制谐波和无功的电力电子装置,以并联型有源电力滤波器为研究对象,从APF补偿电流的控制和直流侧电容电压角度出发,分析了电源电流控制方式,实现补偿电流的检测及双闭环反馈控制,提高系统的补偿精确度和动态响应性能。另外,直流侧电压的指令值都是根据电网电压的工作范围、APF的直流侧电容、额定输出电流、PWM逆变器输出侧电感、电流电压调节器以及调制策略等参数设计的,在考虑直流侧电压与APF功率损耗和补偿性能关系的基础上,提出了采用下垂调节器设计逆变器直流侧电压的控制参考值,使其兼顾APF的功率损耗及补偿性能综合平衡的优点。仿真结果验证了该APF控制系统的正确性和有效性。展开更多
An alternating current(AC)microgrid is a system that integrates renewable power,power converters,controllers and loads.Hierarchical control can manage the frequency of the microgrid to prevent imbalance and collapse o...An alternating current(AC)microgrid is a system that integrates renewable power,power converters,controllers and loads.Hierarchical control can manage the frequency of the microgrid to prevent imbalance and collapse of the system.The existing frequency control methods use traditional proportion integration(PI)controllers,which cannot adjust PI parameters in real-time to respond to the status changes of the system.Hierarchical control driven by fuzzy logic allows real-time adjustment of the PI parameters and the method used a two-layer control structure.The primary control used droop control to adjust power distribution,and fuzzy logic was used in the voltage loop of the primary control.The secondary control was added to make up for frequency deviation caused by droop control,and fuzzy logic was used in the secondary frequency control to deal with the dynamic change of frequency caused by the disturbances of loads.The proposed method was simulated in Matlab/Simulink.In the primary control,the proposed method reduced the total harmonic distortion(THD)of two cycles of the output voltage from 4.19%to 3.89%;in the secondary control,the proposed method reduced the frequency fluctuation of the system by about 0.03 Hz and 0.04 Hz when the load was increased and decreased,respectively.The results show that the proposed methods have a better effect on frequency maintenance and voltage control of the AC microgrid.展开更多
Purpose： To investigate effects of neuro-immuno-modulation on wound healing by observing changes of cytokines and hypothalamic-pituitary-adrenal （HPA） axis hormones in acute stress reaction in rats with wound and c...Purpose： To investigate effects of neuro-immuno-modulation on wound healing by observing changes of cytokines and hypothalamic-pituitary-adrenal （HPA） axis hormones in acute stress reaction in rats with wound and combined local radiation injury. Methods： Sixty female Wistar rats （weighting 200 ± 20 g） were randomly divided into normal control group, wound group and combined wound-local radiation （CWR） group （25 Gy local radiation post wound）, 20 rats in each group. Contents of IL-1β, IL-6 and IFN-γ and IL-4 in serum were measured and changes of adrenocorticotropic hormone （ACTH） and glucocorticoid （GC） in serum were analyzed by using enzyme-linked immunosorbent assay and radioimmunologic assay, respectively at different time points post wound and radiation. Results： （1） The level of IFN-γ, one of the Thl cell cytokines increased significantly at 14 d post CWIL which was markedly higher than that in control group and wound group. However, the level of IL-4, IL-1β and IL-6, one of the Th2 cell cytokines, did not show obvious change. （2） Ratio of Thl/Th2 （IFN-γ/IL-4） in wound group and CWR group increased significantly at 7 d after wound and radiation, which suggested that Thl/Th2 balance drifted to Thl immune response. The ratio of Thl/Th2 in wound group returned to the normal level up to 14 d after the wound and radiation, while the Thl/Th2 ratio in CWR group increased persistently and was much higher than that in control and wound groups. （3） Level of serous ACTH and CC in CWR group increased at 3 d post wound and radiation, and among them, level of CC showed statistically significant increase, which was much higher than that in control and wound groups. Conclusion： Level of serous neurohormone CC in rats increased significantly immediately after wound and radiation; while the level of IFN-γ showed significant increase only up to 14 d after wound and radiation, and the Th1/Th2 imbalance sustained till 28 d post wound and radiation. In order to reduce acute damage caused by CWR, organic immune system and nerve system showed up a marked regulate effects simultaneously and mutually. Nonetheless, the excessive stress induced by CWR causes distur- bance of immunoregulation, which is one of the key reasons for delayed wound healing in CWR.展开更多
