212 / 2019-07-05 19:24:30

Optimizing Voltage Balancing Method of Power Electronic Transformer Based on MMC

modular multilevel converter, voltage balancing sorting algorithm, the reordering factor , switching losses

In practical engineering applications, capacitor voltage sorting of Modular Multievel Converter (MMC) in Power Electronic Transformer (PET) input stage is a huge engineering difficulty. To solve the problems of traditional voltage balancing sorting algorithm, such as high switching frequency, large amount of computation and large switching loss, an optimizing voltage balancing method is proposed to reduce time complexity and switching frequency. Firstly, merging sorting algorithm is used to select the appropriate figures as reference values of the randomized-select algorithm, and then the randomized-select algorithm is used for quick sorting. On this basis, the reordering factor is introduced. When capacitance voltages experiences small change, it avoids reordering and keeps the trigger pulse unchanged; on the contrary, quick sorting method is adopted. Selective sorting of MMC controllers not only further reduces the computational complexity of the controllers, but also effectively reduces switching losses. Finally, the feasibility and validity of the proposed optimization method are verified by Matlab simulation.