Control of high-performance AC power supplies using adaptive digital filters

This paper investigates the use of adaptive digital filters for improving the performance of the inverter stage control of AC power supplies. In the proposed solution a conventional multi-loop control is used in order to ensure a fast dynamic response due to step load changes and a feedforward control based on adaptive filters is used in order to reduce the output voltage distortion in steady-state. One of the main properties of the proposed approach is the automatic tuning of the control coefficients so as to minimize the steady-state errors on the output voltage due to system disturbances, such as dead-times, dc link voltage ripple, and load variations. Because of the use of only few coefficients in the digital filters, the control remains quite simple and fully compatible with commercial muC or low cost DSP. One of the main disadvantages is the lack of analytical tools for stability analysis so that an accurate control parameter tuning is needed to ensure stability in any operating conditions. Experimental results on a single-phase 2kVA prototype show the properties and limitations of the proposed approach.