Analysis of electricity purchase risks for grid companies based on historical simulation;

In the interim of the restructure of the power market in China,the grid company should guarantee the security of the operating network and balance the profit of each generation company,thus the electricity purchasing cost related to the practical generation schedule sometimes exceeds the optimal purchasing cost.

By using the optimal power flow(OPF),the relation between the electricity purchasing cost change and the line stability limit which is the product of the stability limit factor and the basic stability limit of the line,is described by the derivative of the augmented lagrangian function with respect to the line stability limit factor.

Normally traditional methods of electricity purchasing cost calculation are on the basis of certain power supply-demand balancing and ignore the uncertainty implied in the operation of power system, thus the analysis results of traditional methods cannot offer overall and valuable references.

Through analysis on the power purchase cost structure,the problems existed in the preparation and execution of power generation plan and the impact of current power generation plan preparation to the power purchase cost of power grid are pointed out.

Unlike other generationplants, its benefit comes from capacity one, which equals to the difference between saleincomes at peak blocks and purchasing costs at valley time blocks.