Research on Cooperative Fault Ride-through Strategy of Offshore Wind Power Grid-Connected System via VSC-HVDC System

Abstract

Aiming at the problems of weak fault ride-through capacity of offshore wind power grid-connected system, heating of DC energy consuming devices and waste of electric energy, etc. In this paper, a cooperative fault ride-through strategy combining blade energy storage and DC energy dissipation device is proposed. On the basis of analyzing the overvoltage mechanism of DC side and the control principle of flexible converter station during fault, a fault ride-through method based on blade energy storage is proposed, which is simulated and verified on Matlab/Simulink simulation platform. According to the high-voltage and low-voltage fault ride-through standard of wind turbines in China, the expression of the reference value of active and reactive current of flexible converter station in fault ride-through period is determined. Combined with the fault degree and the margin limitation of energy storage by blade kinetic energy, the switching strategy of DC energy dissipation device is designed., and then the overall control strategy of wind farm blade energy storage and DC energy-consuming devices is put forward. Finally, the experimental tests are carried out on the hardware-in-the-loop simulation platform at the controller level. The simulation results under different working conditions show that the control method proposed in this paper can not only realize the fault ride-through of Offshore wind power grid-connected system through Voltage Source Converter-High Voltage Direct Current (VSC-HVDC), but also effectively solve the waste of electric energy and the heating problem of DC energy-consuming devices, and prolong its service life.