Improvement of Ventilation Drive System with Solar Power and a Voltage Level Based Control Structure

Ventilation systems are one of the applications in which the load profile matches very well with the solar generation profile. Therefore, complementing ventilation systems with photovoltaic power has the potential to both reduce the carbon footprint and improve the cost effectiveness of the system. In this work, a grid-connected ventilation system has been improved by connecting a PV string to the common DC-link of the drive through a DC/DC boost converter, which has been designed, built and tested for this application. A control structure that manages the power flow between grid, PV string and the load based on the voltage level of the common DC link has been implemented. As no DC/AC conversion is necessary in the PV system, a DC/DC boost converter is sufficient to interface the PV string to the DC bus of the fan drive. This is simpler and cheaper compared to a conventional PV inverter and in this configuration, the DC/DC boost converter is not subject to any regulations provided by the grid utility companies. The efficient operation of the DC/DC converter and the flexible operation of the system has been experimentally demonstrated for several operation modes combining the grid and the solar power. The results show that the voltage level control was able to balance the grid, PV and load demands in all operating conditions.