Predictive Direct Power Control Strategy for Grid-Connected VSI

Abstract

A key limitation of the lookup table-based direct power control strategy is that the switching frequency varies with the distinct active and reactive powers combinations, resulting in an undesirable broadband harmonic spectrum range. The current study introduces a direct power control that is based on predictive approach (P-DPC) for grid-tied VSI. This approach is established through the fusion of the DPC technique and the predictive one, providing high dynamic performance and constant switching frequency. Rather than applying one voltage vector in the DPC scheme, the recommended P-DPC makes use the sequence of voltage vectors throughout a switching period. The strategy's principle involves two essential steps. The first one consists to determine the adequate sequence of vectors which contains zero and non-zero vectors and then to arrange them so that switching losses are kept to a minimal while still supervising the exchanged powers with the grid. Secondly, the power errors are eliminated by the prediction of the duration times. A grid-connected inverter model is used for numerical testing to validate the feasibility of the suggested P-DPC algorithm. The obtained results show high steady state and dynamic performances.