RESEARCH ON CONTROL STRATEGY OF MODULE CASCADED SST BASED ON DC MICRO-GRID

Bao-Ge Zhang ； Lan-Min Xu ； Long Zhan

《電機工程學刊》 25卷5期 (2018/10) Pp. 193-204

https://doi.org/10.6329/CIEE.201810_25(5).0004

摘要

The Solid-State Transformer (SST) is an important element in the DC micro-grid systems as its outstanding adventures compared with conventional power transformer. It consists of three stages: input stage, isolation stage and output stage. In the topological structure, the modular cascaded converters are used as a grid-connected converter to control the voltage flexibility. To cope with this problem, an adaptive tracking with inner loop and PI voltage outer-loop control strategy of dual-closed-loop is proposed, and in the condition of the L_2 -gain interference suppression theorem is used to achieve it. Such as parametric uncertainties generated by switching devices equivalent resistance, inductive resistance and frequency of the input stage system rectifier. The control strategy of output voltage following the input voltage is adopted for the isolation stage system, which is balanced the voltage and power of the module and reduce the voltage stress of the semiconductor switches device. In the output stage system, a control strategy based on the combination of voltage differential feed-forward and multi-resonance quasi PR control is proposed, which is solved the resonance problem of the LCL grid-connected inverter, and effectively reduces the grid current harmonic problems, while the dynamic and steady-state performance of the system and a substantial increase in anti-jamming capability, and the strategy of three-phase capacitor can be omitted, cost savings. Finally, the validity and effective of the proposed method are verified by simulation and experiment.

關鍵字

Module cascaded ； SST ； adaptive tracking control ； voltage balance ； grid current