DC voltage sensorless control strategy for three-phase grid-connected inverter

For a small distributed generation (DG) system, low price, high performance, and high reliability are three important factors required to make the system marketable. In this paper, to acquire a cost-effective DG system, a comprehensive control scheme with a proportional-integral (PI) current controller, a predictive algorithm, and real-time sampling techniques is presented to control a three-phase grid-connected inverter for a DG system. Based on the predictive and real-time sampling schemes, the required output voltage vector of the inverter can be accurately predicted by measuring the grid voltage and the inverter output current. The current PI controller is used creatively to obtain the DC voltage (Vdc) information without any Vdc sensors. Test results show the output current of the inverter is of high quality by this DC voltage-sensorless technique.