Evaluation of Quadrature Signal Generation Approaches for Single-Phase Electric Aircraft Grids

This article evaluates non-adaptive orthogonal signal generation (OSG) approaches to understand their suitability for single-phase electric aircraft (EA) grids. It is noteworthy that the OSG approaches are widely accepted filtering approaches solving the problem of accurately estimating the grid parameters, i.e., amplitude, phase, and frequency. Also, the limited information provided by the single-phase grid voltage signal can be elevated with better filtering capability such that phase-locked loops (PLLs) and frequency-locked loops (FLLs) can perform better under distorted grid voltage conditions. Keeping in view that the non-adaptive OSG approaches do not involve frequency feedback loops, thus demonstrating fast extraction of fundamental orthogonal signals, are considered for further investigation. However, the issue is that not all the OSG approaches are suitable for single-phase EA grids owing to the broader frequency variation range, i.e., 360 Hz to 900 Hz. Hence, it affects the dynamic performance abilities of PLLs and FLLs under wider frequency variations. Furthermore, unlike the utility grid, any OSG approach tuned and designed at the nominal frequency of the EA grid, i.e., 400 Hz, will not yield proper magnitude in the output and are prone to phase errors. Therefore, in this research, non-adaptive approaches are documented employing computationally simpler error correction approaches that can help estimate the error-free amplitude and phase information. The numerical and experimental investigation reveals that the EA grid-connected converters and active power filter applications can take advantage of the utility grid OSG approaches.