Optimal Indirect Power Predictive Controller in the Alpha-Beta Reference Frame for Grid-Connected Converters

This article presents an indirect power predictive optimal controller applicable to grid-connected converters. The VSI converter is used as an interface between distributed generators, energy storage systems and the ac-grid. The objective of the research project is to develop a controller with high static and dynamic features, that performs with low computational burden and low switching stress. The first step to develop the controller is to select the appropiate reference frame. The $\alpha\beta$ frame is used for its simple structure and easy implementation. Then, the proposed methodology consider the controller performance to define the sampling period, the prediction horizon and the switching pattern. Results show that an increment in the sampling period results in a major harmonic content, and if the prediction horizon increases, the number of calculations is higher without improving the controller performance. The main features of the proposed controller are: low sampling times and a two-steps prediction horizon. With these features the VSI efficiency rises, while the systems's losses and harmonic distortion are reduced.