Controlling Power Flows in T&D Systems using Power Electronic Converters

The key to the provision of reliable and stable electricity supplies is the control of the real and reactive power flows in the network. A range of well proven power electronic converters are available which can provide automatic control, either for long distance bulk power transfers or for the integration of distributed generation into the network. The presentation will describe two families of converters. Series connected devices, such as High Voltage Direct Current (HVDC) and Thyristor Controlled Series Capacitor (TCSC), and Shunt connected devices, such as Static Var Compensator (SVC), Re-locatable SVC (RSVC), Static Synchronous Compensator (STATCOM) and Distribution STATCOM (D - STATCOM). These are the most widely used power electronic controllers. However, other devices are also emerging as new semiconductor devices, such as high power transistors, provide additional functionality, which can enhance the capabilities offered by these converters. These devices, still at the demonstrator stage, will be mentioned briefly. In rapidly evolving transmission and distribution systems, the need for automatic control of real and reactive power flow will become of paramount importance, if the network operators are to deliver reliable power supplies to their customers.