The power plant auxiliary drive system will work abnormally or even trip due to frequency converter voltage drops, which might be caused by transient state process of auxiliary power system or the external grid. Low voltage ride through (LVRT) is an effective way to solve the above problem. Based on the actual status of power plants, installing attachment devices, which can achieve LVRT, becomes a mainstream solution. Because it does not require a lot of changes to the original circuit. Voltage boost module between AC and DC side, energy storing device on DC side and on-line UPS on AC side are typical methods for attachment devices. Modeling and simulation results show that the first method will cause DC side overvoltage, but this method is less costly. The second and third methods have better LVRT support capability, but these two methods are more expensive. Which method should be adopted according to the analysis of economy efficiency and on-site condition.

Attached Equipment,Low voltage ride through,Additional booster modules,Energy storage equipment,On-line UPS