Flexible AC Transmission Systems

The growing number of small, decentralized power plants such as solar, wind, and biogas plants is making it much more difficult for grid operators to ensure reliable and stable grid operation. Flexible AC Transmission Systems (FACTS) are the perfect solution for increasing the reliability of AC grids, improving power quality, and boosting transmission efficiency. Siemens Gas and Power supports customers around the world with innovative FACTS to help them master the challenges of energy transitions.

Series Compensation (SC)

Increased stability by series compensation

Series compensation makes use of capacitors, reactors or power electronic devices offering high flexibility. Series Compensators (SC) provide an increase in transmission system stability and capacity for power transmission.

Typical applications of SC are Fixed Series Capacitors (FSC), Thyristor Controlled Series Capacitors (TCSC) and Thyristor Protected Series Capacitors (TPSC).

Static Var Compensator (SVC)

Dynamically stabilizing network and busbar voltage

Nowadays, power producers and providers throughout the world are faced with greater demands for bulk power flow, lower-cost power delivery, and higher reliability, while industrial consumers have to adhere to stringent power quality requirements. The SVC is a shunt connected device injecting dynamically inductive or capacitive reactive power into the transmission grid.

The main task is voltage stability and reactive power control of transmission systems and system nodes or industrial power distributions. An SVC (Static Var Compensator) is a high voltage system that stabilizes the network voltage dynamically at its coupling point, to keep the network voltage constant at a set reference value. 


Compact solution for increased grid stability

Power producers and system operators are faced with increasing demands for bulk power transmission, low-cost power delivery, and high system reliability. At the same time, bottlenecks cause limitations in power transmission. For highly dynamic load compensation in the industry a very fast compensation system is called for. 

The innovative SVC PLUS for Reactive Power Compensation is a cost efficient, space saving, flexible solution to increase dynamic stability and power quality of the grid, based on multilevel Voltage-Source Converter (VSC) technology.

SVC PLUS Frequency Stabilizer

Frequency and voltage support for dynamic grid stability

As the infeed of power from renewable sources continuously replaces conventional synchronous power generation, the grid frequency is getting more sensitive due to the reduced amount of rotating machines. Now grid operators are faced with the challenge to provide sufficient system inertia of synchronous generators with high rotating masses to stabilize the grid.

An SVC PLUS Frequency Stabilizer can solve this challenge as it is able to emulating system inertia by boosting high active power into the grid when needed. In addition it offers voltage support by means of reactive power compensation.

Synchronous Condenser

Essential to provide grid stability e.g. at high shares of wind and solar power infeed

The addition of renewables-based power generation to the energy mix, phase-out of thermal power plants, new HVDC systems, and the extension of power supply systems to remote areas influence the stability of transmission networks. 

Synchronous condensers offer grid stability e.g. for transmission systems with a high amount of renewable infeed by providing short-circuit power, inertia and reactive power compensation.

Mechanically Switched Capacitors / Filter Circuits

Stable power grids for industries and utilities

Mechanically switched devices (MSC/MSCDN) are the most economical reactive power compensation devices. MSCs are a robust solution for voltage control and network stabilization under steady state conditions. The MSCDN additionally offers a damping network to avoid resonance conditions in the electrical system. 

And in industrial plants with rising amounts of converter fed drives and other nonlinear consumers the need for efficient reduction of harmonic voltages along with power factor improvement becomes increasingly important – tuned filter circuits are a remedy.

Trade press article

Improving grid operator economics with power electronics

In deregulated energy markets, grid operators are looking to use market structures to address grid stability issues emerging from the clean energy transition. As a result, the ability to provide reactive power compensation with STATCOM technology could open up new revenue streams.

FACTS at a glance

Grid stability and power quality made to measure

While every power grid has specific challenges in terms of power quality, reactive power compensation, and grid stability, our FACTS systems offer customized solutions to these challenges from a single source for utility and industrial applications.

Modular FACTS devices to suit all demands

Flexible AC transmission systems (FACTS) are a family of power transmission solutions that contribute to enhanced grid stability and power quality. Its specialized devices offer either parallel or series compensation.

While series compensation is primarily used to increase the power transfer capability on transmission lines, Siemens devices for parallel compensation influence the network voltage at their point of common coupling by actively injecting or absorbing reactive power. Parallel-connected synchronous condensers stabilize the network by providing short circuit power and inertia. With these solutions installed in the system, unacceptably high voltage fluctuations and power failures can be prevented, network assets can be optimally utilized, and load-induced disturbances can be mitigated.

Benefits and tasks of FACTS systems


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