Power management of Solid State Transformer in microgrids

By integrating distributed sources and various loads, the microgrid system that is regarded as an intelligent power system with self controlling, protecting and managing functions, has been quickly developing in recent years. Considering that the output power of most distributed sources such as photovoltaic or wind energy are not stable, the control methods for microgrids must be appropriately designed in order to guarantee highquality of the output power and the system stability. Solid State Transformer (SST) is one of the fundamental components for the future microgrids which can totally replace conversional transformers. Its main functions are realized through high frequency power electric converters and control strategies. It may achieve all functions of traditional transformer such as voltage transform, current isolation, power transmission, besides, it can regulate the input current, power factor and enhance output voltage flexibly by providing ideal sine wave. The combination of Microgrid and SST may greatly improve the efficiency and stability of power system. In this paper, both single-phase and 3-phase SST topology are discussed and the simulation models are built on PSCAD. The control techniques are well designed and implemented. The characteristics of SST are explored and verified by key operating results of SST under different conditions.