Research On Capacity Optimization And Operation Control Of Island Renewable Energy Microgrid

Faced with multiple pressures from energy scarcity,population growth,climate change,and international relations,governments and international alliances have turned their attention to the oceans and seas.The ocean is rich in oil and gas deposits,mineral resources,biological resources,and inexhaustible clean marine energy,which will be an important guarantee for human survival and sustainable development in the future.With the strategy of "Maritime Power" gaining unprecedented importance at the national decision-making level,the ocean is playing an increasingly important role in China’s politics,military,economy,scientific research,sustainable development and many other fields.Islands are key platforms for exploiting marine resources and exploring strategic ocean space.Power supply to islands is a basic requirement for ocean development.Therefore,it is significant to study clean,low-carbon,and reliable microgrids for islands.An island microgrid is an environmentally friendly,highly autonomous and flexible dedicated energy system that integrates power supply,power transmission,power consumption and energy storage.It includes distributed renewable energy sources with different characteristics,diversified grid structures,and variable load requirements.The operating characteristics and control strategies of each component of the system are very complex and include numerous key variables and uncertain factors.The research in capacity planning,dispatching method and cooperative control strategy of a microgrid is very different from that of a conventional power system.In this paper,the characteristics of the independent island renewable energy microgrid are analyzed.Considering the special geographical location,resource advantages and comprehensive power supply requirements of the island,the main technical problems such as capacity allocation optimization,dispatch operation optimization and cooperative control method of the island microgrid are thoroughly researched and discussed.The main research contents include:(1)The combination of distributed generation in an islanded renewable energy microgrid and the appropriate size of each component are the key factors that determine the technical and economic feasibility of the grid.Based on the assessment of renewable resources in the target island area,this paper constructs a hybrid island renewable energy microgrid that includes distributed photovoltaic systems,offshore wind turbines,tidal current turbines,battery storage units,and diesel generators in an independent marine context.Considering reliability,energy cost,and resource utilization,a multi-objective capacity optimization method for an islanded renewable energy microgrid is proposed.Three optimization objectives are established:Minimizing the Loss of Power Supply Probability,the Cost of Energy,and the Dump Energy Probability.A hybrid multi-objective gray wolf optimizer based on low differentiation sequence and social motivation strategy is proposed to solve the optimal component size.Simulation results confirm the feasibility of the proposed multi-objective capacity optimization method and lead to an optimal solution set for the capacity allocation of the island energy system.In addition,this paper also compares and analyzes the impact of tidal current power generation on system configuration and optimization objectives in the proposed microgrid.Based on the resource evaluation and the trade-off between multiple objectives,tidal current power generation is suitable to reduce the scale of system capacity and reduce the operation of energy storage units and diesel generators,which can provide a reference for the design of the lowcarbon offshore island microgrid.(2)The operation optimization of an islanded renewable energy microgrid can reduce system operating costs,improve system stability,and promote local renewable energy consumption.Aiming to meet the demand for green and sustainable energy supply for electricity,fresh water,and transportation on the island,this paper proposes a multi-objective operation optimization method for an island renewable energy microgrid that considers electric vehicles and seawater desalination plants as controllable loads.Given the requirements for economic,stable,and low-carbon operation of the island microgrid,an operation optimization model is established that considers the two mutually exclusive objectives of comprehensive operating cost and net load fluctuation,and an effective cooperative operation strategy for power source,energy storage,and load is proposed.To solve the operation optimization problem,an improved multi-objective grey wolf optimizer based on convergence factor,difference strategy and elite selection strategy is proposed.Simulation results confirm the feasibility of the multi-objective operation optimization method and lead to an optimal dispatch operation scheme for an islanded renewable energy microgrid.The comparison of the operation simulations of four different cases verifies that the participation of electric vehicles and desalination plants in the load-side scheduling can effectively reduce the comprehensive operation cost and net load fluctuation.In addition,this paper also compares and analyses the influence of electric vehicles and desalination plants on the optimization objectives of the system.(3)An island microgrid contains a variety of distributed generators and loads with different characteristics and sizes,and usually has a high renewable energy penetration.Most system components are connected to the grid via electronic devices.The system has low inertia,rapid frequency changes,and complex dynamic characteristics.In order to cope with the fluctuation of renewable power generation and the random injection of loads,a flexible and effective operation control method must be employed.Based on the prospect of low-carbon development and the need for electrified transportation on the island,a new fully distributed cooperative control method based on multi-agent consistency theory is proposed for the island microgrid with integrated charging and discharging control for electric vehicles.This method can solve the problems of frequency synchronization and economic operation of the system by the twolayer control of the microgrid.Only the information exchange between neighboring nodes can realize the distributed cooperative control of the system and does not rely on centralized control.The global asymptotic stability of the method is demonstrated under the constraints of charge/discharge rate and SOC.The proposed distributed cooperative control method is verified by case simulation analysis.In various operation cases,the elimination of system frequency and the optimal distribution of electric vehicle charging power under several constraints are achieved in a limited time,and the economic and stable operation is realized.