The issue on short-term optimal dispatch for cascade hydropower stations based on peak/valley output ratio restrictions from the power grid was studied,and the model of short-term optimal operation was established which was then solved by POA algorithm.

The Grey Forecast of Maximum Load and Peak-Valley Difference of Beijing,Tianjin and Tangshan Wire Netting;

In this paper, by using the grey system theory,we set up the grey forecast model of year s maximum electric load and peak-valley difference of shanxi wire netting and the forecast value of year s maximum electric load and peak-valley difference is calculated until 2005.

As the development of grid and increase of peak-valley difference,to satisfy the need of grid,construction of hydropower plants and pumped storage power stations should speed up.

The restoration method of load curve based on peak-valley ratio and the estimation method of central air-conditioning load based on appointed day are brought forward.

With the development of society and economy and the change of the power market, the difference between peak and valley of the Northeast power pool is steadily increasing and the contradiction between supply and demand is becoming increasingly acute.