Flexible AC Transmission Systems

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).

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. 

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.

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.

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 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.

Decentralized energy systems and the associated uncontrolled power flows pose new challenges for the existing AC grids. 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. The Unified Power Flow Controller (UPFC PLUS) controls power flow in just milliseconds thus stabilizes the AC grid even in critical situations (Grid Code N-1). 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.