I. Introduction
Harnessing solar energy has been as a way to mitigate the issues of energy crisis and globe warming. The PV industry is growing very rapidly, the annual growth rate is more than 40% for the last decade [1]. In the present market, power electronics system is mainly designed for centralized two-stage inverter configuration. This centralized inverter achieves the function of MPPT, DC/AC inversion and AC interface to grid. The power losses are normally high in this configuration, mainly due to the mismatch losses between the modules and repeated power processing. If any of the modules in the string failed, the whole string or even the whole system has to be shut down. Those problems limited the development of the PV industry [2].