Virtual-Flux-Based Predictive Direct Power Control of AC/DC Converters With Online Inductance Estimation

This paper presents an improved predictive direct power control (P-DPC) algorithm for grid-connected three-phase voltage source converters without AC-side voltage sensors. The new algorithm is based on virtual-flux (VF) estimation and operates with constant switching frequency. Predictive controller selects in every sampling period appropriate voltage vector sequence and calculates duty cycles in order to minimize instantaneous active and reactive power errors. The theoretical principles of this algorithm are discussed, and selected experimental measurements and scope graphs that illustrate the operation and performance of the system are presented. It is shown that VF-P-DPC algorithm exhibits several advantages, particularly sinusoidal-grid-current low harmonic distortion even when grid voltage is distorted. In addition, the algorithm provides high dynamics at low switching frequency of 2 kHz.