Research On High Voltage Ride-through Control Strategy And Parameter Identification Method For Doubly-fed Wind Turbine

In recent years,China’s wind power grid-connected technology has developed rapidly.Doubly fed induction generator(DFIG)is widely used in onshore distributed wind power generation with the advantages of smaller excitation capacity and independently adjustable active and reactive power.However,the problem of large-scale off-grid due to its weak high-voltage ride-through capability is more prominent.Meanwhile,to ensure the correctness of DFIG gridtie fault ride-through process,reasonable and accurate converter control parameters are especially important.Therefore,it is important to study the control strategy and parameter identification of DFIG high voltage ride-through control.In this article,the DFIG high-voltage ride-through electromagnetic transient model and the control parameter identification are studied,and the problem of overvoltage and reactive power compensation at the bus of a doubly-fed wind turbine with sudden grid voltage rise is briefly analyzed.The main studies are as follows:Most of the research on high-voltage ride through(HVRT)control strategy for doubly-fed asynchronous wind turbines focuses on the rotor-side converter,while the effects of network-side converter current transients on the DC bus voltage and reactive power are often neglected.According to the analysis results,the effect of suppressing DC bus transient overvoltage is limited when the turbine voltage rises suddenly.Therefore,the active and reactive currents of the network-side converter and the limiting factors of the DC bus voltage are first analyzed to reveal the influence of the variation characteristics of the network-side current on the amplitude of the oscillation of the DC bus voltage during the turbine voltage transients.Based on this,a control strategy considering the dynamic changing characteristics of the network-side current is proposed,and the reference values of the network-side active and reactive currents of the wind turbine HVRT are redesigned.Secondly,the key parameters in the proposed control strategy are optimized using the Gray Wolf algorithm to obtain the most suitable DC bus voltage value.However,the current "black-boxing" of converter control parameters seriously affects the analysis and improvement of grid-connected wind turbine technology,and the need for accurate parameter identification needs to be enhanced.In this article,we construct the inner and outer loop transfer functions of the rotor-side and grid-side control systems of doubly-fed wind turbines as the parameter identification model and propose the excitation method of applying different disturbance sources to the inner and outer loops and the step-by-step parameter identification method using optimization algorithm.In particular,reasonable observation quantities are selected to avoid the cascade problem between the inner and outer loops.Finally,the doubly-fed wind turbine high voltage ride-through control model established in the previous section is tested.The external characteristic parameters are important indicators reflecting the grid-connected characteristics of wind turbines.In this study,a least-squares parameter fitting method is used and a weighted error analysis method is proposed,which is finally tested for the DFIG highvoltage ride-through model data as well as the XX manufacturer output data.