Research On Grid-connected Control Of Photovoltaic Power Generation System Based On Virtual Synchronous Generator

The traditional PV grid-connected control method is to realize the regulation of the microgrid's output to connect the power grid by simulating the performance of synchronous generator voltage regulation and frequency modulation,but the inertia effect of synchronous generators is not introduced.In addition,the fast response speed of power electronic devices and the problems of harmonic pollution and relay protection caused by frequent interruptions still restrict the further expansion of installed capacity of photovoltaic system.This article focuses on the control technology of virtual synchronous generator(VSG)during the process of the photovoltaic grid-connected,and combining numerical simulation with platform experiment,the main research work is as follows:First of all,it introduces the background of photovoltaic power generation industry and the significance of grid-connected control technology,and analyses of the current research condition of virtual synchronous generator.Building the model of photovoltaic cell unit and inverter output waveform control method in PV grid-connected control technology.The experimental results show that the output power of PV cells is affected by the illumination intensity,temperature and other external meteorological conditions deeply.And the maximum power point tracking(MPPT)method based on observation disturbance method can make PV cells maintain maximum power output in the current environment;the output of voltage waveform in PV cells is regulated by voltage vector control strategy can realize separate control of active power and reactive power,which can better meet the system requirements.The existence of energy storage units in photovoltaic grid-connected systems can enhance the stability of the system.Comparative analysis of three kinds of traditional grid control technology and research on photovoltaic grid connected system using droop control technology.The experimental results show that the PV system can realize the droop regulation of power frequency under the condition of external load fluctuation.However,the response speed of the frequency change is fast,which causes the security hidden trouble to the stable operation of power network..The energy storage units and photovoltaic cells in microgrid are equivalent to synchronous generators in power system and the energy storage unit can emulate the function of speed regulation system in synchronous generator.To establish a photovoltaic energy-storage hybrid grid-connected power system model using VSG control and research.The analysis results show that when the virtual synchronous generator and the grid jointly supply power to the load,the internal energy storage unit of the VSG releases and stores the electric energy according to the fluctuation of the photovoltaic output,and plays the role of regulation of the prime mover;VSG and power grid assume the corresponding active power regulation according to their capacity,and maintain the power balance inside the system under the condition of fluctuating load power.Building a new energy experiment platform,including photovoltaic power generation system,wind power generation system,energy storage battery system and energy management,which the operation of grid connected and off network mode can be realized,and provides a basic experimental platform for the research of distributed energy generation and grid connected control technology.