Adaptive Rectification Current Observer for slim DC-Link AC Drives with Unknown Input Voltage

The paper focuses on estimating the rectifier current in slim DC-Link AC drives, known for their reduced DC-Link capacitance. Particularly, at full load, the capacitor’s filtering effect on the input voltage diminishes. This allows the estimation of the input voltage from DC-Link voltage measurements. We adopt a simplified model, treating the drive as a DC-Link that supplies a constant power load. Notably, the model accounts for the equivalent series resistance (ESR) of the capacitor, adding intricacy to the design. We propose an adaptive observer to estimate both the rectification current and the input voltage. We design a Luenberger state observer with output injection terms. The study on the observer stability is based on decoupling the state estimation errors from the input estimation errors through swapping design. Theoretical developments are validated through numerical simulations.