A design of differential decoupling phase-locked loop for unbalanced power systems

Abstract

Aiming at unbalanced three-phase power grid voltage, traditional phase locked loop was not able to restrain the negative sequence component in unbalanced grid voltage, which led to the poor accuracy of phase. Based on the traditional three-phase software phase locked loop model, the paper proposed a design of differential decoupling phase-locked loop. Through differential decoupling algorithm, the positive sequence component could be extracted from the unbalanced voltage. By this way, the ability of three phase software phase locked loop to resist unbalanced voltage had been improved. In Matlab, the improved software phase-locked loop was simulated. Compared with the traditional phase locked loop, the differential decoupling phase-locked loop was not only able to track the phase of grid voltage unbalance accurately without delay, but had excellent dynamic phase tracking performance.