Study On Short-term Optimal Scheduling Of Photovoltaic Power And Hydropower Plants Hybrid System Under Different Operation Modes

With the continuous progress and development of society,environmental pollution and energy shortage problems are gradually highlighted,vigorously developing renewable energy and actively promoting the transformation of energy structure is of great significance for sustainable socio-economic development.Photovoltaic(PV)power is easily affected by climate and other factors,and its integration into the power grid alone will pose a threat to the safe and stable operation of the power grid or generate a large amount of power curtailment,through good regulation performance,rapid start-up and shutdown and clean and non-polluting hydroelectric power generation and its joint integration into the power grid can improve the efficiency of renewable clean energy.However,as more PV plants are established,the uncertainty of the output of each PV plant individually will lead to an increase in the complexity of the model and make it more difficult to solve the model.In addition,hydro-PV hybrid systems of different scales have not been studied separately according to their main tasks in the grid,which does not give full play to the power generation capacity of each power plant in the hybrid system.In this paper,we study how to analyze the joint uncertainty of each PV plant in the hybrid system and how to give full play to the power generation and dispatch performance of different scale hybrid systems separately.The main contents are as follows.(1)A random sampling model based on probabilistic sequences is established to generate representative PV output scenarios for the problem of output uncertainty of multiple PV plants in hybrid systems.The model jointly processes the prediction deviation process of multiple mutually independent PV plants through probabilistic sequence theory,and obtains representative PV output scenarios through scenario generation and reduction methods to fully consider the adverse effects of PV output uncertainty on complementary operation.(2)For the different scheduling tasks undertaken by different scales of hydro-PV hybrid systems in the grid,short-term multi-objective optimal scheduling models based on chance-constrained programming theory for small-and medium-scale hydro-PV hybrid systems and optimal scheduling models for large-scale hydro-PV hybrid systems considering grid peaking are established respectively.The small-and medium-scale hydro-PV hybrid system can ensure the tracking of the given load process of the grid,and at the same time make as much renewable energy power as possible into the grid;the large-scale hydro-PV hybrid system mainly undertakes the task of peak-sharing in the grid,in order to reduce the peaking pressure of thermal power and other power sources,and at the same time effectively reduce the negative impact of PV output fluctuations on the safe and stable operation of the grid.In addition,both models take hydropower units as the basic dispatching unit and consider different complex constraints and a large number of PV power input scenarios.(3)Both models consider a large number of input variables and constraints,resulting in both models being stochastic mixed integer nonlinear programming models with complex multivariate quantities.In order to improve their solution efficiency,corresponding linearization strategies are proposed for the nonlinear expressions in different models,and the original models are transformed into mixed integer linear programming models and solved by using a mature and efficient solver LINGO.Different research cases are selected separately and their optimization results are analyzed as can be seen.The maximum power curtailment rate of 1.2%for smalland medium-scale hydro-PV hybrid systems on different typical days is 1.2%,which maximizes the integration of renewable energy into the grid under the premise of ensuring the safe and stable operation of the grid.The minimum peak-to-valley ratio of the large scale hydro-PV hybrid system is 26.3%on different typical days.The hydro-PV hybrid system not only effectively reduces the peak-to-valley ratio,but also makes the residual load curve more smooth.