Static Var Compensators (SVCs) are devices that can quickly and reliably control line voltages. An SVC will typically regulate and control the voltage to the required set point under normal steady state and contingency conditions and thereby provide dynamic, fast response reactive power following system contingencies (e.g. network short circuits, line and generator disconnections). In addition, an SVC can also increase transfer capability, reduce losses, mitigate active power oscillations and prevent over voltages at loss of load.
The SVC is customized to fit each customer with their specific needs. The SVC consists of a number of fixed or switched branches, of which at least one branch includes thyristors, and the combination of branches can be varied a lot depending on requirements. An SVC typically includes a combination of at least two of the given items below (e.g. TCR/FC or TCR/TSC/FC):
- Thyristor controlled reactor (TCR)
- Thyristor switched capacitor (TSC)
- Harmonic filter (FC)
- Mechanically switched capacitor bank (MSC) or reactor bank (MSR)
Most common topologies for SVCs are: TCR/FC or TCR/TSC/FC. The main advantage for using a topology with TSC branch(es) is to reduce the losses (by reducing the filter size). Mechanically switched banks can be included both on HV and LV side of SVC transformer to increase the total reactive power support outside the dynamic range. Hitachi ABB Power Grids' SVC control system can be utilized for controlling new or existing external shunt banks.