Implementation and control of a bidirectional high-gain transformer-less standalone inverter

This paper describes a bidirectional inverter topology for standalone applications. The topology, consisting of a Quadratic Boost Converter based Voltage Source Inverter (VSI), can achieve high conversion ratio both in inverter as well as rectifier operations without the use of a transformer. In addition, the same architecture can also be used to realize DC-DC conversion (both Step-Up and Step-Down). This improves the adaptability of the topology in renewable system realization, especially in rural areas, and makes it suitable to handle variable input sources. The bidirectional power transfer capability with high conversion ratio is demonstrated using a lab prototype. The controller design for the topology operating as a standalone inverter is described in a step-by-step manner and this has been implemented using TMS320F28335 DSP. The output voltage regulation capability, when the high-gain inverter is subjected to load-step changes as well as variable input, has been validated using experimental results.