Analysis of the Application of Polynomial Reference Tracking Generalized Predictive Control in the Control of an LCL Filter

LCL filters are widely used to connect a renewable electrical power source to the electrical grid. The optimal power transfer to the grid depends on the tracking of a sinusoidal current reference synchronized to the grid voltage. However, the tracking of that reference is a difficult task. On the other hand, the sinusoidal reference can be considered as composed of a set of polynomials of different degrees. Thus, this paper explores the application of polynomial reference tracking generalized predictive controller (Poly-GPC) to control the output current of the LCL filter connected to an AC grid. Different tests using the Poly-GPC with different polynomial reference degrees were performed to verify the relationship between the polynomial degree used to approximate the sinusoidal reference with the control accuracy. Simulation results show that the Poly-GPC can be used to control an LCL filter. An analysis of the effect of the polynomial order used to approximate the sinusoidal reference in the current reference tracking is done. The Poly-GPC adds integrators to the control system to reduce the tracking error. It was observed that adding too many integrators may create instability. However, a low number of integrators reduces the tracking performance.