Dc voltage sensorless control method for three-phase grid-connected inverters

A novel dc-link voltage sensorless technique for a three-phase grid-connected inverter is presented. Based on predictive and real-time sampling schemes, the required pulse width modulation (PWM) output voltage vector is accurately predicted by measuring the grid voltage and the inverter output current. A q-axis current proportional-integral (PI) controller is also used. The controller forces the output current to accurately follow its reference, and is also used to derive the dc-link voltage. By using this method, the dc-link voltage is not obtained from a voltage sensor, but instead is obtained from inverter output current information. Test results show that the output current of the resultant inverter is of high quality at steady state and can follow its reference quickly in dynamic states as well.