Research On Optimization For Energy Production Units And Collecting And Distributing Networks In Pelagic Islands

Stable,reliable and reasonably priced energy supply,especially electricity supply,is a prerequisite for inhabiting and guarding pelagic islands and ensuring their sustainable development.Due to the geographical distance,the cost of laying cables between the mainland power grid and pelagic islands is extremely high,and more vulnerable to restrictions such as route control.Therefore,almost all pelagic islands are difficult to connect to the mainland power grid,and sustainable energy supply has been a difficult problem for residents' life,garrison electricity and industrial development in islands.Pelagic islands and their surrounding areas have a large amount of renewable energy resources.Maximizing the development of local renewable energy in islands,reducing conventional fuel consumption,and enhancing the selfsustainability of energy resources in islands shall be the vision and long-term goal in terms of the constructing and developing pelagic islands.However,given the uniqueness of pelagic islands in terms of resources,development conditions and energy demand,conventional standalone microgrids are unsuitable for pelagic island clusters.To further improve the proportion of renewable energy in the energy supply system,enhance the self-sufficiency of energy resources and load support capability of pelagic islands,and reduce the demand and frequency of fuel replenishment,following the chain of energy production,transmission and distribution,the energy production units and power collecting and distributing network of pelagic islands are taken as the objects,and several key issues on the energy production and distribution are studied.The main contents include:To improve the flexibility and dispatchability of island energy production units and enhance the operating efficiency of the hybrid microgrid in islands,a hybrid brushless doubly-fed induction generator(HBDFIG)and its optimal scheduling strategy are designed for the purpose of direct distribution of power generation between the AC side and the DC side.First,the structure of HBDFIG is designed.Based on the theory of brushless doubly-fed induction generator,the power characteristic of HBDFIG is modeled.The power distribution capability of HBDFIG under different operation modes together with the analysis of different operating states of the island microgrid are discussed and analyzed.Then,with the goal of minimizing fuel costs,a scheduling strategy is proposed for the coordinated operation of HBDFIG with conventional generation units and energy storage systems to lower the losses of the microgrid and correspondingly reduce island fuel consumption.The effectiveness of HBDFIG and its scheduling strategy is verified with case studies.To make efficient use of renewable energy and maximize the self-sufficiency of the island's electricity and freshwater needs,an optimization method for the configuration of an integrated energy supply system based on the cogeneration of hydro-electricity in concentrating solar power plants is proposed.Firstly,a hydro-electricity model for a concentrationg power plant is designed to achieve a stepwise utilization of energy,and the combined output characteristics of electricity and fresh water are analyzed.Furthermore,a 100% renewable energy supply system with wind turbines,concentrating solar power plant,thermal/energy storage system and desalination plant is proposed,which can make full use of the flexible scheduling ability of the concentrating solar power plant to complement the wind power generation,and reduce the size of the island's battery energy storage configuration by using the thermal storage system.Different from the conventional capacity allocation approach,which finds the minimum levelization cost from finite capacity combinations by enumeration,a mixed integer linear programming model for a 100% renewable energy supply system is developed,and the costeffectiveness of the proposed energy supply scheme for those pelagic islands with abundant renewable energy and affording high fuel costs is verified with case studies.To take into account the need of convenient,green and sustainable power supply for island isolated users,and optimize the structure of the power collecting and distributing network,the characteristics of isolated users and limitations of conventional power supply modes are firstly analyzed,and a power supply mode for isolated users based on the shared multiplexing of mobile energy storage vehicles is proposed.The feasibility and application advantages of this model are also demonstrated.On this basis,a two-stage planning model of the island power distribution network is established.In the first stage,the site selection of switching stations and distribution schemes for isolated users are traversed,and the battery pack demand and the distribution plan in each scheme are optimized to obtain the capacity of switching stations,demand response capacity,and overall costs corresponding to different locations of switching stations and distribution schemes of isolated users.The second stage uses the traversal results of the first stage as the input condition.The island hybrid microgrid network is planned,and the flexible regulation capabilities of HBDFIG and the switching station are highlighted to optimize the power distribution network.Through the combination of the traversal method and precise algorithms,the island power collecting and distributing network is optimized considering the economy and environmental effects.The feasibility of the proposed power supply method for isolated users and the economic advantages of the novel distribution network are verified with extensive simulation results.To realize the joint development of "resource island + load island" and essentially improve the renewable energy efficiency of the island cluster,a hybrid power transmission network consisting of submarine cable and vessel routes is proposed.Firstly,a power transmission route based on power exchange vessels is designed to address the problems of high investment costs and harsh implementation conditions of conventional submarine cable.The power transmission model for the power exchange vessel is put forward based on the navigation characteristics of vessels.The mathematical relationship between the energy storage capacity,transmission power and voyage distance of a single route is deduced.Also,quantitative analysis of cost for single route at different transmission distances and transmission power are carried out.Furthermore,a planning model of the hybrid power transmission network including routes with power exchange vessels is established,and the technical and economic advantages of the hybrid power transmission network are highlighted compared with independent power supply mode and cable network mode.