| At present,in face of the energy and environment situation of the increasing consumption of conventional power generation resources and environmental pollution,renewable energy carries out an increasingly important part in energy substitution.Ocean current power generation is a new type of renewable energy power generation,which transforms the ocean current kinetic energy into electricity through turbines.Ocean current has the advantages of continuous and stable current velocity,strong periodicity and high density in renewable energy,which makes it very suitable to supply power to coastal or island loads nearby.There is a vast sea area in China,with a lot of islands far away from the mainland,so it is of great practical significance to develop island micro-grid with marine renewable energy supply.However,the technology and theory of ocean current power generation are presently in the initial stage,and the related research on island micro-grid is not complete.Based on the background above,the ocean current power generation and island micro-grid with ocean current power generation are taken as the research objectives,and many problems related to the reliability and planning of ocean current power generation and island micro-grid are studied in this paper.The paper is supported by the National Key R & D Program "Multi-energy Power System Complementary Coordinated Dispatching and Control"(2017YFB0902200)and State Grid Co.,Ltd.Supporting Technology Project(same name,SGQHDKYODWJS1700143).Aiming at the system reliability evaluation of power generation with ocean current,a reliability model of power generation system considering the spatial variation of current velocity is established.Based on the integral form of momentum conservation law in the vertical direction below the sea,the influence of wake effect on the current velocity of the three-dimensional distribution of turbine array is deduced,and a three-dimensional wake analytical model is established to obtain the velocity-output relationship of the current generation with temporal and spatial variation.Furthermore,the influencing factors of the reliability of ocean current power generation are analyzed,taking into account the characteristics of generator failure,collection system failure,typhoon weather,and space-varying repair rate.The failure rate and repair rate models of ocean current power generation are established,and the method of system reliability evaluation including ocean current power generation is proposed based on the sequential Monte Carlo method.The effect of current generation on improving the system reliability is verified by the data of an actual current field in the Gulf of Mexico,and the influence of current velocity-depth variation,wake effect,turbine layout change,turbine failure rate change,typhoon weather and other factors on the system reliability is analyzed.Aiming at the determination of location and capacity in the planning of ocean current power station,the three-dimensional layout optimization model of ocean current turbines and cables is established.Firstly,according to the characteristics of three-dimensional distribution of ocean current,the main impact of three-dimensional layout location on cost is analyzed,and the model of installation and maintenance cost of ocean current turbines and submarine cables varying with different water depth is established.Secondly,according to the above spatial variation characteristic of current velocity,the output characteristics of the current turbine for layout optimization are obtained.Furthermore,a two-layer model of three-dimensional layout optimization for the ocean current power station is established.The objective function of upper-layer optimization is to minimize the total cost of the construction and operation and maintenance of turbines and cables.The penalty cost of loss of load is taken into account to consider the reliability requirements of the system in the total cost.The decision variables are the turbine construction location and capacity.After the upper layer gets the turbine layout plan,it is put into the lower layer optimization.The lower layer optimizes the cable construction plan among the turbines to be built,and the objective function is to minimize the investment,maintenance cost and loss cost of submarine cables.The optimal configuration scheme of turbine-cable layout is obtained by iterative solution of upper and lower layer optimization.The feasibility of three-dimensional layout optimization method is verified by a case study.Based on the case,the influence of spatial velocity variation,vertical interval,sea area of layout,load parameter change,installation and maintenance cost model factors on the layout of ocean current power station is explored.In order to improve the reliability of island micro-grid power supply,the ocean current power generation is introduced into island micro-grid planning,and the three-dimensional layout coordinated optimization model of micro-grid including ocean current,offshore wind power and tidal current is established.Firstly,the correlation between ocean current,offshore wind power and tidal current output is analyzed by Copula function,and typical scenarios of combined generation of ocean current,offshore wind power and tidal current are generated.Secondly,because the three sources are arranged in the same sea area,the configuration scheme of the current-wind public power collection system is designed,and the topology optimization configuration model of the public power collection system is established.In the public power collection system,wind and tidal current turbines share the same base,the output of the three kinds of turbines flows into the common bus,and the cable topology is allowed to connect between different kinds of turbines.Finally,a two-layer model of coordinated optimization of the three-dimensional layout of the power generation and collection system of the ocean-wind-tidal-diesel-storage micro-grid is established.The upper layer model takes the minimum total cost of investment,installation,maintenance and loss of load of the power generation and collection system of each station as the optimization objective,and optimizes the turbine number and location to be built in each station.The two lower layer models are micro-grid economic scheduling and the above-mentioned public power collection system optimization.Genetic algorithm is used to solve the two-layer model iteratively.A case of a real island micro-grid is analyzed,and the optimized coordinated layout results of each station are obtained.The influence of ocean current power size and storage capacity on the coordinated layout results is compared,and the cost and benefit of applying ocean current power to island micro-grid are analyzed. |
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