文摘直流侧电压的控制是并联型有源电力滤波器(active power filter,APF)的关键技术之一。直流侧电压的大小将影响到APF的功率损耗和补偿性能。而在复杂的工业应用场合,各种负载的波动将会造成APF公共耦合点的电网电压的波动,进而影响到APF的补偿性能。以三相三线并联型有源电力滤波器为例,分析APF的功率损耗和直流侧电压之间的关系以及补偿性能和直流侧电压、电网电压之间的关系,并提出一种采用下垂调节器来控制直流侧电压指令值的控制策略。当电网电压升高时,提高直流侧电压,从而提高APF的补偿性能;当电网电压降低时,降低直流侧电压,在保证APF的补偿性能的基础上降低功率损耗。仿真和实验结果验证了理论分析,采用下垂调节器能够实现APF功率损耗和补偿性能的综合优化。
文摘有源电力滤波器(active power filter,APF)是一种动态抑制谐波和无功的电力电子装置,以并联型有源电力滤波器为研究对象,从APF补偿电流的控制和直流侧电容电压角度出发,分析了电源电流控制方式,实现补偿电流的检测及双闭环反馈控制,提高系统的补偿精确度和动态响应性能。另外,直流侧电压的指令值都是根据电网电压的工作范围、APF的直流侧电容、额定输出电流、PWM逆变器输出侧电感、电流电压调节器以及调制策略等参数设计的,在考虑直流侧电压与APF功率损耗和补偿性能关系的基础上,提出了采用下垂调节器设计逆变器直流侧电压的控制参考值,使其兼顾APF的功率损耗及补偿性能综合平衡的优点。仿真结果验证了该APF控制系统的正确性和有效性。
基金National Natural Science Foundation of China(No.62303107)Fundamental Research Funds for the Central Universities,China(Nos.2232022G-09 and 2232021D-38)Shanghai Sailing Program,China(No.21YF1400100)。
文摘An alternating current(AC)microgrid is a system that integrates renewable power,power converters,controllers and loads.Hierarchical control can manage the frequency of the microgrid to prevent imbalance and collapse of the system.The existing frequency control methods use traditional proportion integration(PI)controllers,which cannot adjust PI parameters in real-time to respond to the status changes of the system.Hierarchical control driven by fuzzy logic allows real-time adjustment of the PI parameters and the method used a two-layer control structure.The primary control used droop control to adjust power distribution,and fuzzy logic was used in the voltage loop of the primary control.The secondary control was added to make up for frequency deviation caused by droop control,and fuzzy logic was used in the secondary frequency control to deal with the dynamic change of frequency caused by the disturbances of loads.The proposed method was simulated in Matlab/Simulink.In the primary control,the proposed method reduced the total harmonic distortion(THD)of two cycles of the output voltage from 4.19%to 3.89%;in the secondary control,the proposed method reduced the frequency fluctuation of the system by about 0.03 Hz and 0.04 Hz when the load was increased and decreased,respectively.The results show that the proposed methods have a better effect on frequency maintenance and voltage control of the AC microgrid.
文摘Purpose： To investigate effects of neuro-immuno-modulation on wound healing by observing changes of cytokines and hypothalamic-pituitary-adrenal （HPA） axis hormones in acute stress reaction in rats with wound and combined local radiation injury. Methods： Sixty female Wistar rats （weighting 200 ± 20 g） were randomly divided into normal control group, wound group and combined wound-local radiation （CWR） group （25 Gy local radiation post wound）, 20 rats in each group. Contents of IL-1β, IL-6 and IFN-γ and IL-4 in serum were measured and changes of adrenocorticotropic hormone （ACTH） and glucocorticoid （GC） in serum were analyzed by using enzyme-linked immunosorbent assay and radioimmunologic assay, respectively at different time points post wound and radiation. Results： （1） The level of IFN-γ, one of the Thl cell cytokines increased significantly at 14 d post CWIL which was markedly higher than that in control group and wound group. However, the level of IL-4, IL-1β and IL-6, one of the Th2 cell cytokines, did not show obvious change. （2） Ratio of Thl/Th2 （IFN-γ/IL-4） in wound group and CWR group increased significantly at 7 d after wound and radiation, which suggested that Thl/Th2 balance drifted to Thl immune response. The ratio of Thl/Th2 in wound group returned to the normal level up to 14 d after the wound and radiation, while the Thl/Th2 ratio in CWR group increased persistently and was much higher than that in control and wound groups. （3） Level of serous ACTH and CC in CWR group increased at 3 d post wound and radiation, and among them, level of CC showed statistically significant increase, which was much higher than that in control and wound groups. Conclusion： Level of serous neurohormone CC in rats increased significantly immediately after wound and radiation; while the level of IFN-γ showed significant increase only up to 14 d after wound and radiation, and the Th1/Th2 imbalance sustained till 28 d post wound and radiation. In order to reduce acute damage caused by CWR, organic immune system and nerve system showed up a marked regulate effects simultaneously and mutually. Nonetheless, the excessive stress induced by CWR causes distur- bance of immunoregulation, which is one of the key reasons for delayed wound healing in CWR.
