The architecture and control of large power networks with distributed generation

This paper briefly summarises the evolution of transmission and distribution networks since the late 19th century, and explains that the introduction of significant amounts of distributed generation may bring about a future fundamental change to the network architecture. Providing a secure power network is a demanding task, but as network complexity is expected to grow with the connection of large amounts of distributed generation, so the problem of integration, not just connection, of each successive generator becomes more protracted. A fundamental change to the network architecture may eventually become necessary and a new architecture, perhaps based on power cells, containing generation, energy storage and loads has been proposed by some researchers. This paper describes a novel power cell interface. It makes the case for the conventional power transformer to be replaced by an Active Transformer, the objective being to provide a more controllable, flexible and robust connection that will facilitate greater network management and business opportunities, and new power flow control features. The Active Transformer design is based on an a.c. link system described by Thomas Lipo in 1986 and an a.c.-a.c. high-frequency direct converter design demonstrated by Dang in 2006. It consists of a resonant, supply-side converter, a high frequency transformer and a resonant, load-side converter. This paper describes a model of the Active Transformer, built in Simulink®, and presents the results of simulations that demonstrate its action to control current in a resistive load.