Research on Parallel Multi-pulse Rectification Technology for Zigzag Power Electronic Transformers Based on Volume Optimization

To solve the problem of conventional phase shift transformers that limit the scope of application due to their size, the power electronic transformer is combined with multi-pulse rectification to reduce the number of core and coil turns in the transformer through frequency step-up, thereby reducing the size of the transformer. To optimize the structural problems of unbalanced magnetic circuit and asymmetric star-angle coupling structure of traditional phase shifting transformer with three core columns, a zigzag structure is used to provide channels for zero-sequence flux, thus reducing the zero-sequence current in the circuit and solving the problem of unbalanced current distribution between diode bridges. The AC-AC operating principle of user plane entity(UPE) is analyzed, the topology of zigzag phase shift transformer and the operating mode of rectifier bridge are studied, the mathematical expressions of input current and load voltage of the system are derived, and the magnetic circuit of the transformer is analyzed and the core is optimized. The simulation model is built by Simulink, which improves the symmetry of the input current compared with the conventional power electronic phase shift transformer system, and the correctness of the theoretical analysis is verified by the simulation and experimental results.