A novel hybrid SPLL for polluted grid environment

Software Phase-Locked-Loop (SPLL) is a kind of servo mechanism to adjust system´s output synchronized with one reference signal. The polluted grid voltage is not only unbalanced, but also contains large quantities of low order harmonics. In this case, SPLL still can obtain fundamental positive sequence component (FPSC) effectively and realize synchronization with grid rapidly and accurately, that is one of the key factors for distributed power generation systems. Multiresonant Second-Order Generalized Integrators (MSOGI) and Multiple Complex Coefficient Filter (MCCF) are two kinds of synchronization technologies under polluted grid environment. However, it will largely need to design either SOGIs or CCFs corresponding to each order harmonic when considering some more harmonics, thus resulting in more complicated structure. This paper proposes a novel hybrid SPLL structure, named HDMCS-SPLL (Hybrid DSC, MCCF and SOGI): its pre-stage input after delayed processing can be divided into two large clusters. As only one contains FPSC, it just needs to design targeted CCFs to damp harmonic components in this cluster. Thereby reducing unnecessary design complexity and mitigating coupled interference between each harmonics. Meanwhile, existing DC bias could be suppressed by its SOGI module. Finally, simulation results show that proposed SPLL structure can extract FPSC fleetly from high polluted grid voltage, and it also performs better steady and dynamic performance than PLLs based on MSOGI or MCCF structure. Proposed structure is more applicable to polluted grid environment.