Disturbance observer based robust voltage control of photovoltaic generator interfaced by current mode buck converter

In this paper, a new control method for photovoltaic generator is presented. The novel method is implemented on photovoltaic generator charging a battery storage system thru buck converter. The controller tasks are re-shaping the buck plant converter, and cancel its right half-pole while keeping tight reference tracking and disturbance rejection. Moreover, the integrated system of generator-converter-load possesses nonlinear behavior due to the varying environmental conditions and the boundaries of photovoltaic generator versus battery state of charge, as revealed from an analysis of small-signal equations for possible unstable condition. It was shown that system constrains consequence in a complicated control task where standard controller of an inverse plant is insufficient to stabilize the system. Then a proportional integral controller is implemented. However, it is shown that varying closed-loop performance from over-damped to under-damped, depending on the operating point. Eventually utilizing a robust disturbance observer controller reveals that closed-loop performance remains nearly nominal throughout the entire operation range.