Transformer-less UPFC modulation and control

In this study, a modulation and control approach for the novel transformerless unified power flow controller (UPFC) has been presented. It is well known that the standard UPFC, which consists of two back-to-back inverters, needs large and frequently intricate zigzag transformers for isolation and to achieve high power ratings with desirable voltage waveforms. To solve this problem, a completely transformer-free UPFC based on two cascade multilevel inverters has been created. In comparison to older technology, the new UPFC has a number of benefits, including transformerlessness, lightweight, high efficiency, low cost, and quick dynamic response. Here, the emphasis is on modulation and control for this transformerless UPFC, including the best fundamental frequency modulation for low THD and high efficiency, independent active and reactive power management over the transmission line, dc-link voltage balancing control, and more. The new UPFC with the suggested control approach performs as anticipated, according to experiments on a 4160-V test setup. Both steady-state and dynamic-response results will be shown in this work.