The synchronous voltage source is implemented by a multi-pulse inverter using gate turnoff (GTO) thyristors . It is capable of generating internally the reactive power necessary for network compensation, and is also able to interface with an appropriate energy storage device to negotiate real power exchange with the ac system. The paper develops a of power flow control using solid - state synchronous voltage sources for shunt compensation, series compensation , and phase angle control .

It also describes the unified powerflow controller that is able to control concurrently or selectively all three network parameters(voltage, impedance, angle) determining power transmission. compensation method of employing thyristor switched capacitors and reactors shows its superior performance, uniform applicability, smaller physical size, and lower overall cost. There are clear indications that solid-state synchronous voltage sources represent the next technology for ac transmission system compensation and power flow control.

This technology offers operating features, functional performance, and application flexibility unattainable by the presently used circuit arrangements. The synchronous voltage source can be considered an ideal 60 Hz generator that has no inertia and produces an almost sinusoidal output voltage with independently variable amplitude and phase angle, thus facilitating rapid, decoupled controls for reactive and real power exchange. It can be used uniformly to control transmission line voltage, impedance, and angle by providing reactive shunt compensation, series compensation, and phase-shifting.