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

•Disturbance observer based robust voltage control of photovoltaic generator interfaced by buck converter is proposed.•Exploiting disturbance observer as a counteraction to the nonlinear loop regulation variables.•The method robustify voltage control loop with consideration to the possibility of unstable Pole. 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.