Mitigating the impact of voltage sags and swells on type IV wind generator systems

This paper proposes a unique coordinated ride-through capability enhancement scheme for Type IV wind generators to counter the impact of symmetrical and asymmetrical voltage swells. A novel protection hardware configuration is utilized to restrict the dc-link overvoltage and undervoltage in the event of voltage swells at the Point of Common Coupling (PCC), which would otherwise damage the converter. Moreover, a reactive power flow management algorithm is implemented to support the grid voltage during the transient event. A supervisory controller is used to control the insertion of the protection hardware and also to regulate the reactive power flow between the generator and grid. It is observed that there is substantial improvement in ride-through performance. A 10-MW Wound Rotor Synchrnous Generator (WRSG) wind farm in MATLAB/Simscape Power Systems is utilized to validate the effectiveness of the scheme. The 10 MW wind farm consists of 5 × 2-MW wind generators.