Types of static VAR compensators are

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Examoogle · Accepted Answer

Both a and b

Explanation: Static VAR Compensators (SVCs) are shunt-connected FACTS devices that regulate voltage by controlling the reactive power flow. They are typically implemented as hybrid configurations combining fixed capacitors and thyristor-controlled reactors to achieve a smooth range of inductive and capacitive compensation.

Working Principle: The FC-TCR (Fixed Capacitor-Thyristor Controlled Reactor) uses a fixed capacitor bank and a reactor controlled by thyristor firing angles to vary reactive power. The TSC-TCR (Thyristor Switched Capacitor-Thyristor Controlled Reactor) improves efficiency by switching discrete capacitor banks to minimize harmonics and losses while using the TCR for fine continuous control.

Key Formulas: $Q_{TCR}(\alpha) = \frac{V^2}{\omega L} (1 - \frac{2\alpha}{\pi} - \frac{\sin(2\alpha)}{\pi})$ — Reactive power control based on thyristor firing angle $\alpha$; $Q_{net} = Q_C - Q_L(\alpha)$ — Net reactive power balance at the point of common coupling

Key Points: FC-TCR is the most common configuration for industrial and transmission voltage support.; TCRs generate harmonic currents that require filtering, whereas TSCs are stepped and inherently lower in harmonic generation.; SVC response time is typically in the range of 10 to 30 milliseconds.; The firing angle control $\alpha$ allows for continuous variation of the reactor current.

Advantages: Rapid voltage regulation during transient disturbances; Continuous control of reactive power flow; Improved power factor and stability margins

Disadvantages: Generation of harmonic distortion (especially in TCRs); High capital cost compared to mechanical compensation; Requires complex control logic for firing angles

Applications: Voltage stability enhancement in long transmission lines; Flicker compensation for arc furnaces; Dynamic voltage support for industrial loads

Additional Info: FC-TCR is considered the most cost-effective solution for many utility applications.. TSC-TCR is technically superior for reducing overall system losses but significantly more expensive due to multiple thyristor switches.

Answer: C is correct — Both FC-TCR and TSC-TCR are recognized topologies of Static VAR Compensators used in power systems.

Exam Tip: Remember that SVCs are 'shunt' devices. Always distinguish them from 'series' devices like TCSC, which control line impedance rather than bus voltage.

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