 |
Center for Nonlinear Studies |
For many utilities around the world, there has been considerable pressure to increase power flows over existing transmission corridors, partly due to economic incentives (a trend towards deregulation and competition) and partly due to practical difficulties of obtaining authorization to build power plants and transmission lines (environmental concerns). This consistent pressure has prompted the requirement for extending EMS to take account of dynamic security assessment (DSA) and control. Such extension, however, is a rather difficult task and requires several breakthroughs in measurement systems, analysis tools, computation methods and control schemes. Indeed, on-line DSA, concerned with power system stability/instability after contingencies, requires the handling of a large set of nonlinear differential equations in addition to the nonlinear algebraic equations involved in the static security assessment. The computational efforts required in on-line DSA is roughly three magnitudes higher than that for the SSA (static security assessment). This explains why dynamic security assessment and control has long remained in off-line activity. Hence, current power system operating environments have prompted the need to significantly enhance time-domain stability analysis programs to meet new requirements. In addition, it is becoming advantageous to move transient stability analysis from the off-line planning area into the on-line operating environment. There are significant financial benefits expected from this movement. It appears that there is always significant incentive to find superior approaches for stability analysis and control. The PJM Interconnection has successfully designed and implemented a Transient Stability Analysis & Control (TSA&C) system at its energy management system (EMS). EMS provides a real time snapshot including power flow case data from the state estimator, dynamic data and contingency list to the TSA&C application. For each real time snapshot, TSA&C performed a transient stability assessment against the list of 3000 contingencies, calculated stability limits on key transfer interfaces. TEPCO-BCU was selected as the leading fast screening tool for improving the performance of the PJM TSA system. The TEPCO-BCU software was evaluated for three months in the PJM TSA Test System environment. The three-month evaluation period was chosen to include the scheduled outage season and the summer peak load season. This period historically encountered a wide range of real time scenarios that can happen on the PJM power system. During this evaluation period, both the PJM TSA software and the TEPCO-BCU software were run periodically in parallel, every 15 minutes in the PJM TSA Test System environment. The goal was to evaluate TEPCO-BCU in a real time environment as a transient stability analysis screening tool. This talk will present a comprehensive evaluation of the dynamic contingency screening function of TEPCO-BCU and an overview of the solution methodologies behind TEPCO-BCU. Requirements for an on-line screening and ranking tool for PJM systems are presented and evaluated. This evaluation study is the largest in terms of system size, 14,500-bus, 3000 generators, for a practical application of direct methods. The total number of contingencies involved in this evaluation is about 5.3 million. The integrated package TEPCO-BCU is based on the theory of the controlling UEP method, BCU method, energy function method and BCU-guided time-domain method The controlling UEP method and the boundary of stabilityregion- based controlling UEP (BCU) method will be described at a level sufficient to comprehend the concept of a transient-stability screening program for TSA systems.
Host: Misha Chertkov, chertkov@lanl.gov, 665-8119