Optimization Of Daily Operation Of The Power System Considering The Uncertainty Of Wind Power

As a kind of clean and renewable energy, the utilization of wind energy not onlycan achieve the energy-saving and emission-reduction, but also respond to today’senergy crisis. Furthermore, great importance has been continuously attached to windpower technology which is the most promising technology. Due to the fluctuation andvolatility of wind power, large-scale wind power integrated into grid has adverseeffect on power system operation. Therefore, it is meaningful to research on theoptimization of daily operation of the power system considering the uncertainty ofwind power, in order to realize the stable and economic operation of the gird.Based on the block bidding theory, a mathematical model is established toachieve the minimum of the total power purchase cost in the paper. The operationmode of wind power, hydropower(including the pumped storage station) and thermalpower is determined by the day-ahead predicted values of load and wind power. Toapproximately simulate the volatility of wind, the interval of wind power is derivedfrom its predicted value and the forecasting error. Moreover, the coordinatedoperation mode of wind, hydropower and thermal power is adopted to cope with thenature of wind generation. At valley load period, the power output of wind andthermal is used jointly to pump water. A rational wind curtailment should be takeninto consideration when the arrangement of thermal power cannot meet the need ofthe peak load because of the wind power fluctuation. In addition, the minimal windpower obtained by the forecasting interval is in conjunction with the hydropower tosupply the load at peak load period so as to avoid the shortage of the thermal poweroutput caused by the reduction of the wind power.An improved clearing algorithm based on block bidding model is applied tocalculate the total purchase of electricity cost. Meanwhile, hydropower and windpower don’t participate in bidding, the settlement price of hydropower is set by theprinciple of proximity while wind power is set at a fixed price. From the overalleconomic perspective, pumped storage plant，hydropower plant and wind plant aregiven a priority to arrangement. Then, the modified daily load curve is horizontally divided into three blocks，including basic load block，intermediate load block andpeak load block． The power output of thermal units is fixed in each load blockaccording to the price which is submitted by all thermal plants and ranked in order.Simultaneously, the thermal unit commitment is considered in basic load block. Inview of the randomness of the wind, the power output of thermal units is determinedunder the circumstance of the extreme wind power, but also the unit ramp rateconstraint should be checked in the intermediate load block and peak load block inorder to make thermal units have enough power output to adjust. Afterward, the finalbidding queue is formed by adding the power output of hydropower units to the queue.Further, the dividing line between intermediate load block and peak load block isdefined by an optimization process to minimize the total purchase cost.Finally, the example is given to illustrate the validity and effectiveness of themodel and algorithm.