Evaluation of low frequency input current ripple in a non-isolated single phase photovoltaic grid-connected inverter with back current gain model

Due to power time-varying characteristic of a single phase photovoltaic (PV) grid-connected inverter in grid side, its front-end dc/dc converter tends to draw a large ac ripple current with double grid frequency, which would decrease maxim power point tracking performance of PV side. A novel method is proposed for the low frequency input current ripple analysis of a boost converter in a non-isolated single phase PV inverter, based on back current gain A_i(s) (input current to output current) model. Mathematical models with different control schemes are built and derived, which are verified in SABER environment. It is indicated and proved that average current mode control strategy is more effective than voltage mode control and open loop control methods. Design principles are also presented. Simulation and experimental results are provided for model verification. Bandwidth limitation is also discussed and improved with proposed PR controller with A_i(s) model.