Parameter Identification And Optimization Control Of Microgrid System

The development of electric energy has a driving effect on social development.New energy power generation such as photovoltaic power generation and wind power generation is an inevitable trend of social development.However,due to the volatility and randomness of new energy power generation,it often causes unstable voltage and frequency,which is easy to cause great impact on the large power grid,so the microgrid technology emerges as the times require.With the wide application of microgrid technology,higher requirements are put forward for its security,stability and reliability.In this paper,two aspects of microgrid system inverter parameter identification and parameter optimization of secondary frequency modulation controller are studied.The main contents of the research are as follows:(1)This dissertation summarizes the generation,definition,development and characteristics of the microgrid system,and lists typical microgrid demonstration projects and projects in various countries.The research status of microgrid inverter parameter identification and secondary frequency modulation control is summarized.(2)It briefly summarizes the three kinds of microgrid inverter control strategies of PQ,VF and Droop.The VSG control strategy and its specific control structure are emphatically introduced,and its second-order linear model are established,which provides a basis for the parameter identification of VSG.At the same time,the influence of inertia and damping on the output power of the inverter is analyzed.Finally,the correctness of the VSG control strategy and theoretical analysis is verified by simulation and experiment.(3)The identification of inverter parameters in microgrid system is studied.According to the transfer function model of VSG output to input power and the relationship between model parameters and VSG inertial time constant,an identification strategy for identifying the inertial time constant of VSG is proposed,which performs the auxiliary variable method after equivalent filtering of input and output data.Finally,the correctness of the theoretical analysis and the effectiveness of the proposed strategy are verified by the simulations and experiments.(4)Firstly,the principle of secondary frequency modulation control in micro grid system is briefly analyzed,and the strategy based on PI control of secondary frequency modulation control in microgrid system is introduced.Then,the paper proposes a control strategy of the secondary frequency based on the linear quadratic optimal control.Meanwhile,the parameters of the frequency control controller are designed.Next,the small signal model including secondary frequency modulation is built,and the influence of the controller parameters on the system stability is analyzed.Finally,the feasibility and effectiveness of the proposed control strategy are verified by simulation.