TABLE OF CONTENTS In general, digital control theory is available to be applied in other branches of power electronics such as power factor correction (PFC), static compensation (STATCOM) and flexible AC transmission system (FACTS), reactive power (VAr) compensation, and power quality control (PQC). We will describe digital control theory applying in some branches of power electronics in this chapter.
Reactive power has no real physical meaning, but is recognized as an essential factor in the design and good operation of power systems. Real and reactive power on a transmission line in an integrated network is governed by the line impedance, voltage magnitudes, the angle difference at the line ends, and the role the line plays in maintaining the network stability under dynamic contingencies. Power transfer in most integrated transmission systems is constrained by transient stability, voltage stability and/or power stability. Reactive power (VAr) compensation or control is an essential part in a power system to minimize power transmission losses, to maximize power transmission capability and to maintain the supply voltage.
It is increasingly becoming one of the most economic and effective solutions to both traditional and new problems in power transmission systems. It is a well-established practice to use reactive at a particular bus bar in any electric power system. In the past, synchronous condensers, mechanically switched capacitors and inductors, and saturated reactors have been applied to control the system voltage in this manner. Since the late 1960s, thyristor controlled reactor (TCR) devices together with fixed capacitors (FCs) or thyristor...
