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Research On Power Fluctuation Control Strategy Of Hybrid Energy Storage System In Photovoltaic Micro Grid

Posted on:2021-01-19Degree:MasterType:Thesis
Country:ChinaCandidate:Z H ChengFull Text:PDF
GTID:2392330629986050Subject:Power electronics and electric drive
Abstract/Summary:PDF Full Text Request
Micro-grid,which uses new energy such as photovoltaic power generation as power supply source,can be applied to power supply in special areas such as islands and remote villages.When the micro-grid with renewable energy operates in isolated island,the output power of its power generation unit is intermittent and random,and the load is also uncertain.The imbalance between the power generation and the load demand power will cause the power fluctuation of the system and affect the stability of power supply.In order to suppress the power fluctuation,the hybrid energy storage device composed of battery and super capacitor is connected to the micro-grid.In view of the low accuracy of power distribution in traditional hybrid energy storage system for suppressing power fluctuation in micro-grid and the problem of delay in traditional PI control hybrid energy storage system,this paper proposes a VMD decomposition power method considering SOC of energy storage medium and an energy shaping control strategy for controlling the output of energy storage medium,which not only solves the problem of over charging and over discharging of energy stora ge system caused by low accuracy of power distribution,and improve the response speed of the system,extend the battery life,improve the stability of the system,the main contents are as follows:Firstly,taking the photovoltaic micro-grid with hybrid energy storage system as the research object,the characteristics of photovoltaic power generation,the charging and discharging model of energy storage medium,the way of hybrid energy storage system connecting to the micro-grid and the hierarchical contro l strategy of micro-grid are analyzed.The coordination control of each unit of micro-grid with hybrid energy storage system is divided into system level control and equipment level control;Secondly,in the system level control,in view of the distributio n of power shortage caused by power fluctuation between the battery and super capacitor,this paper uses VMD decomposition to obtain the power output of different energy storage media,and based on the constraints of the SOC of energy storage media,further modifies the power obtained after distribution,optimizes the VMD decomposition,improves the distribution accuracy,and prevents the super capacitor from over charging and over discharging,Ensure that the super capacitor can be in working state for a long time,so as to reduce the output times of the battery.The method is validated in Matlab/Simulink.The results show that the method can effectively reduce the charge and discharge times of the battery,ensure that the supercapacitor can not be charged or discharged,and improve the utilization ratio of the supercapacitor;Then,in the equipment level control,the main task is to receive the power distribution command at the system level,realize the control of the energy storage converter by modulating the duty cycle of PWM wave,so as to control the output of the energy storage medium of the hybrid energy storage system,and control its charge and discharge,so as to achieve the purpose of stabilizing the power rate fluctuation,in this paper,the passivity of hybrid energy storage system is analyzed firstly.Based on the passivity,a PCH model is established.The method is validated in Matlab/Simulink.The results show that the method can quickly respond to the power fluctuation in the system,effectively reduce the time of bus voltage recovery and improve the stability of micro-grid.Finally,the hardware circuit and software control flow of the system are designed and implemented,and the feasibility and effectiveness of the proposed control strategy are verified by the experimental platform.The experimental results show that,compared with the traditional control strategy,the hybrid energy storage control strategy proposed in this paper can not only effectively smooth the charging and discharging process of the battery,improve the utilization ratio of the supercapacitor,but also quickly stabilize the bus voltage and improve the system stability.
Keywords/Search Tags:Hybrid Energy Storage, Variational Mode Decomposition, Energy Shaping Control, Microgrid
PDF Full Text Request
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