Photovoltaic (PV) system under partial shading condition has been discussed by many researchers. By using the distributed PV system, one can control every PV panel independently in order minimum effect caused by panel shading and mismatching. To maximum the use of microcontroller and further to reduce the cost for the distributed PV system, research work switches to the development of multivariable MPPT technique. This paper reports the design of the power optimizer and the central MPPT controller associated with the distributed PV system. Performance test by several MPPT methods including the multi-variable particle swarm optimization (PSO) and the steepest decent method is presented. Thin film and poly-Si types of PV panels in various format connecting to the battery bank or the power grid are examined. It is found that multi-variable MPPT of the steepest decent method gives faster convergent tracking result, and therefore the tracking efficiency is improved and the transient power output variation is minimized. Distributed PV system with more than 10 PV panels using cascaded MPPT controller is also possible, which provides the flexibility of system design and the effective use of photovoltaic energy.