Optimal Modeling And Application Research Of Multi-basin Hydropower Station Group For Provincial Power Grid

With the increase of the hydropower station group scale in provincial power grids,the optimal operation of multi-basin is becoming intricate and facing urgent challenge.There are more requests to construct the reliable and applied model for the optimal operation of multi-hydropower stations because of the complicated optimal computational process which featuring by high-dimensional,strict restrictions,nonlinear and multi-phase characteristics. The intelligent algorithms,which have the fixed shortcomings of complex model structure, difficult preferences,stochastic optimal results,are hard to apply in practice.Nevertheless,the classical conventional optimal algorithms will face the "disaster-dimension" with the increasing variables.It is vital to construct a available optimal model for large scale operation hydropower stations.Moreover,the unit maintenance and power balance in power grids,as the previous condition and the method of verifying rationality for the optimal results respectively,are very complicated.It is very hard to satisfy the increasing requirements by traditional experience and management mode.In this paper,based on the project background of power grids in Yunnan,Fujian and Guizhou,the practical optimal problems including hydropower stations optimal operation,large scale units maintenance scheduling and adjusting discharge peak by hydrothermal plants are studied in-depth.The main contents and research progress are as follows:(1) For the situation of insufficient reserve capacity in many power grids at present,a minimum model for energy shortage is designed to optimize the unit maintenance scheduling. Based on equivalent reserve capacity method,the presented model can ensure the grid safety by adopting the objective of minimum energy shortage and putting the equivalent load curve from unit maintenance scheduling under the system capacity curve.The optimal result can be obtained through combining the heuristic search method(HSM) with the successive approximation method(SAM).The result gained from HSM is specified as the initial feasible solution in SAM and the optimal result meeting all constraints is achieved by iterative calculation.The experimental results of 175 units at Yunnan power grid indicate that the proposed model is more efficient in practical application.(2) In order to meet the complex requirements in hydropower stations optimal operation, a hybrid optimal model consisted DPSA,DDDP and POA organically with the system constrain of up-down bound is presented.The model is seized of the advantages including decreasing the number of hydropower stations by DPSA,minifying the discrete states by DDDP and reducing the computational time by POA.Using the directed-graph to describe the intricate topology of multi-basin,the model can obtain the calculating order quickly by the DFS method in the directed-graph and can calculate all the hydropower stations easily. Finally,the results of the Fujian hydropower system which consists of 44 hydropower stations show that the model can avoid the "dimension-disaster" and the trouble of complicated restricts.Furthermore,the optimal results are very satisfied.(3) With the demand load increasing,the gap of day-energy and the difference open-off in thermal units between two days become larger and larger.Accordingly,it will consume more fuel and it is very difficult to schedule in hydropower system.A medium-term generation model for the peak-power maximization is presented.In order to smooth the rest load curve for the thermal plants and saving the fuel,the model ensures the hydropower stations to fit the gap of system load curve.To achieve the results of the model,all the hydropower stations are classified into two types according the regulation and position in the drainage basin at first.Then the work location which will be as the initialization of HA is decided by the method of load shedding and the water balance is ensured through calculating water depending on power generation.Finally,the results of flood season and dry season in the Fujian hydropower system which consists of 19 up week-regulation hydropower stations show that the model is effective.(4) Thermal power plants should participate in adjusting discharge peak of power system in order to reduce or eliminate the water spill of hydro power plants in flood season.An improved algorithm of adjusting discharge peak of power system by thermal power plants is developed for eliminating fluctuating loads of thermal powers.This algorithm adopts the basic framework originated from the method of load shedding and appends the restriction conditions on loads when cutting system discharge,therefore avoiding difficult judgment in the normal method of electric power and energy balance algorithm and decreasing open-off frequency of thermal power plants.Furthermore,the method has not only ensured the difference on two neighbor hours less than the rising rate of thermal power plant,but also produced the uniform loads.The application results of Yunnan electric power system show that the present method is more reasonable and easily meets the demand of adjusting discharge peak.(5) China's hydropower system,after nearly 20 years development,has formed a trans-basin,large-scale hydropower stations operation system,with complex scheduling relations and requiring a variety of methods and techniques to solve.Therefore,it is vital to construct a large scale operation hydropower system which is scientific,efficient,convenient, and available for practical system.On the background of the success experience in design and developed optimal operation systems in several provincial power grids,this paper puts forward a spatio-temporal resolution to solve the optimal operation problem of complex trans-basin cascade hydroelectric power stations.It based on analyzing the existed optimal operation technology and uses computer science as well as artificial intelligence.The resolution includes directed-graph technology to describe the topology of cascade hydropower stations;smart memory and script control technology to set the restrictions automatically; interface programming and the same model in MVC to handle the linkage between table and chart and multi-reservoir operation.The mid-long term runoff prediction system,long,medium and short term optimal operation system and real-time operation system which adopting these technologies have been applied successfully in provincial power grids of Fujian,Yunnan and Guizhou.Finally,a summary is given and some issues to be further studied are discussed.