Research On Key Problems Of Microgrid Control Strategy And Its Energy Storage System

Because of energy crisis and environmental problems,the microgrid becomes one of the focus of the smart grid research,which is the most important utilization of the solar and wind energy.As the core device of the microgrid,the performance of the inverter control strategy influences the intensive research of the microgrid technology directly.In order to smooth the intermittency,the randomness,and the fluctuations of photovoltaic power grid,it is necessary to allocate the energy storage device in the microgrid.Based on the research of the inverter control strategy,the paper places emphasis on the optimal allocation of the micro-source,the key technical issues the optimal allocation of energy storage,and the heterogeneous energy storage in the microgrid.A set of micro grid experiment platform is set up,which is composed of wind turbine,the PV,and the energy storage devices,to verify simulation result.The main jobs of this thesis are as followed:(1)In the microgrid island modes,the virtual impedance is introduced to ensure the output impedance is inductive under different control parameters of the voltagecurrent double closed-loop controller.The frequency and voltage secondary regulation shifts droop control curves up to decrease frequency and voltage static error.In the grid mode,the current feedback of the inverter is introduced as the outside loop control data to increase damping coefficient,to improve the stability,and solve the problem of resonant peak.(2)Under source-load uncertainty,the method of probability analysis is applied to build the probability model about wind and photoelectric output power,the total load uncertain model and the principle of energy storage in hybrid ratio.The vector ordinal optimization is adopted to get optimal solutions from Pareto optimal solutions under forecast scenario and avoid local optimum.(3)To enhance the photoelectric consumption,he unit combined analysis method is adopted to optimize the energy storage system and stabilize the fluctuation and intermittence of the PV output.To coordinate operation between the grid-connecting photovoltaic power station and energy storage system,the multi-scenario analysis method is employed to build a multi-scenario,high dimension security constrained unit commitment model which considers the coordinated operation between the photovoltaic and energy storage.The Benders decomposition algorithm,which can resolve the large-scale optimal problems,divides the multi-scenario into sub-problems and resolve them respectively.So,the calculating speed is enhanced and the robust is improved.(4)For the difference of the charge-discharge capacity,the charge-discharge rate,the life cycle consistency、the compatibility and other issues of the for the super capacitor,the lithium battery,the lead-acid battery and other types of energy storage devices.Those problems restrict the development of distributed photovoltaic energy storage technology.The parameter stray impedes the development of the heterogeneous system.The heterogeneous energy storage integrated energy management system is established from the heterogeneous energy storage system model,the energy conversion mechanism,and the integrated energy management unit.The multi time scale coupling mechanism,the decoupling control method and other aspects,a hierarchical control strategy for multi time scales of energy storage system is presents to resolve the problem of multi type energy storage heterogeneous in the distributed generation system.The paper focuses on the control strategy and the energy storage of the microgrid.The research result provides the useful theory and experimental data for the microgrid technology。The research result provides is a feasible solution to the large-scale deployment of the renewable energy,the consumption of the renewable energy.The research result has potential value of both theory and application.