Research On Static Stability Limit Of Power System Based On Measured Trajectory

With the development of the power grid, continual growth of the power load and theaccess of the generators which are activated by new energy, the operational states of thepower system have been very complicated and it gets much harder to monitor thereal-time stability and build a smart grid. With real-time measurement data and theThevenin equivalent, we can monitor the real-time stability of power system. That hasbeen one of the most important research interests for domestic and foreign scholars inrecent years.In this paper, the problems that how to effectively get the equivalent parameters ofthe complicated power grid with online measurement data and how to calculate theequivalent parameters rapidly have been studied in the following aspects:A simple, intuitive model is urgently needed to on-line analyze the stability of themodern power network. The power grid can be simplified with Thevenin equivalent at anod. In this paper, traditional model of the Thevenin equivalent is introduced, and thephysical meaning of every parameter is fully explained. The reason for parameter driftduring the calculation process is that the coefficient matrix may be ill. According to thecharacteristics of the actual operating state of the power network, an improved Theveninequivalent model is presented in this paper. Variable forgetting factor recursive leastsquare estimation technique is applied to estimate online Thevenin equivalent. Theanalysis results of single-load system and IEEE10bus system demonstrate that themethod can be used for on-line tracing the Thevenin equivalent parameters effectivelyand rapidly and be applied in actual power systems.Traditional static stability analysis mostly depends on the data of the power system.It cannot analyze the unknown disturbances effectively. So it has some difficult in on-lineapplication. The paper introduces the basic theory of static stability with the examples ofsingle-machine infinite-bus system and two-machine system. The analysis of themulti-machine system static stability illustrates the difficulties in obtaining the on-linestatic stability limit of multi-machine system, and the biggest difficulty lies in that staticstability domain of power system and transition mode are correlation,we can notaccurate predict operation state of power grid in future. Finally, a dual-port Theveninequivalent model of the two-machine system is deduced from a multi-machine system.And the paper analyzes the approach for tracking the real-time equivalent parameters.Based on the static stability analysis theory of a simple system, a method is proposed toinvestigate the on-line static stability limit of a multi-machine system and expected toon-line monitor static stability level of a multi-machine system.It has been a pressing problem for the current smart grid to establish a real-time monitoring system and investigate the static stability analysis of complex power grid. Onaccount of the characteristics of two-area interconnected power grids, the paper presentsa way to get the on-line static stability limit of the contact line. With the transmissionchannel as the basic unit, and by real-time monitoring of its static stability level, we willget the distribution of the various transmission channels and then the most vulnerabletransmission channel will be found. Case studies in two-machine system and IEEE39system are provided to illustrate the effectiveness of the proposed method.