| Low frequency oscillation phenomena occur much frequently, and cause damage to stable operation of the power system. Wide-area measurement system (WAMS) can be used to restrain low frequency oscillation in the power system, and improves stability of the power system. Using wide area measurement signal as input signal of damping controller to restrain low frequency oscillations becomes a new research idea.Transmitting the wide-area measurement signal via communication networks will introduce time delays. These will affect the stability of the control system. Therefore, the influence of time delay must be considered while designing damping controller based on the wide-area measurement system. At present, using the wide-area measurement signal to restrain low frequency oscillation is researched by many scholars. This research has important theoretical significance and practical application value. Based on this research topic, the main content of this thesis includes the following parts:In the first part of this thesis, the structure of the wide-area measurement system (WAMS) and the main idea of networked control system(NCS) are analyzed. Damping controller is designed using the idea of NCS. Source of time delays in networked control system is elaborated.In the second part, the power system model is established to simulate power system low-frequency oscillation. Concrete schedule of low frequency oscillation suppression is introduced, too.In the third part, the stability of the time-delay system is analyzed based on Lyapunov stability theory. The LMI method is utilized to solve the problem of time delay and ensures system stability margin. Considering the delay stability margin, damping controller based on the wide-area measurement signal is designed to restrain the low frequency oscillation.In the four part of this thesis, according to the longest time-delay, the method of LMI is utilized to design a state-feedback controller based on wide-area measurement signals. |
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