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
The chaotic system is sensitive to the initial value, and this can be applied in the weak signal detection. There are periodic, critical and chaotic states in a chaotic system. When the system is in the critical stat...The chaotic system is sensitive to the initial value, and this can be applied in the weak signal detection. There are periodic, critical and chaotic states in a chaotic system. When the system is in the critical state, a small perturbation of system,n parameter may lead to a qualitative change of the system＇s state. This paper introduces a new method to detect weak signals by the way of disturbing the damping ratio. The authors choose the duffing equation, using MATLAB to carry on the simulation, to study the changes of the system when the signal to be measured is added to the damping ratio. By means of observing the phase loots chart and time damin chart, the weak signal will be detected.展开更多
This paper proposes an enhanced noise filtering technique to the Hilbert-Huang transformation technology for the identification of structural systems using vibration measurements. The Hilbert-Huang transformation tech...This paper proposes an enhanced noise filtering technique to the Hilbert-Huang transformation technology for the identification of structural systems using vibration measurements. The Hilbert-Huang transformation technology is a set of superior algorithms non-stationary signals and also for analyzing non-linear and offers increased accuracy for linear and stationary signals. However, the signals are filtered by reconstruction from ＂＇selected＂ intrinsic mode functions （IMFs）, derived from the original signal through the empirical mode decomposition method. The proposed filtering technique offers the criterion for selecting the IMFs using the orthogonalization coefficient. In addition, a simple free vibration modal analysis has been resolved for the evaluation of the modal damping ratio. Through the enhanced filtering, it is possible to increase the accuracy for the estimation of the time-varying system＇s natural frequency and the damping ratio, indicative of the degree of damage, which helps an effective design of a control system.展开更多
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.
文摘The chaotic system is sensitive to the initial value, and this can be applied in the weak signal detection. There are periodic, critical and chaotic states in a chaotic system. When the system is in the critical state, a small perturbation of system,n parameter may lead to a qualitative change of the system＇s state. This paper introduces a new method to detect weak signals by the way of disturbing the damping ratio. The authors choose the duffing equation, using MATLAB to carry on the simulation, to study the changes of the system when the signal to be measured is added to the damping ratio. By means of observing the phase loots chart and time damin chart, the weak signal will be detected.
文摘This paper proposes an enhanced noise filtering technique to the Hilbert-Huang transformation technology for the identification of structural systems using vibration measurements. The Hilbert-Huang transformation technology is a set of superior algorithms non-stationary signals and also for analyzing non-linear and offers increased accuracy for linear and stationary signals. However, the signals are filtered by reconstruction from ＂＇selected＂ intrinsic mode functions （IMFs）, derived from the original signal through the empirical mode decomposition method. The proposed filtering technique offers the criterion for selecting the IMFs using the orthogonalization coefficient. In addition, a simple free vibration modal analysis has been resolved for the evaluation of the modal damping ratio. Through the enhanced filtering, it is possible to increase the accuracy for the estimation of the time-varying system＇s natural frequency and the damping ratio, indicative of the degree of damage, which helps an effective design of a control system.
