Research On Control Measures Of Low Voltage Fault Ride Through In Double-Fed Wind Farm

With the progress of science and technology and industrial level,vigorously developing and utilizing clean energy such as wind power and renewable energy is the most effective way to solve the problem of non-renewable conventional energy.In order to meet the requirements of doubly-fed wind turbines,they will not fall off from the power system when voltage sag occurs within a certain range due to grid faults.To solve this problem,this paper analyzes the structure of the doubly-fed induction generator and the transient mathematical model when the power grid voltage sags,and proposes to apply the Crowbar protection circuit and(Static Synchronous Compensator,STATCOM)to improve the low-voltage compensation ability of the doubly-fed wind farm.The research focus of this paper is as follows:With the increasing proportion of wind power generation devices in the power grid,the time-varying of wind power resources and the voltage sag of power system faults will have an impact on the wind power generation system,making the rotor side overcurrent,which will cause large-scale wind power devices to be detached from the grid in serious cases.In order to solve the problem of stator flux oscillation and DC or negative sequence component of doubly fed induction generator caused by serious voltage drop in power system faults,the rotor side converter overcurrent is induced by high-speed rotating rotor side,which will damage power electronic devices in serious cases.Therefore,it is necessary to install low-voltage Fault-Crossing control measures for doubly-fed wind farms.When the fault voltage of power system falls seriously,the active bridge Crowbar protection circuit is used to unload the excess energy of power grid to help the system realize LVRT.Since Crowbar protection circuit will be put into the system and connected to the rotor side converter at the same time to suppress the overcurrent,the system works in the state of traditional induction motor,which needs to absorb a lot of reactive power from the grid,and the system lines and transformers also need a lot of reactive power support.Therefore,the control measures designed in this paper are to realize LVRT by using STATCOM and Crowbar protection circuit.A simulation experiment platform is built on MATLAB/Simulink platform to simulate the LVRT capability of the system under different control measures.Part of the experimental platform of STATCOM was built based on TMS320F28335 chip.The experimental test system was based on the NI instrument PXI hardware detection system.The test system software was based on LabVIEW programming language to realize the display part.The hardware and software components are designed to further validate the accuracy of the design.