Unified power flow controller (UPFC PLUS®)

Stabilize AC grids in milliseconds and get the most out of existing infrastructure: Increasingly decentralized energy systems and the associated uncontrolled power flows pose new challenges for the existing, mature grid infrastructure. Thermal overloads in the lines and a growing number of cases in which frequency and voltage come critically close to acceptable range limits, or even exceed them, threaten grid stability and the transmission infrastructure, and often require costly redispatch intervention to deal with current and voltage factors. Compared to traditional power flow controllers, UPFC PLUS® controls power flow in just milliseconds. The unified power flow controller UPFC PLUS® thus stabilizes the AC grid even when critical situations develop suddenly (Grid Code N-1). That means UPFC PLUS® lets you get the most from your existing grid capacity while maintaining maximum protection, reducing the risk of power failures, and minimizing redispatch costs.      

Even when sudden faults occur, UPFC PLUS® stabilizes the AC grid, offering highly efficient support for Grid Code N-1 situations affecting the existing grid infrastructure. Its modular multilevel converter (MMC) technology enables a sufficiently rapid response time of just a few milliseconds in order to prevent power failures.

The UPFC PLUS® solution is based on the modular multilevel converter (MMC) architecture from voltage source converters (VSC) in semiconductor technology, as developed by Siemens Energy and already proven in SVC PLUS® and HVDC PLUS®.

A unified power flow controller is used to control and influence the electrical energy transmitted through individual lines in intermeshed, supra-regional power networks. UPFC PLUS® can therefore be used to meet specific, contractually agreed power throughputs in intermeshed grids.

The scope of application is aimed at high-voltage electricity transmission networks using three-phase AC at voltage ranges of 220 kV to 500 kV, and its control functions make use of power electronics similar to the systems used in HVDC transmission. Unlike HVDC, the power electronics are not used directly for power transmission but to influence and modulate the AC current being transmitted. In power electronics, UPFC is an example of a flexible AC transmission system (FACTS).