| The development of clean energy is the main measure to deal with the problems of natural resource consumption and environmental pollution in traditional power generation.The promotion and application of renewable energy such as wind and solar power has accelerated the process of energy transition.However,the power generation of renewable energy which has strong volatility and intermittency is generally affected by environmental factors,in order to reduce the adverse impact of the renewable energy on the operation of the grid,it is combined with hybrid energy storage system(HESS),loads and other parts to form a microgrid to improve the stability of grid-connected operation.The structure,principle and model of the microgrid and its constituent units are theoretically analyzed at first in the thesis.Secondly,establish a model of the HESS based on the working principle of it,and the power fluctuations in the microgrid is suppressed through the coordinated control of converters.Finally,establish a capacity configuration model of HESS,use the optimization algorithms to solve the example and obtain the optimized configuration of equipment.The thesis mainly carried out the following researches:(1)The DC microgrid with photovoltaic and wind power as the power source is the basic platform for studying HESS.Firstly,construct the power balance equation of the microgrid in different operation modes.Secondly,establish the mathematical model of photovoltaic and wind power generation units,the basic principles and the maximum power tracking method of the two power generation methods are analyzed.And finally,introduce the DC bus voltage into the control of the grid-connected converter to realize the regulation of the bus voltage by the power grid.(2)Taking factors such as technical performance and economic cost into consideration,lithium battery and super-capacitor are selected as the main components and active topology structure is used to form the HESS.Power coordination and charge-discharge control of energy storage devices are realized through power distribution and converter control.Propose an improved charge and discharge protection of energy storage equipment to reduce the output power fluctuations caused by the switching of the working state when the equipment is overcharged or overdischarged.The effectiveness of the improved control method is verified by simulation operation.(3)Establish a HESS capacity configuration model based on cost calculations.The annual investment cost,operation and maintenance cost,and power fluctuation penalty cost of energy storage equipment are used to construct the objective function.The constraints of microgrid and energy storage equipment are considered at the same time.Particle Swarm Optimization algorithm is used for optimization calculation,and finally,the HESS configuration is compared with the configuration of single energy storage system which optimized under the same example,and it is verified that the HESS have better economic efficiency.(4)Establish a microgrid simulation model based on the theoretical analysis of the component units and the HESS.Simulation experiments under different working conditions are designed in the off-grid and grid-connected mode,and the results show that the coordinated control of HESS can effectively suppress the renewable energy power and load power fluctuation,maintain the stability of grid-connected power and bus voltage. |
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