Equivalence-based tuning of ADRC- and SRF-PLLs for grid-connected systems

AC-DC power conversion is fundamental to grid-connected consumer technology, where phase-locked loops (PLLs) are typically used for real-time parameter estimation. This paper demonstrates that a linear active disturbance rejection control (ADRC)-based PLL is dynamically equivalent to a conventional synchronous reference frame (SRF)-PLL equipped with an inloop low-pass filter (LPF). This equivalence is established analytically through small-signal modeling and parameter mapping. Using bandwidth-parameterization-based tuning for the ADRC-PLL, equivalent proportional-integral (PI) control gains and LPF cut-off frequency for the SRF-PLL are derived analytically, while the inverse mapping–including cases based on the symmetric optimum method–is performed numerically by solving a third-order polynomial equation. Theoretical findings are validated through experimental results using a grid-connected AC-DC PWM rectifier. When tuned under equivalent conditions, both PLLs exhibit nearly identical dynamic performance. Experimental tests under non-ideal grid conditions reveal a performance trade-off: the ADRC-PLL offers greater robustness to high-order harmonics, whereas the SRF-PLL demonstrates superior performance under low-order distortion and voltage unbalance. These results provide a unified framework linking ADRC and SRF-PLL formulations, supporting the design of advanced PLL architectures that combine the strengths of both approaches.