A dynamic strategy to improve the ride-through capability of a fixed speed induction generator

Based on the analysis of the short current of the fixed speed induction generator (FSIG) under symmetrical system faults, a strategy using the dynamic voltage restorer (DVR) is proposed to improve the low-voltage ride through (LVRT) capability of FSIGs. During the system fault, LVRT-DVR is connected in series between the grid and the generator by switching-off the by-pass bidirectional thyristors and provides a compensating voltage to isolate FSIG from the system fault. To increase the switch-in speed of LVRT-DVR, an antivoltage technique is used to shut the thyristors off immediately. After the fault is cleared, the phase-shifting control is applied to avoid phase jumps of the FSIG terminal voltage. The PSCAD/EMTDC simulation and field tests have been carried out to prove the effectiveness of the proposed LVRT strategy, and related conclusions and comments are summarized.