Research On Control Strategy Of Virtual Synchronous Generator Based On Micro Grid Inverter

Energy crisis and environmental pollution promote the development of renewable energy,such as wind energy and solar energy.Distributed generation technology and micro grid technology get more and more attention.As the access form of distributed power,micro grid inverter plays an important role in improving the permeability of distributed power and enhancing the stability of electric power system.In order to make the power electronic interface grid connected inverter have this excellent characteristic,the virtual synchronous generator technology which simulates it as synchronous generator came into being.It can not only improve the compatibility and stability of power grid,but also reduce the influence of large-scale inverter access on the operation mode of power system.Therefore,it is of great significance to study the micro grid inverter based on virtual synchronous generator technology.Firstly,this paper introduces the concept and research status of micro grid,the concept and research status of virtual synchronous generator technology.This paper describes and analyzes the PQ control,V/f control and droop control,which are the common control strategies of the traditional micro grid inverter,and builds the corresponding simulation model.According to the simulation waveform analysis and comparison of the relevant operation characteristics,advantages and disadvantages and application occasions,the virtual synchronous generator technology is introduced.Secondly,referring to the mathematical model of the synchronous generator,comparing the main circuit topology of the virtual synchronous generator,the control principle of the virtual synchronous generator is introduced in detail,and the governor and excitation regulator are designed.The three closed-loop control method of virtual synchronous generator is realized by cascading double closed-loop voltage and current inner loop control mode to virtual synchronous generator controller.The power regulation principle of VSG under grid connected and off grid is described respectively.The validity of using VSG to control the operation of micro grid inverter is verified by building simulation model and experiment.Thirdly,in order to improve the performance of the control system of VSG,small signal modeling is carried out for the process of VSG passively adjusting the output power in response to superior command and actively adjusting the output power in response to the state change of power grid,the main parameters are analyzed,a complete set of parameter design method is proposed,and the selection of parameters is optimized through the control variable method It is concluded that the range of parameters should be different in different states.The correctness and effectiveness of the control scheme are verified by the simulation model and experimental comparison.Finally,in order to solve the problem of large frequency fluctuation and offset caused by external disturbance under the control of virtual synchronous generator,a control strategy of virtual synchronous generator based on linear quadratic optimal regulator is proposed.Based on the analysis of the dynamic response of the output frequency and the principle of linear quadratic form,a state equation is established with the angular frequency offset and the power angle offset as the state vector and the input active power deviation as the control vector.The optimal control law of the system is solved,and the stability of the system is analyzed by the second method of Lyapunov.The correctness and effectiveness of the control scheme are verified by the simulation model and experimental comparison.Figure[78]table[7]reference[56]...