19-05-2014, 01:03 PM
Automatic Series Compensation Technique Using Thyristor Controlled Series Capacitor (TCSC)
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Abstract
Reactive power compensators are employed worldwide to reduce effect of load disturbances. This project discusses the development of configuration of the Thyristor controlled series capacitor (TCSC). The purpose of this technique is to increase the power transmission capability at optimum level.TCSC is used in power system to dynamically control the reactance of transmission line in order to provide sufficient load compensation. This technique has maximum availability, minimum transmission losses, and minimum environmental impact.We have minimized the value of current and reactive power within limit at distribution site .Thus current has reduced leading to reduction in IR voltage drop and I2R losses. Also the reactive power consumption has reduced indicating improvement in power factor.
Introduction
To compensate the reactive power which is consuming by load on receiving end of transmission line we use TCSC. Thyristor-controlled series capacitors (TCSC) can provide many benefits for a power system including controlling the power flow on the line, damping power oscillations & mitigating sub synchronous resonance. In order to assess the benefits and potential interactions of TCSC on a utility system and to determine its appropriate control settings, accurate models of TCSC are needed.One of the major attractive features of TCSC is the ability to mitigate SSR. However, in order to investigate sub synchronous torsional interaction between the TCSC and turbine-generator shafts, and to evaluate control interactions between TCSC and other devices in the power system such as SVC and excitation systems, an analytical model of a TCSC is needed which permits the linearization of the system dynamics . The analytical model should be accurate in the frequency range between 0 Hz and twice the operating frequency in order to accurately predict interactions in this frequency range.
B. The TCSC Controller:
The basic conceptual TCSC module comprises a series capacitor, C, in parallel with a thyristor-controlled reactor, LS as shown in Fig 1. However, a practical TCSC module also includes protective equipment normally installed with series capacitors, as shown in Fig. 2. A metal-oxide varistor (MOV), essentially a nonlinear resistor, is connected across the series capacitor to prevent the occurrence of high-capacitor over-voltages.
Not only does the MOV limit the voltage across the capacitor, but it allows the capacitor to remain in circuit even during fault conditions and helps improve the transient stability. Also installed across the capacitor is a circuit breaker, CB, for controlling its insertion in the line.