Study On Damping Control And Monitoring Methods For Inter-connected Power Systems Based On WAMS

In order to realize ideally resource dispatch, China is carrying through the construction of the grid. With the application of nation-wide power grid interconnection and China's power transmission from the West to the East, a national hybrid AC/DC power grid will be formed in the future. On one hand, this will bring some technical problems, such as low frequency oscillation which has been the bottleneck of improving the power transmission. On the other hand, with the progress of the wide area measurement system(WAMS) technology, we get new chance to improve the control of modern power system. This work of thesis is going on under such background, and the main works are organized as follows.Firstly, the idea of extended residue ratio(ERR) is brought out to choose the best global signal or its combination as the input of the damping control. The paper deduce the principle of the ERR based on the controllability and observability. The test signal method is adopted here to calculate the ERR when dealing with a big system.Secondly, the SVC is introduced here to be utilized to damp the oscillation with the global signal as its control input. The principle of the SVC supplement damping control is discussed. The ERR is adopted to choose the best control input. According to the pole placement method, the time constant and the gain of the controller are determined. Time domain simulation and small signal analysis on several examples testify the effectiveness of the supplementary controller.Thirdly, the VSC-HVDC supplementary controller with the global feedback signal is designed. After study of the VSCDCT model of the PSS/E, the validity is proved. Then the global damping controller is designed based on the ERR. According to the pole placement method, the time constant and the gain of the controller is determined. The act of the controller is tested based on an example.Fourthly, a supplementary damping controller of HVDC is suggested based on sliding mode control and fuzzy control theory. The switch surface of the sliding mode is determined online by the WAMS. According this a fuzzy logic rule set is formed. The controller acts well according to the rules.Fifthly, the time delay system stability theory is introduced in the controller design process to accommodate the time delay during the transmission of the global signal. The low order system is deduced, and the controller parameters are calculated by the LMI method.Lastly, the main frame of the modern low frequency oscillation monitor and control center is built up according to the real engineer need. The low frequency oscillation is monitored online according to the ESPRIT and Prony analysis method. An adaptive arithmetic is suggested which can determine the model order during the identification process. In this way both the identification accuracy and the speed can be compromised. The arithmetic is tested on some cases.