An Improved Model of Total Supply Capability for Distribution Systems
The Total Supply Capability (TSC) model is newly proposed to evaluate the maximum load a distribution system can supply under the N-1 security guideline. This TSC model and a linear programming algorithm can calculate the accurate TSC of a distribution system; but the results of transformer loading rates calculated by this model are usually unbalanced, which is unacceptable in the practical operation. In order to solve this problem, this paper discusses the solution properties of the TSC model first. It is found that the transformer loading rates vector is not unique under the same TSC level; and only one of the optimal solution can be obtained from the linear programming software such as lingo. Then, an improved TSC model is proposed, which takes variance of loading rates and heavy-load areas into account. This new model is divided into two parts, the first part is the TSC calculation process, and the second part is the most balanced loading rate calculation process. Finally, a practical case is given to illustrate the effect of the improved model. It has shown that the loading rates calculated through this method are more balanced than the original one under the same TSC. The method can be useful tools to help system planners to get the best configuration of transformers in distribution systems.
Evaluation Method for Maximum Load Capability of Urban Medium-voltage Distribution System
A method for evaluating the maximum load capability is proposed to deal with the bottleneck of load capacity in urban medium-voltage distribution system.By analyzing different connection modes for load transfer,a model of the maximum load capability based on N-1 principle is given.The model,taking the maximum load power as objective function,is a mixed integer programming and can be solved by Lingo.The sample of actual distribution system verifies the feasibility and effectiveness of the method proposed in evaluating the maximum load capability,and shows that strengthening connections between substations can improve supply reliability and develop the latent supply capability of distribution system.The proposed evaluation method is promising to be applied in optimizing the operation of distribution system,determining the appropriate loading level of supply equipments and guiding construction of distribution system.
On the Role of Professional Sports in the National Economy Under the Market Economy Conditions
Through the research of the present situations of the professional sports at home and abroad and its influence on economy, this paper points out the opportunities, challenges and the exist- ing main problems that the professional sports faces in the transitional peried-from plan economy to market economy, then elucidates that the professional sports can becompletely developed and improved and play an important role in the national economy under the market economy conditions.