Design of a High-Performance High-Pass Generalized Integrator Based Single-Phase PLL
For designers of grid-interactive power converters, this work offers a computationally efficient PLL with fixed parameters that mitigates DC offsets, harmonics, and frequency deviations, but it is an incremental improvement over existing SOGI-based PLLs.
This paper presents a single-phase PLL based on a modified second-order generalized integrator (SOGI) that eliminates the effects of input DC offsets, achieving high-pass filtering. The proposed HGI-PLL achieves the fastest transient response among SOGI-based PLLs with DC cancellation, limiting unit vector THD to within 1% under specified non-ideal conditions.
Grid-interactive power converters are normally synchronized to the grid using phase-locked loops (PLLs). The performance of the PLLs is affected by the non-ideal conditions in the sensed grid voltage such as harmonics, frequency deviations and dc offsets in single-phase systems. In this paper, a single-phase PLL is presented to mitigate the effects of these non-idealities. This PLL is based on the popular second order generalized integrator (SOGI) structure. The SOGI structure is modified to eliminate of the effects of input dc offsets. The resulting SOGI structure has a high-pass filtering property. Hence, this PLL is termed as high-pass generalized integrator based PLL (HGI-PLL). It has fixed parameters which reduces the implementation complexity and aids in the implementation in low-end digital controllers. The HGI-PLL is shown to have least resource utilization among the SOGI based PLLs with dc cancelling capability. Systematic design methods are evolved leading to the design that limits the unit vector THD to within 1% for given non-ideal input conditions in terms of frequency deviation and harmonic distortion. The proposed designs achieve the fastest transient response. The performance of this PLL has been verified experimentally. The results are found to agree with the theoretical prediction.