Control and estimation scheme for PV central inverters

Photovoltaic (PV) systems that inject energy directly to the grid have attracted much attention over the last years due to their lower cost per watt with respect to other photovoltaic applications and the incentives that governments offer for such systems. In a grid-connected PV system a power inverter is required to optimize the energy transfer from the photovoltaic modules to the power grid. Considering the nonlinear time-varying nature of grid-connected PV systems allows to obtain well-defined mathematical description of the problem that can be useful for the design of control schemes. Nevertheless, control structures that explicitly take into account the non-linear electrical model of the PV modules usually depend on parameters that are unknown and/or difficult to measure. Consequently, such controllers should normally be used with estimator schemes. In the present paper a control and estimator scheme for a full-bridge central PV inverter which is valid for a wide range of PV technologies is presented. As shown with a simulation study, the required control objectives have been achieved and the unknown temperature dependent have been correctly estimated.