VIRTUAL GRID FLUX ORIENTED CONTROL METHOD FOR FRONT-END THREE PHASE BOOST TYPE VOLTAGE SOURCE RECTIFIER

This paper investigates a new approach to adapt the conventional voltage oriented control (VOC) for the front-end pulse width modulation (PWM) three-phase boost type voltage source rectifier that is applicable for low and medium power voltage source inverter (VSI) system applications. The usage of grid voltage sensors to determine the voltage angle for synchronization and voltage amplitude for the controller, are avoided by applying a grid virtual-flux (VF) concept. The virtual-flux method is used to extract the grid voltages from the converter switching states, dc output voltage, and line currents. Subsequently, virtual grid flux oriented control (VFOC) with the improvement of virtual-flux estimation method has been proposed in this work. The steady state as well as dynamic performances of the proposed system are presented and analyzed by means of the Matlab simulation. The PWM rectifier utilizing VFOC is able to produce adjustable output voltage, fix switching frequency, near unity power factor and low harmonic distortion of the line currents.