| The interconnection of power systems and economical considerations for reconstructed power systems drive the modern bulk power system to operate at a greater variety of operating points and closer to their operating limits, which brings more concerns of dynamic security analysis of power system. In this dissertation, topological characteristics of practical dynamic security region (PDSR) in complex power injection space and node voltage phase space are studied based on nonlinear dynamic system theories. Effects of on load tap-changer (OLTC) dynamics on voltage stability of power system subject to serious load disturbance are investigated. We also discuss the mechanism of transient voltage stability to give deeper insight of the phenomena. The displacement law of PDSR in complex power injection spaces is found for different proportions of load induction motor. At last, a new method is proposed for on line security monitoring, protection and control, which incorporates SPM from PMU in PDSR of node angle space.First, voltage stability region is studied in state space (tap-rate n and load voltage V) and injection space of power system subject to serious load disturbance. Effects of on load taper changer (OLTC) on transient and long-term voltage stability are analyzed and several conclusions are drawn, including a principle on"critical power disturbance vectors". Based on the principle, a proposition about obtaining boundary of voltage stability region through simulation is acquired and proved. In addition, topological characteristic of voltage stability security region (a critical boundary for a response region in injection space) is obtained.Then, a deeper analysis is given about mechanism of transient voltage stability and instability mode for different proportions of load induction motor. It is pointed that that transient angular instability and transient voltage instability may occur almost simultaneously in some typical power systems. When motor load in the total load is over a certain proportion, a power system may lose transient voltage stability. The higher the proportion of motor and its loading factors are, the more likely transient voltage instability occurs. It is also found the proportion of motor load and generators have great impact on the critical clearing time. Then, the boundary characteristics of practical dynamic security region (PDSR) are studied for severaltypical power systems with different fault locations and different fault durations. It is found that the practical dynamic security region (PDSR) in complex power injection space can be described by hyper-planes. PDSR in complex power injection space is more precise than the one in active power injection space, especially in the studies of power system transient voltage stability. Differences between real boundaries and the approximate critical HP boundaries are addressed in detail and some beneficial results about displacement characteristics of the critical HP boundaries are found, which greatly extends the usages of PDSR.How to make better use of the Synchronized Phasor Measurement (SPM) in the security monitoring, protection and control of power system is a challenging research task. In this paper, the concept of practical dynamic security region (PDSR) in phase angle space is presented. A study on PDSR of power systems shows that critical points satisfying transient stability in angel space can still be described by one or several critical hyper-planes. With its on-line application, stability margins of current operating points in different directions in phase angle space may be obtained. The original system with high dimension is to be reduced to an equivalent system with lower dimension by dynamic equivalent reduction based on coherency. Thus, through PDSR of the equivalent system, whether the original power system will guarantee its transient stability can be identified. In addition, PDSR of equivalent system in angle space provides an effective way to partially equip PMU.
|
PDF Full Text Request