A Hybrid Modular Multilevel Converter For Solar Power Integration

A Hybrid Modular Multilevel Converter for Solar Power Integration

Abstract_

 A Hybrid Modular Multilevel Converter (H-MMC) for grid-connected Photo-Voltaic (PV) system is presented in this paper. The array of PV-panels is connected in each sub-module of the converter. The sub-modules are connected in series to form the DC-link for each phase. The DC-link voltage is unipolar and multilevel in nature which is converted to AC voltage by a Low Frequency Converter (LFC). This topology can be applicable at high power by increasing number of sub-modules per phase. The hybrid-MMC has many advantages compared to conventional MMC, e.g. more voltage levels, less capacitor count, no circulating current, higher efficiency and less foot-print. A global Maximum Power Point Tracking (MPPT) algorithm is proposed for this converter which requires the voltage and current signals of only one submodule. The limitations of global MPPT under partial shading is overcome through distributed MPPT. A least-MPPT algorithm is presented to make the three phase powers balanced under non-uniform partial shading among the phases. The usefulness of this converter configuration with two different MPPT algorithms (global and distributed) are investigated through MATLAB/SIMULINK simulation.