| A lot of electrical energy is consumed in the production process of high energy-consuming light chemical companies such as paper making,ceramics,this will cause a series of environmental pollution problems.Photovoltaic power generation is an effective supplement to traditional power due to some advantages such as no pollution,flexible installation and no geographical restrictions.This power generation is often combined with factories or industrial parks to form a regional microgrid that provides an effective way for the use of new energy power in light chemical companies.When the regional photovoltaic energy storage DC microgrid is used,the rational configuration of photovoltaic,energy storage capacity and the design of an effective coordinated control strategy are some crucial factors to ensure the economic,stable and efficient operation of the hybrid energy storage microgrid.This thesis focuses on the improvement of mathematical models suitable to photovoltaic energy storage microgrid,the storage capacity configuration of integrated photovoltaic energy,the configuration capacity optimization of hybrid energy storage,coordinated control strategies and the stability improvement of systems.The main contributions are given as follows:(1)The improvement of photovoltaic models using geographic location information and the improvement of battery model considering lifetime attenuation factors.Based on the traditional photovoltaic model,we establish a photovoltaic optimization model by combining the solar altitude angle and the photovoltaic cell temperature.The model through the geographic latitude correction of photovoltaic output power,obtain the photovoltaic output power value closer to the actual geographical environment.For the storage battery life model considering the charge and discharge ratio,the charging and discharging ratio of energy storage in the microgrid is affected by the system operation,generally uncontrollable variables,the life model is unsuitable for the microgrid study.In this thesis,the effect of charge and discharge ratio on energy storage is equivalent to the energy storage state of charge(SOC)and discharge depth(DOD),the life decay model is optimized for the combined effect of calendar decay and cyclic decay,it is more suitable for the needs of photovoltaic storage microgrid capacity allocation and coordinated control.(2)Photovoltaic energy storage capacity configuration of photovoltaic energy storage integration.Aiming at the independent configuration of traditional photovoltaic and energy storage,there is a problem of poor matching of source,storage and load,which affects the reliability and economics of the system.Based on the known load curve,taking photovoltaic and energy storage as a whole,establish an integrated photovoltaic-storage configuration model with load shortage rate and energy overflow ratio as comprehensive targets,and the cost model of the entire life cycle of energy storage during the project cycle.Comprehensive allocation model and cost model,calculate the optimal allocation of photovoltaic and common energy storage battery capacity without considering the time-of-day electricity price of the power grid and the time-of-day electricity grid.The results prove that the integrated configuration can obtain the optimal allocation capacity of photovoltaic and energy storage while meeting the load energy demand.(3)Capacity optimization of hybrid energy storage configuration based on improved crow search algorithm.Aiming at the result of the integrated photovoltaic energy storage capacity allocation,in order to extend the service life of the energy storage system and ensure the stability of the microgrid operation,it is necessary to find the best ratio of energy density and power density batteries in the total energy storage capacity.In order to improve the traditional multi-objective optimization algorithm with many iterations and low accuracy,this thesis proposed an improved crow search algorithm that combines the idea of sharing the optimal position in the particle swarm and the idea of Levi's flight.The analysis results of examples show that:compared with the traditional particle swarm algorithm and crow search algorithm,the improved algorithm has the advantages of fast convergence speed and more accurate results.Within the effective range of load shortage rate and energy overflow ratio,power batteries and energy batteries can be obtained the best capacity ratio.(4)Study on multi-mode coordinated control and adaptive power allocation strategy for photovoltaic storage microgrid.Based on the configuration of photovoltaic energy storage capacity,aiming at the more complicated problem of centralized or hierarchical coordinated control in microgrids.Design DC bus voltage grading coordinated control strategy with droop control as the core.The simulation analysis of seven designed scenarios proves that the strategy can maintain the bus voltage in the range of 380V?420V.In addition,aiming at the problem that hybrid energy storage cannot fully exert the working characteristics of different types of energy storage in coordinated control,in the hybrid energy storage control link,a frequency divider is designed to divide the net power in the microgrid.The high-frequency power is suppressed by the power battery,and the low-frequency power is suppressed by the energy battery.In order to make the energy battery and the power battery have the same charge capacity,an adaptive frequency divider is designed in the hybrid energy storage control link,which can automatically adjust the frequency bandwidth according to the net power of the system and the state of charge of the hybrid energy storage.Simulation results verify that the proposed frequency division control can effectively prolong the service life of energy-type batteries and improve the state of charge balance of hybrid energy storage batteries.(5)The self-stability improving strategies of microgrids based on virtual motors.For the power electronic converter has the characteristics of weak damping and low inertia of the DC microgrid,which causes the DC bus voltage transient stability deteriorates and then affect the grid-connected power quality.Based on the coordinated control of hybrid energy storage,the thesis designs the virtual motor control strategy.Design dual PI+virtual DC generator control strategy for power battery energy storage converters,and design a virtual synchronous machine control strategy for grid-connected inverters.Through the combination of two virtual motor control strategies,the microgrid DC bus voltage fluctuation is limited Within ±2.5%UDC,the total harmonic distortion of grid-connected AC power is maintained within 3%,and the system's self-stabilizing ability is effectively improved. |
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