Implementation and investigation of a solar and wind energy-based grid-connected hybrid system with nine switch converter

Abstract

In this paper, a hybrid, comprising of solar-PV and wind energy sources, grid-connected system with nine-switch converter (NSC) instead of a back-to-back (BtB) converter (comprising 12 switches) is proposed and a control scheme is also proposed for NSC. NSC is the potential substitute for the current BtB converter, which uses 12 switches. The NSC uses nine switches, that is, three less active switches than BtB converter therefore the system efficiency is increased by lowering component costs, counts of components, and switching losses. Vector control concept is considered to design the proposed control scheme for NSC to provide both supply power generation to the utility grid at unity power factor and variable speed constant frequency operation under fluctuating wind velocity and solar irradiance. In addition, 120° discontinuous modulation concept is integrated with the control scheme of NSC for reducing the switching losses of the system. Moreover, maximum power point trackers are used for capturing maximum power from wind and solar-PV, and blade pitch angle algorithm is also considered to restrict the generation from wind to its rated power level while speed is more than its rated level. The proposed system along with its control scheme is implemented in OPAL-RT lab to investigate its performance thoroughly under real-life scenarios (i) constant solar irradiance and variable wind velocity and (ii) variable solar irradiance and wind velocity. Results show the effectiveness of the proposed scheme on the system and it has been observed that the proposed scheme provides good dynamic responses in terms of less oscillation during transient, almost negligible (i.e. 0.0001 approx.) steady-state error etc. to the variation of input sources.