VAR Compensation on Load Side using Thyristor Switched Capacitor and Thyristor Controlled Reactor

Generally, AC loads are the inductive loads which are reactive in nature. These loads, thus, demand and draw reactive power from the supply source. If these loads draw large lagging current from the source, this will cause excessive voltage drop in the line, which can even cause the voltage collapsing in the line itself if the drop in the line is excessively high. VAR compensation means efficient management of reactive power locally to improve the performance of AC power systems. In this paper, Static VAR Compensator, using TSC (Thyristor Switched Capacitor) and TCR (Thyristor Controlled Reactor), is designed and simulated in MATLAB to maintain the power factor of power system nearly to unity at all times. TSC and TCR are basically shunt connected capacitors and inductor respectively whose switching (of capacitors) and firing angle control (of inductor) operations are carried out using thyristors. The purpose of capacitors is to supply lagging VAR as per the demand by the connected loads and the overcompensation due to excess VAR generated by the discrete set of turned on capacitors are absorbed by the adjustable inductive reactance of the inductor in TCR branch through firing angle control mechanism.

An R-L Static Var Compensator (SVC)

Traditional static var compensators (SVCs) employ shunt reactors and capacitors. These standard reactive power shunt elements are controlled to produce rapid and variable reactive power. Power electronic devices like the thyristor etc. are used to switch them in or out of the network to which they are connected in response to system conditions. There are two basic types, namely the thyristor-controlled reactor (TCR), and the thyristor-switched capacitor (TSC). In this paper we wish to investigate a compensator where the reactor or capacitor is replaced by a series connected resistor and reactor (R-L). The performance equations are derived and applied to produce the compensator characteristics for each of the configurations. Their performances are compared, and the contrasts between them displayed. All three configurations are made to achieve unity power factor in a system.

Asymmetric Compensation of Reactive Power Using Thyristor-Controlled Reactors

The thyristor-controlled reactor (TCR) compensator for smooth asymmetric compensation of reactive power in a low-voltage utility grid is proposed in this work. Two different topologies of compensator were investigated: topology based on a single-cored three-phase reactor and topology with separate reactors for every phase. The investigation of the proposed TCR compensator was performed experimentally using a developed experimental test bench for 12 kVAr total reactive power. The obtained results show that employment of separate reactors for every phase allows us to control the reactive power in every phase independently, and that the TCR compensator with three single-phase reactors is suitable for smooth and asymmetric compensation of reactive power in a low-voltage utility grid.