Observer-based nonlinear controller for a three-phase Voltage-Source Converter feeding a constant power load

In this paper an observer-based controller for voltage source converters (VSCs) feeding constant power loads is introduced. The observer is used for estimating the power load and this estimate is feed forwarded to build a nonlinear controller in order to improve the whole system performance. The proposed observer presents linear error dynamics. The main advantage of our proposal is that linear error dynamics allows to design the observer by using linear techniques. In this way, the observer transient performance (i. e. speed of convergence) is clearly established in the whole range of VSC operation. The feedback controller is based on input-output feedback linearization considering an energy output. In this way, complete input-output linearization is obtained such that linear control strategies can be used in outer loops. Simulation results including performance in presence of commutation frequency, measurement filters delays, and parameters uncertainties are presented to validate the proposed technique.