Analysis of three-phase magnitude-phase detection method based on double dq transformation

The detection method of voltage for control of reactive power is an important issue because stability of voltage affects the operating characteristic and security of power grid when large wind generator integrated into the grid. The conventional three-phase magnitude-phase detection method of voltage, which adopted PI control method, had a low speed of dynamic response because of negative-sequence and harmonic components. Also it could not exactly extract the fundamental positive-sequence magnitude/phase of a three-phase power system. Based on double dq synchronous reference frame, a novel three-phase magnitude-phase detection method which can decouple the positive dq and negative dq sequences and detect the magnitudes/phases of fundamental positive-sequence component and negative-sequence component of three-phase voltages or currents has been proposed. The simulation results approved that the response speed of proposed method is more quickly than the conventional method. In addition, the magnitudes and phases of the fundamental positive-sequence voltage could be tracked more accurately and detecting precision be higher by suppressing harmonic propagation effectively with new method.