Application Of Piecewise Linear Approximation Method To The Optimal Scheduling Of Cascades Hydroelectric Plants

Facing the emergence of global energy crisis, non-renewable energy depletion and theincreasingly tense power supply, China pays lots of attention to sustainable development,which is actively adjusting energy structure, taking precedence over hydropowerdevelopment and implementing energy saving strategies.Hydropower is a kind of high quality, green, clean, renewable resources. The jointoperation of cascade hydropower stations can make full use of water resources. It can notonly take advantages of the regulation function of large reservoir, improve the flood controlcapacity of the basin as a whole, but also can save operating cost and liberate productivity.There are close hydraulic and electric relationships in Cascade hydropower stations, andthe generation benefit of each station is influenced by the upstream and downstreamstations greatly. The dispatch and generate head downstream are restricted by upstreamstations while the generate head upstream is constrained by backwater downstream. Thus,the optimal operation of cascade stations is a large-scaled, dynamical, time-lagged andnonlinear problem.This paper first briefly reviews the background of hydroelectric energy developmentand presents the current situations and utilization of hydroelectric energy in China. Underthe contrasting of cases in short-term optimization of step hydroelectric stations indomestic and overseas, we summarize some popular theories and methods adopted inoptimization of step hydroelectric stations in the latest decades and prefer to use linearprogramming to address this issue. Firstly, we translate the nonlinear constraints into linearconstraints via piecewise linear approximation and transform the nonstandard linearprogramming model into standard ones by0-1integer programming. Then, both the headmodel and generation models are generated by interpolation and fitting calculationaccording to the given historical observations. At last, the results of an application inDaYingjiang three step electrical stations using this procedure are given to illustrate the proposed technique. C++program is used to calculate the output power and generate astandard linear program model. And then, this model is solved by lp_slove using mixedinteger linear program which give out a new way to handling the short-term optimization ofstep hydroelectric stations.