An integrated inverter with maximum power tracking for grid-connected PV systems

An inverter for grid-connected photovoltaic systems is presented in this paper. It can globally locate the maximum power point of the panel over wide insolation and feed the solar energy to the grid. Its structure mainly integrates a previously developed maximum point tracking method and output current shaping function into a buck-boost-derived converter and then inverts the shaped current through a grid frequency bridge to the grid. Instead of having a storage capacitor connecting in parallel with the converter output, series connection is used, so that the required capacitor voltage rating is lower than that in classical inverters. Most importantly, the inverter output current harmonics are less sensitive to the capacitor value. A 30W laboratory prototype has been built. The tracking capability, inversion efficiency, and large-signal responses at different insolations have been investigated. Detailed analysis on the inverter performance has been performed. The theoretical predictions are verified with the experimental results.