Topology-Morphing Photovoltaic Microconverter With Wide MPPT Voltage Window and Post-Fault Operation Capability

Abstract

In this paper the concept of wide input voltage range photovoltaic microconverter with postfault operation capability is presented. This microconverter could remain operational in the case of short-or open-circuit failure of any switch of its front-end inverter. When the fault occurs, the control system automatically identifies the fault and applies the special post-fault modulation sequence thus keeping the functionality of the microconverter unchanged. The research findings are validated by the help of a 350 W experimental prototype specially developed for integration of silicon PV modules into the residential DC nanogrids with the nominal voltage of 350 V. Paper explains the multi-mode operation principle and fault identification routine. It presents the experimental efficiencies and evaluates the maximum power point tracking performance of the microconverter prior and after the short-circuit fault of an upper switch of the inverter. The daily energy yield test conducted for both cases has confirmed that the proposed approach can extend the service life of PV microconverters with a moderate impact on their performance. INDEX TERMS DC-DC power converters, digital control, fault diagnosis, fault tolerance, fault-tolerant control, photovoltaic systems, power electronics, pulse width modulation, quasi-Z-source converters.

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