کنفرانس بین المللی ماشین و محرکه های الکتریکی

صفحه اصلی / The 5th International Conference on Electrical Machines and Drives

On the effect of control parameter variations and PLL dynamics on low-order harmonics in single phase grid-connected inverters in the presence of grid impedance uncertainty

نویسندگان :

Seyed mohammad ebrahim Mirjebreili¹ Sadegh Mohsenzade²

1- Department of Electrical Engineering K. N. Toosi University of Technology 2- Department of Electrical Engineering K. N. Toosi University of Technology

کلمات کلیدی :

Grid-connected inverter،Phase-locked loop (PLL)،Output impedance،Stability analysis،Total harmonic distortion (THD)،Renewable energy

چکیده :

This research models and analyzes the stability of a single-phase grid-connected inverter, focusing on its dynamic behavior at frequencies higher than the fundamental 50 Hz grid frequency. In practical applications, fluctuations and uncertainty in the grid impedance may cause inverter instability and result in the generation of low-order harmonics in the output current, particularly the 3rd, 5th, 7th, and higher orders. To address this issue, the inverter is modeled in the extended frequency domain, and its output impedance is derived and analyzed. Using the Nyquist stability criterion, the dependence of output current stability on inverter and grid impedance interactions is investigated. The study further examines how tuning the PI parameters in both the current control loop and the phase-locked loop (PLL) can enhance inverter stability and suppress low-order harmonics. Simulation results confirm that proper PI and PLL adjustment not only guarantees stable operation but also effectively eliminates the dominant low-order harmonics, thus decreasing the total harmonic distortion (THD) present in the inverter’s output current.