Single-phase frequency detector algorithm applied to grid-connected power conditioning systems

This paper proposes a single-phase algorithm used to estimate the frequency, as well as the phaseangle of the utility grid. The algorithm uses self-tuning filters (STFs) operating in conjunction with low-pass filters (LPFs). The STFs are used to extract the fundamental components of the orthogonal voltages that represent a fictitious two-phase stationary reference frame (αβ-axes), while the LPFs are employed for frequency detection purpose. Therefore, both the STFs and the LPFs must be properly adjusted to avoid the compromising of the algorithm transient response. The operation principle of the proposed algorithm is presented, which is based on the frequency response analyses of both the STFs and the LPFs involved. Furthermore, simulation and experimental results are presented in order to validate the theoretical development, as well as verify the performance of the proposed synchronization algorithm under utility grid disturbances, such as voltage harmonics, voltage sags and swells, phase jumps and frequency variations.