Study On The Optimal Capacity Allocation Of Photovoltaic System And Storage For Utility-scale Hydro-photovoltaic Plants

The most striking features of the solar energy are its intermittency and instability resulting from environmental influence.Combination of different solar trackers can be a feasible choice to stabilize output fluctuations.The main aim of this study is to search for the optimal capacity allocation of multiple solar trackers and storage capacity.In this regard,a multi-objective optimization model and an energy storage method are developed.The largest and most complete research base for photovoltaic modules and system operation modes in the world-the Gonghe Photovoltaic Demonstration Base is considered as the case study.The main research contents and results of this paper are as follows:(1)On the basis of summarizing the domestic and foreign scholars’ theory of photovoltaic power generation,the paper analyzes the solar radiation model and the photovoltaic module model.The Perez model used for solar diffuse irradiation calculations predicts that the irradiance is the most accurate.The simulation results of photovoltaic modules show that temperature and light intensity are the two main factors affecting the output characteristics of photovoltaic modules.(2)The photovoltaic output characteristics of the hydro-photovoltaic complementary power plants are analyzed.The vertical dual-axis tracker has the largest annual power generation compared with the fixed-tilt panel,with an average power generation gain of 28.4% under typical weather conditions.In all solar tracking systems,the lowest average volatility is the horizontal-axis bifacial tracker,which is 11% lower than the fixed tilt panel.The output power of string PV inverters with different specifications is within 3%,which has little effect on the output characteristics of PV power plants.(3)In this paper,the calculation method of complementary coefficient between 0~1 and the initial selection method of photovoltaic tracking system are proposed.The optimal capacity allocation method of multiple solar trackers of a photovoltaic power plant considering economic and volatility objectives and a multi-objective optimization model are proposed and solved by genetic algorithm.After the optimal capacity allocation,the ratios of the four types of horizontal-axis bifacial tracker,fixed-tilted bifacial panel,vertical-axis 30° tracker and dual-axis tracker were 51.40%,34.46%,10.27% and 1.17% respectively.Compared with the individual trackers when operating separately,the fluctuations in the optimal capacity allocation are reduced by 16.02% to 38.20%,effectively improving the power quality of photovoltaic generation.The optimal capacity allocation is sensitive to the feed-in tariff and automatic generation control allowable adjustment range.(4)A method for calculating the energy storage capacity considering the power curtailment conditions and the storage and discharge mode is proposed.Different power curtailment conditions correspond to different annual power storage and cycle times.When the power curtailment conditions of photovoltaic power plants with 100 MW installed capacity is 50% of the installed capacity of photovoltaic power plants,the annual storage capacity is up to 58442 MWh.In practice,the optimal energy storage capacity should also be determined based on financial ability,the expected utilization level and the lifetime of energy storage.