An Analysis of Direct Power Control for Three Phase AC-DC Converter

This paper investigates a virtual flux control for reducing the number of sensors in the direct power control of a three phase ac-dc voltage source converter. The usage of input ac voltage sensors to determine the grid voltage angle for synchronization and estimation of the instantaneous active and reactive powers, are avoided by applying a virtual flux concept in the control scheme. The virtual flux control technique is used to extract the grid voltage from the converter switching states, dc output voltage, and line currents. An improved virtual flux direct power control utilizing the new switching table has been proposed in this work. The switching table is developed based on the instantaneous power derivative method which relies on the sign and magnitude of the change in instantaneous active and reactive powers. The steady state as well as dynamic performances of the proposed system are presented and analyzed by means of Matlab simulation and experimental verification.