Novel Single-Loop Control Strategy for 400 Hz Voltage Source Inverter with LC Filter

The control of 400 Hz Ground Power Units (GPUs) in the range of several hundreds of kW poses distinct challenges, as the switching frequency (fsw) must be constrained to limit switching losses. This constraint typically results in low ratios of the switching and LC filter natural frequencies (fn) relative to the fundamental frequency. Notably, without mitigation, such systems often face stability issues or non-minimum phase behavior when fn<fs/3 (where fs is the sampling frequency). To address these challenges, this paper introduces a single-loop voltage control strategy for a 400 Hz voltage-source inverter (VSI) featuring a robust voltage decoupling scheme. Crucially, this decoupling allows the system to maintain minimum phase characteristics and operate with positive gains even when fn<fs/3, effectively solving the stability problems inherent to this operating region. The proposed architecture employs a proportional-resonant (PR) controller, with parameters systematically tuned to achieve maximum system damping based on stability regions dependent on the ratio between the sampling and natural frequencies. Validated through simulation and experimental procedures, the proposed method demonstrates precise voltage tracking and a robust dynamic response, proving its suitability for high-power, high-fundamental-frequency applications.