Yusheng Xue

A simple direct method for fast transient stability assessment of large power systems

A method for online transient stability assessment of large power systems is proposed. It consists of: replacing the multimachine system by a two-machine dynamic equivalent, further amenable to a one-machine-infinite-bus system; reducing the stability problem to a sole algebraic equation, devised from the equal area criterion, or equivalently from the Lyapunov direct criterion; and using this equation to derive one-shot stability analysis strategies. A technique for system admittance matrix reduction is developed that proves efficient, especially for large systems and multiple-contingency evaluation. The methods main appeal is rapidity: it is about one order of magnitude faster than the most efficient direct criterion. Other attractive features are flexibility and ability to encompass various simulation conditions. Extensions to online sensitivity analysis and control are suggested. >

Extended equal area criterion justifications, generalizations, applications

The extended equal area criterion (EEAC) for online transient stability analysis is considered with the following objectives. The first is to state systematically its main hypotheses and key conditions, justify the former, and suggest means to guarantee the latter. The identification and error analysis of critical machines are among the investigated issues. The second is to scan all possible types of instabilities likely to arise in practice and devise means to treat them. The extension of the EEAC to cases beyond the so-called first-swing stability makes it more robust than all direct methods developed up to now. The third objective is to extract essential information out of a large body of simulations and show that the above improvements and extensions enhance the EEAC accuracy and its capability to work properly even under stringent conditions. Possible EEAC applications are also discussed, and uses of the method as such or as an auxiliary technique for more sophisticated approaches are suggested. >

DIRECT CRITERIA FOR STRUCTURE PRESERVING MODELS OF ELECTRIC POWER SYSTEMS

Abstract Structure preserving models allow constructing interesting Liapunov (or Liapunov-like) functions of the energy type. But their actual application has been stopped because of the difficulties to properly define stability domain estimates. In this paper, practical estimates, previously proposed for the classical reduced network model, are considered, improved and adapted to the above family of functions. Computational questions raised by these direct criteria are further answered. Simulation results and observations are reported, and tradeoffs are discussed.

Hybrid Extended Equal-Area Criterion for Fast Transient Stability Assessment with Detailed Power System Models

Abstract The use of fast direct methods to evaluate the stability of power systems can benefit planning studies and operation planning. The existing Extended Equal-Area Criterion (EEAC), developed in 1988, enabled calculation much faster than timedomain simulations, but failed to deal with large and detailed dynamic systems. Based on it, we propose a new method, which is a Hybrid Extended Equal-Area Criterion (HEEAC), where time-domain simulations are used with a stability assessment provided by EEAC. HEEAC discriminates critical from non-critical machines, and yields a set of stability indicators such as critical clearing times, power transfer limits or power generation limits. The method has been applied to the French EHV system, with detailed generator and load models. The perfonnances are good both in tenns of computing speed and accuracy.

Dynamic Extended Equal Area Criterion- Part 2. Enlbeclding fast valving and automatic voltage regulation

Enibedding fast valving (FV) and automatic voltage regulation (AVIt) in the dynamic equal-area ciiterion (DEEAC) is considered to be a great asset to the neth hod, in paiticular for its on-line use. In this paper we consider FV and AV11 curves to be furnished by a time-domain numerical piograrn, then embed theni in tlie orie-iriachine-infinite-bus equivalent via appropriate transformations. Tlle way of obtaining these curves is not tlie main concern of this pragmatic approach. Rather, what matters here is to exploie whether the approach has potential, i.e. wlietlier the DEEAC thus augmented is still able to preserve accuracy and coniputing speed similar to those of the basic DEEAC. The first siniulation iesults reported in tliis paper show the feasibility of the approach and anticipate good perfoiinances.