A new detection method based on synchronous reference frame is proposed. A single-phase voltage is derived and used to form virtual symmetrical three-phase system. Sine signal and cosine signal are formed in this reference frame. It substitutes the low pass filter by simple integral, delay and gain, which can reduce the detecting delay to 1/6 of source period. The compensation current is derived, which is more accurate than in unbalance voltage conditions. This method needs simple calculation without the phase-locked-loop and can meet load compensation demand of DSTATCOM under asymmetrical voltage conditions. The real-time and effectiveness of the detection method as well as better compensation of compensation currents are verified by simulation results.