Aimed at the problems of active power fluctuation and current asymmetry of a Vienna rectifier caused by asymmetric grid, active power fluctuation suppression control (APFSC) and symmetric positive-sequence current control (SPSCC) are introduced. Due to the current limitation of power devices, the use of APFSC will reduce the maximum active power of the Vienna rectifier. In comparison, the use of SPSCC can expand its maximum active power at the cost of significant active power fluctuation. With the comprehensive consideration of disadvantages of the above two methods, an improved power control (IPC) strategy is proposed. When the processing power of the Vienna rectifier is small, keeping the active power without fluctuation is the primary control target. In this case, the effects of IPC and APFSC are the same. The active power fluctuation under IPC is effectively suppressed, while that under SPSCC is large. When the processing power of the Vienna rectifier is large, meeting the power demand is the primary control target, but the active power fluctuation should be reduced as much as possible. Under this circumstance, IPC can meet the active power demand, but APFSC cannot meet the power demand. On the premise of meeting the power demand, the fluctuation of active power under IPC is smaller than that under SPSCC. Finally, experimental results verified the advantage of the proposed control method.