Research on Harmonic Detection Technology in Power Grids Based on Improved Phase-Locked Loop

With the large-scale integration of distributed generation into the power grid, issues such as frequency fluctuations, voltage imbalance, and harmonic distortion in power systems have become increasingly severe. Under such unbalanced and distorted grid conditions, the traditional <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$i_{p}-i_{q}$</tex> harmonic detection method can no longer meet engineering requirements. Addressing problems such as harmonic distortion and DC components under non-ideal grid voltage conditions, an improved <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$i_{p}-i_{q}$</tex> harmonic detection algorithm is proposed. This algorithm integrates an enhanced second-order generalized integrator (SOGI) filter into the conventional ip-iq harmonic detection loop. By doing so, it enhances the ability to filter out DC components and harmonics. Simulation results demonstrate that the improved phase-locked loop (PLL) can quickly lock onto the frequency under non-ideal grid voltage conditions, while effectively filtering out high-frequency signals and DC components. Furthermore, the current distortion rate detected using the new <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$i_{p}-i_{q}$</tex> algorithm is significantly reduced.