This paper proposes a method of three-phase voltage phase and frequency locked loop under distorted voltage conditions like voltage dip, frequency mutation, phase mutation, harmonics injected. After positive(negative) dq synchronous coordinate transformation, the dq axis voltage component contains AC component whose frequency is 2ω(-2ω)，which is caused by negative (positive) voltage component. After the dq axis DC voltage component extracted from negative (positive) sequence dq synchronous reference frame transformation compensates positive (negative) sequence dq transformation synchronous reference frame voltage component, decoupling structure is built. Meanwhile, by designing low-pass filter reasonably, harmonics are filtered, so that positive-sequence fundamental component can be extracted from three-phase voltage. The simulation result shows that, this method can make it that the frequency and phase of positive-sequence fundamental voltage can be locked faster and more accurately.
