Discrete Polynomial Current Controller for a Three-Phase VSC Connected to the Grid using a LCL Filter

This paper proposes a new design approach to the currents controller of Voltage Source Converters (VSC) connected to the power grid using a LCL filter. By developing a system model in the discrete domain and by using complex numbers, the proposed approach deals simultaneously with: the cross coupling components of the currents model in the synchronous referenced frame; the time delay between the currents acquisition and the PWM actuation; the issues related to the LCL filter resonance. The controller is easily tuned as the designer only needs to specify the required settling time. The controller architecture avoids the need of damping techniques to deal with the filter resonance. Robustness against grid filter parameters variation is also a characteristic of the proposed controller.