Reduced 2nd Harmonic Input Current Ripple Quasi Z-source Microinverter for On-Grid PV Power Conversion

Abstract

Direct connection of PV modules to the grid using microinverters has been gaining interest due to their intrinsic modularity and increased energy harvesting potential. However, since microinverters are essentially single-phase converters, a large second harmonic current component is drawn from the PV module, thus difficulting following its maximum power point, impacting power generation capability and overall efficiency of the system. To tackle these issues, a modified single-stage quasi-Z-source microinverter topology is presented, in which the qZS impedance network is modified by magnetically coupling its inductors. It is shown through analysis and simulations that this modification has the effect of blocking most low-frequency components from the current drawn from the PV module, making it almost DC. This along with its single-stage construction, high voltage gain, and reduced component count results in a high-performance solution.