Research On Key Technologies Of Ac / Dchybrid Microgrid

In view of the growing global demand for electricity,in order to reduce the total carbon emissions while increasing the demand of power generation,the concept of renewable energy has been proposed.Most of microgrids are AC microgrids in today,and their advantages and disadvantages in control technology and stability assessment have been confirmed by a large number of studies in various literatures.Then people began to investigated DC microgrids.As the technology matured,A hybrid microgrid-AC / DC hybrid microgrid that combines the advantages of both AC and DC microgrids is introduced.However,due to the electronic devices lack of inertia power,especially in island-type hybrid microgrids,AC / DC hybrid microgrids as a weak system with low inertia,pose a threat to control and stability of the system.The reasonable operation of the network proposes corresponding control strategies,which needs further research.In this paper,apply MATLAB / Simulink simulation platform,used to model the distributed energy modules in hybrid microgrid,and study the operation control strategy of the hybrid microgrid,so that the hybrid microgrid can run stably in grid-connected and island mode.It works as follows:First,the operation control strategies of AC / DC hybrid microgrids has been introduced,which are master-slave,peer-to-peer and hierarchical control strategies.Combined with the structure of hybrid microgrid in this paper,the operation of grid-connected and island mode has been described and the corresponding operation strategy has been introduced.Secondly,distributed independent power sources model of AC-DC hybrid microgrid are analyzed.During independent operation,the maximum power point tracking(MPPT method)is applied to photovoltaic power generation to maximize the amount of renewable energy generation.The output characteristic curve of the module is studied to prove the effectiveness of the model and simulation.The working principle of the super energy storage unit is researched and the internal voltage is discharged to maintain the bus voltage balance when the internal power is insufficient.Finally introduced the permanent magnet synchronous wind turbine generator in two-phase synchronous rotating coordinates mathematical model,studying the relation between wind speed and output power,prove its validity by simulation..Thirdly,the improved artificial ant colony algorithm is used to optimize the distributed capacity of the distributed generation(DG)modules.Considering the problems of equipment investment,fuel loss and bidirectional converter loss,then established functions and constraints and algorithm cases are performed.Analysis.Determine the priority and operating conditions of DG based on the improved ant colony algorithm,and iteratively calculate the optimal configuration method in the corresponding constraint domain of the objective function.In this paper,the improved artificial ant colony algorithm is used to improve the convergence of the optimal calculation,which is very suitable for study of nonlinear programming problems.Finally,in order to solve the problem of energy collaborative control of hybrid microgrids,focus on improving the control method of converter,apply a control method based on virtual synchronous machine(VSM).Firstly,a suitable VSM type was selected from the perspective of power quality and system stability.Secondly,the autonomous operation of bidirectional ac / dc converters(BADC)based on dual droop control was proposed and combined with the swing equation of the VSM controller.To ensure the accurate power exchange management between AC and DC subsystems.The power variation in the hybrid microgrid divided into four cases to research.When changing from island mode to grid mode,a pre-synchronization control based on PI has been designed in order to reduce the impact of BADC during the conversion process.Finally,the reliability of the above method was verified by Simulink simulation.