New design for photovoltaic systems

Generally, photovoltaic (PV) systems have two independent controls: (1) DC control for the DC/DC converter to track the maximum power point of the PV array; and (2) AC control for the DC/AC converter to feed, efficiently, the load attached to it. This paper shows how to design a global control, using vector control (field orientation in an AC engine), avoiding use of the DC/DC converter, and finding the relationships among the DC magnitudes and AC ones. So, only the inverter is necessary to control the PV array and the AC load. Two cases are considered: pumping with an asynchronous machine and connecting to the grid systems. One 10 kW prototype has been built to validate the theory. It has been successfully tested in a laboratory. The total system has was finished and installed in February 1998, first results will be available at the end of 1998