摘要：The modern grid rules forces DFIG to withstand and operate during single as well as multiple low
voltage grid faults. The system must not lose synchronism during any type of fault for a given
time period. This withstanding capacity is called low voltage ride through (LVRT). To improve
performance during LVRT, enhanced field oriented control (EFOC) method is adopted in rotor
side converter. This method helps in improving power transfer capability during steady state and
better dynamic and transient stability during abnormal conditions. In this technique, rotor flux
reference change from synchronous speed to some smaller speed or zero during the fault for
injecting current at the rotor slip frequency. In this process, DC-Offset component of flux is
controlled beyond decomposing to a lower value during faults and maintaining it. This offset
decomposition of flux will be oscillatory in conventional FOC, whereas in EFOC with internal
model controller, flux can damp quickly not only for single fault but during multiple faults. This
strategy can regulate stator and rotor current waveform to sinusoidal without distortion during
and after fault. It has better damped torque oscillations, control in rotor speed and generator flux
during and after fault. The fluctuations in DC bus voltage across capacitor are also controlled
using proposed EFOC technique. The system performance with under-voltage grid fault of 30%
and 60% of the rated voltage occurring at the point of common coupling during 1 to 1.25 and
another fault between 1.6 to 1.85 seconds are analyzed using simulation studies.
关键词：DFIG; Field oriented control; Internal model control; low voltage ride through; recurring faults; recurring;
faults.
