Performance enhancement of grid connected PWM rectifier under grid disturbances

Abstract

The voltage distribution system may be disturbed in spite of a stiff system. The front end rectifiers should be controlled to provide immunity to such disturbances. In this paper, virtual flux oriented control algorithm for three phase active rectifier under distorted and unbalanced grid conditions is presented. No voltage measurement is required to implement this control scheme. In spite the grid virtual flux is estimated. The control is based on grid virtual flux estimation without ac voltage sensors. The LCL filters have been acknowledged for reduction in harmonics at switching frequency. However the selection of LCL parameters is tedious task. A complete design for the active rectifier and LCL filter has been given in detail. The virtual flux is utilized to get the voltage and instantaneous power estimation. As the flux is less sensitive to grid voltage disturbances so it provided more robust control of the converter. The control algorithm is simulated in MATAB under two conditions: (a) normal grid voltage and (b) unbalanced and distorted grid voltage. The results demonstrate the balanced and sinusoidal grid current even under grid unbalanced and distorted grid voltages.