Research On Low Voltage Ride Through Technology Of Doubly-Fed Wind Power Generation Based On Rotor Crowbar Circuit

With the rapid development of human society,the demand for clean energy has increased dramatically,and the proportion of wind power generation in the power grid has also increased.If the power grid is severely faulted and the large-scale wind turbines connected to the power grid are decommissioned,it will have an adverse effect on the safe and steady running of the power grid system.Therefore,doubly-fed wind turbines have low-voltage ride-through capability,which has become a necessary condition for grid-connected wind power.When the voltage drops due to a fault,it can continue to operation without going off the network to ride through the fault,and transmit reactive power to the grid to support the grid voltage.This article mainly studies the low voltage ride through technology of the rotor Crowbar circuit.This article first outlines the importance of developing wind power in global energy development and the scale of China's wind power development,and introduces the current research status and problems of low-voltage ride-through control strategies for domestic and foreign double-fed wind turbines.The advantages and disadvantages of the existing schemes based on various low voltage crossing technologies are expounded.The basic component and theory of DFIG-based wind power system are explained.The mathematical model of power converter is established and its control strategy is given.Then,a conventional rotor Crowbar protection circuit uses a fixed resistance resistor,which makes it incapable to suppress the increase of the rotor over current and the rise of DC bus voltage.Doubly-fed induction generator(DFIG)group low-voltage ride-through scheme,established the Crowbar resistance calibration method,combined with the transient process of DFIG during voltage failure,developed a control strategy with adjustable resistance value to achieve the switching control of Crowbar resistance and adjustment resistance.The PSCAD/EMTDC simulation platform is used to set up a dynamic simulation model of DFIG and grid faults.The simulation and traditional Crowbar protection circuit schemes are compared and analyzed.This scheme can effectively suppress the increase of rotor current and DC bus voltage together.Finally,the reactive output characteristics of DFIG are analyzed.In order to solve the problem that the voltage drop is more serious after the unit is put into Crowbar during the fault,the STATCOM is introduced as the wattless power compensator of the DFIG wind turbine.The reactive voltage control strategy of DFIG and STATCOM before and after the Crowbar investment was established,and a set of reactive voltage regulation schemes jointly participated by the doubly-fed induction generator and the reactive compensation device STATCOM was formulated.Simulation consequences indicate that this scheme can efficaciously promote the LVRT capability of DFIG-based wind power system compared with only the DFIG scheme for reactive voltage regulation.Figure[48]table[1]reference[82]...