Study on the optimal DC voltage control for power electronic transformer

Power electronic transformer (PET), the key equipment for future smart grid, is vital for the whole power grid to be in normal operation. The mathematical relationship between the DC-link voltage and the system parameters for PET were analyzed in this paper. Based on the analysis, the optimal DC-link voltage for PET is obtained by mathematical deduction. Then, a novel adaptive voltage regulation method is proposed, in which the DC-link voltage reference value will be maintained in the required optimal voltage level, and it also can be adaptively changed according to different grid voltage levels and load levels. Therefore, PET can avoid the grid voltage and load level fluctuation impact on the input current distortion and output voltage stability. Finally, representative simulation results in PSCAD/EMTDC verify the validity and effectiveness of the optimal DC-link voltage design and the proposed adaptive voltage regulation method.