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In this paper, a two-stage powerelectronics topology is presented for use in a BIPV module-level converter, connected to a low-voltage DC microgrid. The converter is built up as a cascade of two topologies, being an interleaved boost converter and a phase-shifted full bridge. The interleaved boost converter was chosen to lower the current stresses for the components and to reduce the required input and output capacitance due to the ripple current cancellation in the in- and output. The full bridge is chosen for its galvanic isolation and to perform the high step-up via the transformer turns ratio. It is shown that the maximum intermediate voltage level in between both converters can be derived from the continuous conduction mode of operation. Simulations are provided that show the correct operation of the overall structure. An experimental prototype has been built to demonstrate the overall performance of the converter.
First, several challenging aspects for BIPV converters such as long lifetime, high compactness, high gain and a wide operating range have been discussed. Then a converter design was proposed and the components were selected. The control strategy of the converter is partly closed-loop, partly open-loop. The interleaved Boost converter stage, which will take care of the MPPT and works always under CCM is controlled in closed loop. The second stage, a phase-shifted full bridge, can work under both CCM or DCM. The control of this stage is purely open loop and it has been shown that the voltage stresses can be derived from CCM, as the voltage stress under DCM will always be lower. Finally, PCB prototypes of the Boost and the full bridge converter were developed. The Boost converter works as expected and achieves good efficiencies. However, the full bridge secondary has to deal with oscillatory behaviour and as a consequence, it was not possible to measure the efficiency curve as it was not possible to use the converter under nominal operating conditions. Further research is needed to come up with a good solution for this problem.