Research On Active Frequency Modulation And Fault Ride Through Strategy Of Offshore Wind Power

In recent years,under the background of the establishment of the national "dual carbon" target,the construction scale of offshore wind farms has been expanding,and the security and stable operation threats access to the power grid are also increasing.In this paper,the offshore wind power system is selected as the research object,and the active frequency modulation strategy of the offshore wind power unit is studied in view of the transient stability of the active power loop to the power system under grid-connection.In addition,the fault voltage crossing capability of the wind power unit is studied for potential voltage faults in the grid.Among the main wind turbines,the direct-driven permanent magnet synchronous wind generator has higher efficiency and more flexible control mode,which is one of the current research hotspots.The grid-connected inverter mainly adopts virtual synchronous generator algorithm,so that the unit has inertial support capacity.Therefore,for the direct-driven permanent magnet synchronous wind generator combined with the grid-connected virtual synchronous generator technology,the following research work is carried out in this paper:Firstly,the structure and characteristics of the offshore wind power system are analyzed from the perspective of wind turbine characteristics.According to the composition of the offshore wind power system,including the dynamic characteristics of wind,wind turbine with part of mechanical transmission,wind generator and the two-side grid-connected inverters,the mathematical models are derived respectively,and the equivalent modeling method of the wind farm is unified.Secondly,the simulation model establishment is analyzed under the theoretical model of wind turbine,and the 1.5MW offshore full-power permanent magnet direct-driven wind generator model is built based on MATLAB/Simulink.The correctness and practicability of the model are verified by the simulation results.Then,for the grid-connected frequency stability,the maximum power tracking point under load reduction control is proactively adjusted to ensure the balance of power and frequency.For the load power deficiency that cannot be covered by the maximum power,an additional integral regulator is proposed to carry out active secondary frequency modulation to optimize energy distribution.Finally,the additional current instruction is proposed to compensate the input voltage at the VSG to provide reactive power support,and the energy storage device under hysteresis control strategy at the DC side of the converter is proposed to ensure the active power balance.The feasibility and effectiveness of the proposed strategies are verified by the simulation results.