SuperVAR® Dynamic Synchronous Condensers

Utilities today face an ever-growing demand for higher quality, reliable power and increased transmission capacity. The key to increasing reliability and capacity is ensuring that grid voltage is properly regulated. This helps prevent service disruptions, damage to electrical service equipment, generating plants and other components of the AC power grid and can help maximize transmission capacity. Utilities keep voltage levels stable by maintaining a balance of real power (watts) and reactive power (VARs) on their transmission grids.

American Superconductor's SuperVAR machines are rotating machines, much like motors and generators, and utilize high temperature superconductor technology and serve as reactive power "shock absorbers" for the grid, dynamically generating or absorbing reactive power (VARs), depending on the voltage level of the transmission system.

AMSC's SuperVAR  machines use standard synchronous condenser frames and stator coils mated with new, power-dense rotor coils made from AMSC's HTS wire. The result is a synchronous condenser that is more efficient than conventional machines - without the typically high rotor maintenance costs. SuperVAR machines are specifically designed for continuous, steady-state dynamic VAR support while having multiples of their rated output in reserve for transient problems. The HTS rotor enables these machines to provide up to eight times their rated capacity for short periods. AMSC expects to also extend the product line to include units of substantially larger ratings.

Benefits

• Transient dynamic voltage support and stability (leading and lagging VARs) at a multiple of the
  machines rating

• Economic transmission voltage support and stability improvement

• Increased transmission capacity by reducing transmission losses

• Power factor correction during steady state operation

• Stable operation up to its rated load in either leading or lagging mode

• Minimizes operating power consumption

• Minimizes harmonic content

• Requires less maintenance on machine rotor windings

• Modular transportable design

• Easy installation

VARs and Reactive Power

Voltage is the "pressure" that drives electrical current through power lines. Reactive power, which is measured in VARs (volt-ampere-reactive), is the component of electricity that maintains the proper level of voltage in transmission lines to drive "real power," which is measured in Watts, through the power lines to customers.

Reactive power cannot be stored and must be externally supplied to the power grid.

Synchronous condensers share much of their architecture with electric synchronous motors and generators. Their primary function is to stabilize grid voltage by injecting or absorbing reactive power. Reactive power, which can also be understood as the "out-of-phase" component of AC power, can be either lagging (current lagging voltage, corresponding to inductive reactance) or leading (current leading voltage, corresponding to capacitive reactance).

As power demands increase in any AC system, the need for reactive power generally increases. When the transmission grid is forced to deliver large amounts of reactive power over long distances, it can limit the amount of real power that can be generated and delivered across a transmission grid. Therefore, it is advantageous to produce the necessary reactive power close to the loads.

The HTS Advantage

By utilizing AMSC's HTS wire, SuperVAR  machines provide a more efficient system with significant advantages over conventional synchronous condensers such as lower standby losses, higher output, lower cost and higher reliability. In addition, the HTS rotor design increases the device's over-excitation and under-excitation output limits to its full-rating without loss of critical clearing time following a transient fault. SuperVAR  machines do not experience thermal fatigue of the field coils as the VAR output is varied from no-load to full-load allowing SuperVAR  synchronous condensers to be used for peaking as well as base load applications without worries of loss of life due to frequent load changes. These machines do not introduce harmonics into the grid, but do retain high operating efficiency (losses versus VARs) down to 20% of its rated output.

Demand for electric power continues to grow and utilities are looking for ways to leverage their existing grid assets to meet rising customer demand for more reliable power. SuperVAR  machines enable existing transmission assets to be operated at higher capacities thereby minimizing the need to construct new power generating facilities or install additional transmission lines in areas of increasing demand. SuperVAR machines can also serve as lower cost replacements for old, polluting inner city Reliability-Must-Run (RMR) generating facilities which are required to operate in order to maintain system reliability and voltage support. The innovative design of SuperVAR  synchronous condensers provides a highly efficient alternative to dynamic voltage grid support available from other devices.

Is SuperVAR® or D-VAR® the Right Solution for my Grid?

The SuperVAR machine is a new product that complements AMSC's family of reactive power grid stabilization solutions which includes AMSC's D-VAR (dynamic VAR) systems.

• SuperVAR synchronous condensers are specifically designed for continuous, steady-state dynamic VAR support and they maintain a reserve for transient problems.

• D-VAR systems - which are based on AMSC's PowerModule™ power electronic converters - are designed to solve local voltage issues through a controlled, directed output thus addressing more specific existing or known transient problems.

Transmission and distribution grids are complex systems that can require a combination of steady-state dynamic and transient VAR support to ensure reliable power delivery. AMSC's transmission planning and sales teams have decades of experience in the power industry. AMSC works together with utilities and power system operators and conducts extensive studies in order to deliver optimized transmission grid solutions.