Research On Control Strategy Of Large-scale Photovoltaic Power Station Connected To AC System Via VSC-HVDC

As a kind of clean and renewable energy,new energy is not harmful to the global development.As a kind of green and renewable energy,solar energy is one of the energy sources that human beings rely on for sustainable development.In the past decades,solar photovoltaic power generation has changed from the original "roof plan" to "roof plan" With the development of large-scale photovoltaic into the power grid step by step,with the strong support of our government,photovoltaic power generation is a direction of power development in the future.Most of China’s solar energy resources are distributed in the western region,and the power transmission of the power generation base in the western region hasbecome a hot issue in the development of new energy.In order to achieve the goal of large-scale photovoltaic into the grid,this paper studies the photovoltaic power transmission.Flexible DC transmission can solve large capacity photovoltaic long-distance transmission,because the photovoltaic power station has the ability of bottom voltage ride through.When the AC power grid fails,it can have a little stability function for the system.This paper studies the flexible DC transmission,analyzes the control strategy and operation mode,and models and simulates the large-scale photovoltaic grid connection and the voltage sag after grid connection,so as to ensure the stability of the system In case of power grid failure,it can quickly solve the active and reactive power balance of VSC-HVDC System,stabilize DC voltage and improve system reliability.In view of the above problems,this paper proposes the virtual synchronous machine(VSG)technology for large-scale photovoltaic to enter the AC power grid through VSC-HVDC.In terms of VSG technology and low voltage ride through technology,the control method of photovoltaic through converter station is improved.When the power grid fails,the stability of the power grid can be improved by mode switching.This paper discusses the requirements of low voltage ride through for largescale photovoltaic grid connection The VSG control technology is applied to the converter,and the simulation model is built to verify the practicability and frequency of the converter with Matlab / Simulink.The grid connection of photovoltaic power station via VSC-HVDC has become an irresistible trend.This paper studies the whole start-up process of large-scale photovoltaic grid connection,which slows down the impact of large voltage fluctuation on the power grid during grid connection start-up,and realizes non impact start-up.For the possible faults of the system after grid connection,a control strategy based on VSG large-scale photovoltaic grid connection via flexible DC is proposed,which is symmetrical to the power grid The simulation results show that the fault ride through can be tested when the voltage sag occurs in AC power grid.