Research On Virtual Inertia Grid-Connection Control Of Doubly-Fed Wind Turbine System Based On Voltage Orientation

With the excessive use of fossil fuels,pollution and lack of energy problem has gradually attracted national attention,and the development of new energy sources is becoming the focus of energy research.Wind energy has attracted special attention among all kinds of new energy because of its advantages such as abundant energy and no pollution.In recent years,as the proportion of wind power generation in the power system gradually increases,its impact on the performance of the power system after being connected to the grid is gradually deepened.As the new energy grid-connected converters are mainly power electronic devices,for example,wind power grid-connected converter,the power system lacks the inertial response characteristics necessary to maintain system stability.This paper analyzes the low inertia problem of wind power generation,and introduces the current control strategy of wind power generation system to improve the inertia response,and then carries out the research on the optimization of wind power inertia.Firstly,the system structure of the doubly-fed wind turbine is briefly introduced,the models of the back-to-back sides converters in different coordinate systems are established,and the related control strategies are analyzed.Focusing on the control strategy of the rotor side converter,the problems of grid-connection accuracy in the traditional stator flux directional control are analyzed.Aiming at the above problems,the stator voltage-oriented control strategy is adopted and its mathematical model is studied in depth.The feasibility of this strategy is verified by the relevant simulation model built on MATLAB /Simulink platform.Secondly,the principle and structure of virtual inertia control strategy are analyzed in detail by studying the working characteristics of synchronous generator.Then,the virtual inertial grid-connected control small signal model is deeply analyzed,and the important parameters of the control strategy are selected and designed from the aspects of steady state performance and transient performance.In addition,a pre-synchronization strategy without phase-locked loop(PLL)is adopted to improve the pre-synchronization process of the independent strip loading into the grid-connection process.The effect of parameter change on system performance and the validity of pre-synchronization control are verified by simulation.Finally,experimental verification is carried out on the d SPACE experimental platform,which realizes the process from independent loading to grid-connected operation control under the virtual inertia control strategy,and verifies the effectiveness and correctness of the proposed scheme.