Synchronous frame and resonant adaptive observers as disturbance estimators and their applications in power electronics

This paper presents a theoretical framework for disturbance estimation using synchronous frame and resonant adaptive observers. These observers are well suited to estimate steady state sinusoidal disturbances with zero amplitude and phase error, compared to stationary frame observers. Construction of such observers is simple, without augmenting the number of states of the observer, which enables easy implementation. Since frequencies of the disturbances can change over time and are usually not known a priori, these observers are constructed so that they can adapt to the frequencies of the disturbances. Practical applications discussed in the paper are grid voltage estimation in grid connected voltage source converters (VSCs) and back-emf and rotor flux estimation in induction machines, where both are treated as disturbances. Simulation and experimental results prove the theoretical concepts.