Advanced PWM Technique for Performance Improvement of Solid-State Transformer-Based Renewable Energy Systems

The increasing integration of renewable energy sources such as solar and wind energy into modern power grids necessitates advanced power conversion technologies. Solid-state transformers (SSTs) play a critical role in this context, particularly in the low/medium-voltage dc to medium-voltage ac conversion stage. However, the performance of SST is heavily influenced by the employed pulse width modulation (PWM) technique used in switching of the power converter. Conventional PWM methods often lead to significant harmonic distortion and power losses, limiting overall system efficiency and thermal stability. This work presents an advanced trapezoidal-triangular carrier-based PWM technique designed to reduce the total harmonic distortion (THD) and power loss of the cascaded H-bridge (CHB) multilevel inverter (MLI) used in SST. The proposed approach is evaluated through comprehensive simulations in MATLAB/Simulink and PLECS, achieving an unfiltered output voltage THD of 16% and total power loss of 10.76 kW for a 300 kW CHB inverter, both improvements over existing PWM techniques. A scaled-down laboratory prototype is developed and tested to experimentally validate the simulation results. The findings confirm that the proposed PWM strategy effectively enhances the performance of the CHB inverter deployed in the SST, making it a promising solution for efficient and reliable renewable energy integration into the power grid.