Abstract
This paper proposes a modular inverter based on Cuk converters for solar photovoltaic (PV) systems to mitigate the voltage and current mismatch issue at the PV module level. The proposed modular Cuk inverter (MCI) is formed by connecting several low-voltage (LV) microinverters (MIs) in series and linking their output sides to the distribution network. This architecture does not require a central inverter, and hence, it eliminates the need for large dc-link intermediate capacitors. The proposed MCI provides more controllability over the PV system by having a decentralized structure. The MCI will improve the PV system efficiency by reducing the voltage and current stresses in the MIs and will enable better voltage regulation due to the provided controllability. Since the proposed MI topology is based on the Cuk converter, it offers continuous input and output currents that will reduce the required filtering capacitance and will provide a wide range of voltage regulation for either supplying the loads or charging the storage batteries. The paper presents the associated control scheme for the proposed MCI that employs two controlling loops. The input loop at the PV side is designed and tuned to eliminate the ripples from the input current, while the outer loop at the grid side will control the output ac current and hence the MCI power. Computer simulations are presented using MATLAB/SIMULINK software to examine the validity of the suggested inverter for distributed generation PV residential applications. A scaled-down experimental prototype controlled by TMS320F28335 DSP was built and used to validate the mathematical analyses and simulation results.