The UPFC has numerous conceivable working modes. Specifically, the shunt inverter is working in such an approach to infuse a controllable current, Ish into the transmission line. The shunt inverter can be controlled in two distinct modes:

1) VAR CONTROL MODE:

The reference information is an inductive or capacitive VAR ask. The shunt inverter control makes an interpretation of the VAR reference into a comparing shunt current demand and changes gating of the inverter to build up the coveted current. For this method of control a criticism signal speaking to the dc transport voltage, Vdc, is additionally required.

2) AUTOMATIC VOLTAGE CONTROL MODE:

The shunt inverter responsive current is consequently managed to keep up the transmission line voltage at the purpose of association with a reference esteem. For this method of control, voltage criticism signs are acquired from the sending end transport bolstering the shunt coupling transformer.

The arrangement inverter controls the greatness and point of the voltage infused in arrangement with the line to impact the force stream on hold. The genuine estimation of the infused voltage can be acquired in a few ways.

1) DIRECT VOLTAGE INJECTION MODE:

The reference inputs are straightforwardly the size and stage point of the arrangement voltage.

2) PHASE ANGLE SHIFTER EMULATION MODE:

The reference information is stage relocation between the sending end voltage and the less than desirable end voltage.

3) LINE IMPEDANCE EMULATION MODE:

The reference information is an impedance worth to embed in arrangement with the line impedance.

4) AUTOMATIC POWER FLOW CONTROL MODE:

The reference inputs are estimations of P and Q to keep up on the transmission line regardless of framework changes.