Controlling UEP Method Of Stability Analysis In Network Structure Preserving Power System Model

With the development of economy and the advancement of the technology, the traditional power systems are experiencing a process along the way from the regional power supply to the large-scale connected power systems. This trend brings a great economic benefit, while at the same time, a serious challenge to the stability of the power systems, especially the transient stability. The direct method is one of the most important methods in the transient stability analysis. To Analyze and determine the transient stability of the post-fault system by the direct method is an important task for the research on power systems' stability. Although great progress has been made over the last decades, there are still many problems to be explored thoroughly, such as applications to the network-preserving model, practical applications and so on. The main research work has been developed as follows:Firstly, this paper analyses the external jump behavior in the network-preserving model and gives the BLE method for determining the direction of the external jump. It is very important to acquire the right initial value of post-fault system. Based on the analysis of the external jump behavior, this paper extends the traditional Controlling UEP method to the network-preserving model and presents the new direct method, Extended Controlling UEP method. Compared with traditional Controlling UEP method, this method needs twice comparation of transient energy value before it identifies whether stability will be maintained or lost. Sometimes it also gives the conservative stability assessments. In order to improve the validity and accuracy of ECUEP method, the Hybrid ECUEP method is introduced.Secondly, this paper discusses the effect of TCSC on the transient process and transient stability based on long distance transmission systems using B-H network-preserving model. The simulation shows that the different series compensation degree will possibly result in the change of the critical cutset. Based on this result, this paper analyzes the reason of the change under the guidance of Controlling UEP theory. The reason is that the Controlling UEPs of different post-fault systems are not corresponding. Moreover the distribution of transient energy on lines (cutsets) will not be even because of too large series compensation degree. This will degenerate the transient stability of power system.