An effective feed-forward approach for suppressing low order current harmonics of grid-connected VSCs

Improper control of grid-connected Voltage Source Converters (VSCs) in harmonically polluted grid results in flowing low order current harmonics into the grid. In other words, the VSC behaves as harmonic load from grid point of view. VSC output filters cannot eliminate these polluted currents, since they are designed for switching high frequency harmonics. From the approaches presented in this regard, feed forward compensation of grid voltage is the common method which decouples the VSC behavior from the grid voltage including its harmonics. However, time delay in control of VSC imposed by computations and PWM switching affect performance of this method. In this paper, a modified feedforward scheme considering the time delay of VSC is proposed to eliminate these harmonic currents. Performance of the proposed method is verified through simulations.