| In recent years,fossil energy shortages and environmental pollution problems have become increasingly prominent,and the development of renewable energy is considered to be one of the important ways to deal with such problems.The microgrid is an important form of integrated distributed renewable energy generation.It has a flexible operation control mode to achieve a high proportion of distributed renewable energy.With the large-scale emergence of DC power equipment such as photovoltaic,energy storage battery,electric vehicle and DC electrical appliances,the formation of DC micro-grid can reduce the energy conversion process and improve the conversion efficiency,without considering the frequency,phase and other issues,and the control method is simpler.At the same time,the application of microgrid technology has also transformed users from the original “electricity consumers” into “electricity prosumers” with multi-roles of generating,storing,selling and using electricity,and under the support and guidance of relevant policies,through appropriate trading mechanisms and ways,the electricity transactions between users can be carried out.In order to promote the near and in-situ absorption of renewable energy and improve the generation income of microgrid users.In view of the above,this thesis focuses on the operation control strategy of DC microgrid with photovoltaic and storage system for peer-to-peer electricity trading,and formulates the control strategy of DC microgrid with photovoltaic and storage in normal operation mode and electricity trading mode.The main work of this thesis includes:Firstly,the important components of the DC microgrid are modeled and analyzed.The output characteristics of photovoltaic cells are studied,the corresponding relationship between photovoltaic cells and environmental temperature and light intensity is analyzed,and the maximum power tracking control algorithm of photovoltaic cells is summarized;the role of energy storage battery in microgrid and its mathematical model are analyzed,and the charging and discharging control strategy of energy storage battery is proposed;the mathematical model of bidirectional DC/AC converter in microgrid is analyzed.The control of DC/AC converter based on SVPWM algorithm is simulated and analyzed by using MATLAB/Simulink software.Secondly,the equivalent circuit model of DC microgrid is analyzed,and two regulation strategies of DC microgrid under centralized communication control and distributed control are proposed.Considering the two operation modes of microgrid,switching regulator according to different operation states under centralized communication control and coordinating the operation mode of converter in microgrid according to DC bus voltage signal under distributed control,the two control modes are verified at last.Finally,a control strategy for peer-to-peer electricity trading between DC microgrid users based on bus voltage stratification is proposed for DC microgrid.The strategy divides the DC bus voltage hierarchically,sets the converter action threshold of converter,the mode switching point,the electricity trading mode operating point,the external triggering condition of the electricity trading,and the internal execution conditions,and realizes the electric energy through coordinated actions between the units within the microgrid.The smooth realization of the trading process and the effective execution of trading actions. |
