College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China

Since industrial installations are much more sensitive to voltage drops than frequency deviations, it is essential to guarantee the stability of voltage during severe faults. First, the main factor that affects the AC voltage in the passive system is analyzed. According to the analytical results, the control strategy is proposed to increase the AC voltage in transient conditions. The strategy consists of two parts, i. e. , a modified current limit tactic and a frequency hysteresis control. The simulation tests uring metallic single-phase and three-phase faults are done via PSCAD/EMTDC to verify the validity of the control methods.