Multilevel Inverter with a New Modulation Method Applied to Solid-State Transformer in PV Applications

According to recent improvements in microgrid and Renewable Energy Sources (RESs), it is vital to use an alternative system for conventional transformers due to its lack of controllability and having high volume and weight. So, the senses gathered to the Solid-State Transformer (SST) because of its relevant advantages. A power electronic converter converts a low-frequency ac voltage waveform to a medium frequency voltage with variable amplitude in most SST structures. First, there is a need to convert the DC voltage to a pure sinusoidal one for using the High Voltage DC (HVDC) in Distributed Generator (DG) sources such as Photovoltaic (PV) farms and microgrids. Then an ac-ac converter is used to produce a medium frequency waveform. These structures need two stages of energy conversions. This paper proposes a new configuration with a specific modulation method to convert the DC voltage waveform directly to a medium frequency voltage waveform with variable maximum amplitude. The simplicity of the control system, reduced volume, and weight, as well as the reduced number of energy conversion stages are the advantages of the proposed system.