Abstract:A simple tracking algorithm for single-phase reactive current detection was proposed aimed at the single-phase client SVG with the direct-current-control-strategy. Within one caculation period,the algorithm used the phase-locked loop (PLL) circuit to gain the product of load current and standard sine wave which was of the same frequency and voltage with the supply voltage but lagged behind 1/4 cycle. The product results were stored into a storage queue of sampling data. The reactive current was fast trackled by comparing the sampled data pre and post the cycle of fundamental wave in the queue. The results of analysis show that the reactive cunent can be accurately extracted in one cycle and the tracking effect of the cun'ent change is good and the anti-interference capability is obvious. The algorithm is simple and fast, and needs only 2 multipliers, so it can be easily realized.