A SPLL technique under unbalanced and seriously distorted grid voltage conditions

The traditional SPLL can´t accurately track the frequency and phase of the grid voltage under the condition of unbalanced and seriously distorted three-phase voltage. To solve this problem, the novel SPLL model based on Sequence Decoupled Resonant (SDR) combined with Second Order Generalized Integrator (SOGI) is proposed. By using the technic of SDR and SOGI, this design successfully achieves the separation of positive and negative sequence voltage, the extraction of fundamental voltage and a filting function. At the same time, the influence of the negative sequence component and the harmonic component can be effectively eliminated during the process of tracking the frequency and phase information. The simulation results show that the new SPLL can accurately track the frequency and phase of the grid voltage under the condition of unbalanced and seriously distorted three-phase voltage, which verify its validity and correctness.