Grid-Current Control of a Differential Boost Inverter With Hidden LCL Filters

Single-phase differential boost inverter, built from two identical dc-dc boost converters, has been suggested as an alternative to the usual connection of a dc-dc boost converter to a standard full-bridge inverter. Some control schemes for controlling it have also been proposed, but mostly for voltage regulation, supplying a standalone load, rather than grid-current control. Moreover, it has never been identified that two LCL filters are hidden in the differential boost topology. Problems related to their associated resonances have therefore not been discussed, especially their variations with duty ratios. It is thus necessary here to unmask the hidden LCL filters, which upon clarification, permits vast knowledge from grid-current control of a standard LCL -filtered inverter to be extended for differential inverter control. However, the extension involves many challenges introduced by the varying resonance frequencies, nonlinearity, and many control options permitted by the differential boost inverter. These challenges are addressed now with simulation and experimental results provided for verifying direct grid-current regulation of a differential boost inverter.