Improvement of fault ride through capability of synchronous generators with excitation boosters

L. Díez Maroto, J. Renedo, L. Rouco, F. Fernández-Bernal

Summary:
Excitation Boosters (EB) are aimed at improving Fault Ride Through (FRT) capability of synchronous generators equipped with bus fed static excitation systems by means of adding a supplementary voltage or current source to the rectifier. Alstom patented a voltage EB, whose main component is an ultracapacitor that is connected to the field winding in case of a fault by an on/off controller. The ultracapacitor is sized in such a way that the FRT capability is improved when the generator is connected to an infinite bus. However, the paper shows that EBs governed by on-off controllers may result in adverse effects in case of remote faults from generators that may occur in multi-machine systems. To sort this problem out, a controller that modulates the EB voltage using the generator speed deviation with respect to the speed of the Center Of Inertia (COI). The speed of the COI is obtained using a Wide Area Measuring System (WAMS).

Keywords: Excitation Booster, Ultracapacitor, Bus Fed Static Excitation System, Fault Ride Through Capability, Grid Codes, Transient Stability, WAMS.

Registration date: 08-jun-2016