Disturbance Rejection Ability Enhancement Using Repetitive Observer in Phase-locked Loop for More Electric Aircraft

Under the concept of transportation electrification, more electric aircraft (MEA) involves more electrical energy to reduce emissions. Phase-looked loops (PLLs) have been well developed for synchronizing different power sources in a grid. Since MEA operates at variable frequency from 360 Hz to 800 Hz, a third-order model based steady-state linear Kalman filter PLL (SSLKF-PLL) has been proposed in literature to achieve fast tracking performance during such grid frequency variations. To suppress the potential disturbances due to harmonics in the grid, sensor scaling errors/unbalances and d.c offsets while maintaining low computational burden, this paper aims to enhance the disturbance rejection ability of SSLKF-PLL by adding a repetitive observer (RO). Simulation tests show that RO allows stable and effective suppression of disturbances from all above-mentioned sources during variable frequency operation.