As a consequence of interconnections of large power systems electromechanical oscillations appear being known as inter area oscillations. In order to suppress such inter area oscillations, a FACTS device is conceive...As a consequence of interconnections of large power systems electromechanical oscillations appear being known as inter area oscillations. In order to suppress such inter area oscillations, a FACTS device is conceived which is designed on the basis of the analogy between the transmission line model and a longitudinal electromechanical model. The damping action is based on the phenomenon of impedance matching of the transmission line model. Modelling of the overall system, optimal placement and control strategy are being treated. A realistic 420kV longitudinal model and a complex power system model are used for simulation. In the simulation, the time response of this device and the effect of this device even under limiting conditions are studied. The results show that this device suppresses the inter area oscillations effectively.展开更多
Wide area damping controller(WADC) is usually utilized to damp interarea low frequency oscillation in power system. However, conventional WADC design method neglects the influence of signal transmission delay and damp...Wide area damping controller(WADC) is usually utilized to damp interarea low frequency oscillation in power system. However, conventional WADC design method neglects the influence of signal transmission delay and damping performance of WADC designed by the conventional method may deteriorate or even has no effect when signal transmission delay is beyond delay margin, an index that denotes delay endurance degree of power system. Therefore, a new design method for WADC under the condition of expected damping factor and required signal transmission delay is presented in this work. An improved delay margin with less conservatism is derived by adopting a new Lyapunov-Krasovskii function and more compact bounding technique on the derivative of Lyapunov-Krasovskii functional. The improved delay margin, which constructs the correlation of damping factor and signal transmission delay, can be used to design WADC. WADC designed by the proposed method can ensure that power system satisfies expected damping factor when WADC input signal is delayed within delay margin. Satisfactory test results demonstrate the effectiveness of the proposed method.展开更多
By use of the May—September 1980—1986 ECMWF daily data of u,v,r and T at 850 hPa,a comparative analysis is performed of basic features of moisture transportation at seasonal mean,quasi-40-day,-biweekly,and-weekly os...By use of the May—September 1980—1986 ECMWF daily data of u,v,r and T at 850 hPa,a comparative analysis is performed of basic features of moisture transportation at seasonal mean,quasi-40-day,-biweekly,and-weekly oscillations,indicating that the seasonal mean transfer plays a decisive role in the moisture flux over the Asian monsoon region,displaying the integer of the monsoon systems there in character;that the transport related to these tropical intraseasonal oscillations are of equal importance in the monsoon period except the difference in their behaviors,i.e.,the transfer shows considerable relative independence in the South-and East-Asian systems;and that the transport at all these intraseasonal oscillations is found to be feeble at equatorial latitudes with little or no influence on each other for both hemispheres.展开更多
文摘As a consequence of interconnections of large power systems electromechanical oscillations appear being known as inter area oscillations. In order to suppress such inter area oscillations, a FACTS device is conceived which is designed on the basis of the analogy between the transmission line model and a longitudinal electromechanical model. The damping action is based on the phenomenon of impedance matching of the transmission line model. Modelling of the overall system, optimal placement and control strategy are being treated. A realistic 420kV longitudinal model and a complex power system model are used for simulation. In the simulation, the time response of this device and the effect of this device even under limiting conditions are studied. The results show that this device suppresses the inter area oscillations effectively.
基金Project(51007042) supported by the National Natural Science Foundation of China
文摘Wide area damping controller(WADC) is usually utilized to damp interarea low frequency oscillation in power system. However, conventional WADC design method neglects the influence of signal transmission delay and damping performance of WADC designed by the conventional method may deteriorate or even has no effect when signal transmission delay is beyond delay margin, an index that denotes delay endurance degree of power system. Therefore, a new design method for WADC under the condition of expected damping factor and required signal transmission delay is presented in this work. An improved delay margin with less conservatism is derived by adopting a new Lyapunov-Krasovskii function and more compact bounding technique on the derivative of Lyapunov-Krasovskii functional. The improved delay margin, which constructs the correlation of damping factor and signal transmission delay, can be used to design WADC. WADC designed by the proposed method can ensure that power system satisfies expected damping factor when WADC input signal is delayed within delay margin. Satisfactory test results demonstrate the effectiveness of the proposed method.
基金This work is supported by National Division of Critical Major Subjects of Basic Research of China.
文摘By use of the May—September 1980—1986 ECMWF daily data of u,v,r and T at 850 hPa,a comparative analysis is performed of basic features of moisture transportation at seasonal mean,quasi-40-day,-biweekly,and-weekly oscillations,indicating that the seasonal mean transfer plays a decisive role in the moisture flux over the Asian monsoon region,displaying the integer of the monsoon systems there in character;that the transport related to these tropical intraseasonal oscillations are of equal importance in the monsoon period except the difference in their behaviors,i.e.,the transfer shows considerable relative independence in the South-and East-Asian systems;and that the transport at all these intraseasonal oscillations is found to be feeble at equatorial latitudes with little or no influence on each other for both hemispheres.
