A Novel Predictive Approach to Direct Power Control of a Grid Connected Multilevel Converter

In this paper a novel approach for direct power control (DPC) of a grid connected 3-level voltage source inverter (VSI) is presented. This method is based on a decision strategy, which selects the best appropriate converter voltage vector for the next sampling period in order to precisely track the active and reactive power references. To predict the VSI voltage vector, a discrete model of the system is derived. Using the discrete model, the voltage vector which minimizes a specific quality function will be selected. Due to a large number of voltage vectors available in the output of a 3-level converter and in order to reduce the computation time, a classification of available voltage vectors based on the grid voltage status has been done. The performance of the proposed predictive control method is compared with classical solution (VOC) via extensive simulations. The results show that the predictive method effectively controls the active and reactive powers and performs very well compared to the VOC. This predictive method improves the transient response and keeps the steady-state harmonic spectrum in an acceptable level.