Research On Low Voltage Ride Through Technology Based On Stator Side Serides Dynamic Reactance And Virtual Resistance Control Strategy

With the rapid development of China’s wind power industry,the proportion of wind power generation in the power grid continues to increase.When the fault voltage of the power grid drops,it is extremely easy to cause large-scale off-grid operation of wind turbines in the wind farm,which in turn is safe for the grid system.Operation has an impact.Therefore,in-depth analysis of the transient characteristics of wind turbines and the study of low-voltage ride-through technology of wind turbines have important theoretical significance and practical engineering application value for improving the wind turbine’s grid-connected operation capability.First,the structure and basic working principle of the wind power generation system are introduced.By establishing the mathematical model of the doubly-fed wind turbine,the transient characteristics of the doubly-fed wind turbine when the grid voltage drops are analyzed,and the rotor flow of the doubly-fed wind turbine The mechanism of the current phenomenon.Then analyze the advantages and disadvantages of the existing low-voltage ride-through stator series reactance(SSL).For the low-voltage ride-through scheme,the doubly-fed wind turbine system has a long transient transition time,insufficient reactive power output capability,and is easily caused after the reactance is cut off.For rotor overcurrent and other issues,a low-voltageride-through technology for double-fed wind turbines with stator series dynamic reactance(SSDL)combined with rotor side using virtual resistance(VR)flux linkage attenuation control strategy is proposed.Based on this technology,when a fault occurs,the SSDL circuit is put in the stator side.The series reactance value at the initial stage of the fault is determined according to the real-time parameters of the power grid.At the safety threshold,switch to small reactance to improve the reactive power output capability of the doubly-fed fan.In addition,in order to overcome the shortcoming of the transient flux linkage decay time after the stator side series reactance,the virtual resistance flux linkage decay control strategy is introduced on the rotor side,which effectively shortens the transient transition time and further improves the doubly-fed fan.Low voltage ride through performance.Finally,in order to verify the effectiveness of the low-voltage ride-through technology mentioned in the thesis,a simulation system of parallel operation of the doubly-fed wind generator and the infinite grid was built using the simulation software PSCAD / EMTDC.Relevant simulation experiments were carried out.The simulation results show that the proposed ride-through technology scheme can effectively suppress the rotor fault overcurrent and improve the reactive power output capability of the doubly-fed fan during the grid fault.