Research On Fault Ride Through Control Strategy Of Doubly Fed Wind Power Generation System Based On Series Compensator

With the maturation and improvement of wind power technologies in various countries in the world,the proportion of wind power generation in the global power industry has grown rapidly.Double-fed induction generator has many advantages,such as small capacity,light weight,and high control flexibility.It is widely used in high-power wind power generation sites above megawatts.However,because the stator of the doubly-fed wind power generator is directly connected with the power grid,it is greatly affected by the power grid fault.Therefore,it has certain practical significance and value to study the fault traversing technology of the doubly-fed wind power generation system.This paper proposes that the series compensator with three-phase four-leg structure is applied to the doubly-fed wind power generation system,which can improve the stability of the doubly-fed generator system under steady and unbalanced grid voltage and enhance its transient voltage drop in the grid.Low-voltage ride-through capability under fault.Firstly,the topology of the doubly-fed wind power generation system based on the series compensator is given and the mathematical model of the entire system is established.The basic control strategies of the grid-side converter and rotor-side converter of the doubly-fed wind power generation system are introduced.The three-phase four-leg topology used in the series compensator is analyzed in detail and the corresponding control strategy is given.The influence of unbalanced grid voltage on the normal operation of the motor body and grid-side converter in the doubly-fed wind turbine generator set is analyzed in detail through formula derivation and equivalent circuit.On this basis,the control strategy of the doubly-fed wind power generation system based on the series compensator under unbalanced grid voltage is proposed.The output of the appropriate compensation voltage through the series compensator eliminates the negative-sequence component of the stator-side voltage of the doubly-fed generator and improves The status of the grid-side converters.Thus,the stability of the operation of the entire doubly-fed wind power generation system under unbalanced grid voltage conditions is greatly improved.The transient characteristics of doubly-fed generator are analyzed when the voltage of the pcower grid drops instantaneously,and the mechanism of rotor over-current generation is described.From the perspective of mitigation of stator voltage abrupt changes,a slash voltage compensation strategy based on a series compensator doubly-fed wind power generation system is proposed,which can suppress the sudden rise of the stator and rotor currents of the doubly-fed wind power generation system during the drop and recovery of the grid voltage.The traversing operation of the feed-wind power generation system under the short-circuit fault of the power grid enhances the ability of the double-fed wind power generation system to pass through the low voltage.Through simulation analysis and experiments,the correctness and effectiveness of the control strategy of the double-fed wind power generation system based on the series compensator under the two fault conditions of grid voltage unsteady state and transient voltage drop of the power grid are verified.