Robust current control design of Voltage Source Converter under unbalanced voltage conditions

This paper presents a robust current control design method to improve the performance of Voltage Source Converter under unbalanced grid voltage conditions. Unbalanced grid voltage would increase the low order harmonic distortion of the converter´s input current, power and DC voltage. Current compensation strategies are derived in both synchronous and stationary coordinates based on instantaneous power theory. The control object is to suppress the oscillations in current or power. The current controller is developed in the unified frame of H∞ control theory. Proper weight functions are chosen for each coordinate. Simulation results revels the feasibility of the proposed control method.