Li Wenyuan

A minimum cost assessment method for composite generation and transmission system expansion planning

Composite generation and transmission system expansion analysis should take into account both economic considerations and adequacy requirements. An optimum expansion plan should achieve the minimum total investment, operation and damage cost. A minimum cost assessment method for composite system expansion planning, which can be used to consider generation expansion and transmission expansion simultaneously, is presented. The minimization model proposed to incorporate both operating and outage costs can recognize different customer damage functions at different load buses and includes the duration of the simulated contingency system states . A computer program based on the presented method has been developed to provide a set of line, load bus, generator bus and system indices which can be used to select optimal expansion plans at different load growth levels. Case studies in which the method is applied to the IEEE Modified Reliability Test System indicate its effectiveness. >

A novel method for incorporating weather effects in composite system adequacy evaluation

The proposed method can recognize regional weather aspects including those situations in which transmission lines traverse several geographical regions which undergo different weather conditions. The method uses a Monte Carlo approach which can be readily applied to large-scale transmission systems. Case studies conducted using a program developed at the University of Saskatchewan show that neglecting all consideration of weather effects can lead to an optimistic assessment of system adequacy while ignoring regional weather conditions can result in overestimation of the resulting failure bunching effects due to adverse weather. The effects of weather variations on annualized indices are discussed, and the need to establish suitable and practical procedures for collecting adverse weather data which can be utilized in realistic composite system adequacy assessment is addressed. The modeling procedure also provides a realistic framework for practical data collection. >

A successive linear programming model for real-time economic power dispatch with security

Abstract A successive linear programming model with penalty terms for solving real-time economic active power dispatch with security is presented in the paper. It maintains the advantages possessed by the linear programming model, that is, rapid calculation, reliable convergency and easy treatment of the N and N — 1 line-security constraints. At the same time, it settles quite accurately the problem of the non-linear cost characteristic by incorporating the differential loss coefficients into the successively linearized objective function. A fictitious generation variable is introduced at each load bus and penalized in the objective function. This, on the one hand, guarantees the solvability of the successive linearization from beginning to end. On the other hand, if there exists a non-zero fictitious generation by the end of the iteration, it indicates that load-shedding is indispensable, and thus we get the optimal position and the value of the load-shedding. The calculation results of the IEEE 30-bus system are given. These results demonstrate that the presented model has the same accuracy as the two non-linear models, while it needs much less computing time.

An on-line economic power dispatch method with security

Abstract This paper presents an on-line economic power dispatch method with security; it maintains the advantage of rapid calculation possessed by the classical dispatch approach and at the same time settles N and N — 1 security problems. The calculations are divided into two stages. The optimality of the problem is first obtained and then the feasibility is satisfied on condition that the optimality remains. No slack bus is concerned with, the on-line problem is considered, the storage requirements are small and computational accuracy is sufficiently high. The results of the IEEE 30-bus system are presented in order to demonstrate the efficiency.

Consideration of multi-state generating unit models in composite system adequacy assessment using Monte Carlo simulation

Presents a Monte Carlo method for reliability evaluation of large-scale composite generation-transmission systems. The method is based on combining the basic random sampling technique with a direct analytical approach for system analysis, and the utilization of a minimization model for load curtailment. The technique is particularly suited to simulating large-scale systems and multiple states of generating units. Many utilities are now using multi-state models to assess capacity adequacy. The utilization of multi-state models in a composite generation and transmission study can create considerable computational difficulties when a conventional contingency enumeration approach is used. The Monte Carlo method can be used to assess the effects of multi-state modelling in composite system adequacy assessment. The technique is illustrated by application to two test systems in order to demonstrate the effectiveness of the method.