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The purpose of this invention is to provide an alternative to traditional grid-connected converter systems that is safer and more flexible, efficient, and cost-effective. Voltage source inverters used in these systems are typically buck-type, which always operate with an AC voltage lower than their DC voltage. Consequently, the inverter’s minimum DC voltage must be higher than peak grid voltage. This high DC voltage threshold leaves the system susceptible to dangerous DC arc faults, and requires PV strings to have a minimum number of panels to prevent dropping below grid voltage in the event of shading.
This invention utilizes a transformer-less system whereby a traditional voltage source inverter is coupled via a single inductor to an AC/AC converter, which is used to interface between the inverter and the AC voltage source. This eliminates the minimum DC voltage requirement, allowing any number of panels to be used in a PV string and removing the concern for DC arc faults. In addition, the use of a single inductor removes the need for bulky and expensive transformers. These same benefits apply to battery DC sources, and also allow for the independent charge/discharge of each battery through its own DC/AC inverter.