Improved Instantaneous Derivation dq Detection Voltage Drop Method

Aiming at the power quality problem of voltage dynamic drop caused by the intermittent output of a large number of distributed power sources (DG) in micro-grid, an instantaneous derivation dq algorithm combined with delay-free finite impulse response (FIR) digital filtering is proposed. Based on the phase-locking method of FIR digital filter and "zero-crossing phase-detection", it is applied to the phase-locked control of instantaneous dq transformation. The traditional instantaneous dq transform is delayed by 90° from the single-phase voltage signal to change the αβ coordinate to a single-phase signal. The differential β-coordinate is used to form the αβ coordinate, and the delay-free FIR digital filter is used to replace the low-pass filter of the conventional instantaneous dq, and the filter is filtered. Before the link is preset, the non-fundamental components in the signal are filtered out and then the instantaneous derivation dq transform is performed. The FIR digital filtering algorithm combined with the instantaneous derivation dq algorithm realizes the voltage sag amplitude, phase abrupt change and voltage dynamic change start and stop time of the micro-grid. Finally, the micro-grid model is built by PSCAD/EMTDC simulation platform, the fault type and harmonic source are set, and the instantaneous derivation dq algorithm combined with FIR digital filter is compared with the traditional voltage sag method. The simulation results show that the instantaneous dq derivation algorithm combined with FIR filtering has better real-time performance, and the recognition effect of the power quality problem of the voltage sag caused by the distortion voltage is improved, which satisfies the dynamic voltage restorer (DVR) voltage. The real-time and reliability requirements of the inspection.