Control of a Multiport Converter for Independent MPPT Algorithms and Grid Integration in Photovoltaic Applications

The advantage of multiport dc-dc converters over a configuration of several two-port dc-dc converters with a common dc bus is the reduction in the number of components. However, certain multiport dc-dc converter topologies still present significant challenges, such as cross-coupling. This article introduces a two-stage system composed of a dual-input single-output dc-dc converter for dual MPPT, linked with a single-phase full-bridge inverter for grid integration. The mathematical model and digital control strategy based on state variable feedback and decoupler are presented to regulate the voltages of the photovoltaic modules. The results show a maximum deviation of voltage <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>pv</i>1</sub> of 2.47% when there are variations of 6 V in the reference voltage in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>pv</i>2</sub> and a maximum deviation of voltage <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>pv</i>2</sub> of 6.7% when there are variations of 4 V in the reference voltage in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>pv</i>1</sub>. These outstanding results enable independent and flexible MPPT algorithms to operate stably under different environmental conditions. With respect to the experimental results, they show that the proposal can operate independent MPPT algorithms between two PV modules with reduced cross-coupling, and it is also possible to regulate the dc-link voltage and the grid current under different conditions.