Amplitude-Phase Detection for Power Converters Tied to Unbalanced Grids with Large X/R Ratios

Amplitude-phase information of the voltage/current phasor, which is prerequisite for grid-tied converter control and protection, can change almost instantaneously in low-voltage distribution systems with small X/R ratios. However, equivalent impedances high-voltage power are usually inductive (with large ratios), flow pertinent grids generates decaying dc (DDC) components amplitude long duration during disturbances. Therefore, ratios DDC must be fully considered amplitude-phase detection to achieve effective protection. To this end, main present transient a system after unbalanced disturbance first analyzed, general model obtained by synthesizing multimode components. Then, resorting waveform characteristics different components, an algorithm proposed based on multicomponent parallel-detection structure. Compared existing techniques, time reduced half grid cycle. Finally, iterative variable-interval integral developed, improving antinoise ability overcoming computational burden issue. This enables direct integration into converter's embedded processor. Experiment results verified effectiveness superiority technique.