As to grid-connected power quality improvement equipment

such as active power filter（APF）

in order to deal with power quality detection and control

it is necessary to pick up the three-phase fundamental voltage positive & negative sequence component accurately and rapidly.When voltage asymmetry and distortion arising in a.c.network

the ability obtaining the fundamental voltage frequency and phase information quickly and accurately will great affect the power quality improvement equipment performance.In this paper

the fundamental voltage positive& negative sequence component are picked up by according to the theory of synchronous rotating reference frame transformation

using dual-dq transform method

and through the low pass filter（LPF） processing.The phase locked loop function is realized by using negative feedback control theory.Based on the method mentioned above

the fundamental voltage positive & negativee sequence component picking up and Phase Locked Loop function are realized by using FPGA.The results of verification test show that the method mentioned in this paper could pick up the fundamental voltage positive & negative sequence component and obtain the information of fundamental voltage frequency and phase when the a.c.network rising voltage asymmetry and distortion

etc.The method can meet the requirements of active power filter for voltage frequency and phase real-time detection

and control & protection.