Application of a novel soft phase-locked loop in three-phase PWM rectifier based on coordinate transformation

The mathematical model of three-phase PWM rectifier based on two-phase stationary frame is researched. In order to track voltage frequency and phase in allusion to the distortion of power network, a novel soft phase-locked loop based on frame transformation theory is put forward, by which the phase of positive-sequence fundamental component of voltage can be accurately detected under the condition that in power system the sags, harmonics, frequency variations and voltage unbalance occur. The result of simulation and experiment show that this novel phase-locked loop can track changes of system frequency quickly. So it has the supervised meaning on engineering.