This set of FACTS Multiple Choice Questions & Answers (MCQs) focuses on “FACTS Controllers”.

1. Which FACT controller does the following figure indicate?

a) Series connected controllers
b) Shunt connected controllers
c) Combined series-series controllers
d) Combined shunt-series controllers

Explanation: FACTS controllers can be classified into four types. They are Series connected controllers, Shunt connected controllers, Combined series-series controllers and Combined shunt-series controllers. A Series connected controller is shown in the given figure.

2. Which of the following is the characteristic of voltage sourced converter?
a) Unidirectional current
b) Unidirectional voltage
c) Unidirectional power
d) Bidirectional voltage

Explanation: Practically speaking, voltage sourced converters are based on thyristors with gate turn-off capability. Here the power reversal is achieved through reversal of current keeping unidirectional-voltage. They are preferred in FACTS Controllers, compared to current-sourced ones.

3. Which of the following is the characteristic of current sourced converter?
a) Unidirectional current
b) Unidirectional voltage
c) Unidirectional power
d) Bidirectional current

Explanation: Actually current-sourced converters may be based on thyristors with no gate turn-off capability. They exhibit the reversal of power flow with reversal of voltage only, keeping unidirectional current. They are more economical for large HVDC schemes, compared to voltage-sourced ones.

4. Combined series and shunt controllers can control ________
a) only voltage
b) only active power flow
c) only reactive power flow
d) voltage, active and reactive power flow

Explanation: Combined series and shunt controllers can control voltage, active power flow, and reactive power flow. The underlying reason is that they encapsulate the characteristics of both shunt and series controllers. They are employed as FACTS controllers as per requirement.

5. All shunt-connected FACTS controllers are variable impedance type controllers.
a) True
b) False

Explanation: All shunt-connected FACTS controllers are NOT variable impedance type controllers. They can be variable impedance type controllers or voltage source type controllers. STATCOM and SVC are both shunt connected but the former is a VSC while the latter is a VIT FACTS controller.

6. All series-connected FACTS controllers are variable impedance type controllers.
a) True
b) False

Explanation: All series-connected FACTS controllers are NOT variable impedance type controllers. They can be variable impedance type controllers or voltage source type controllers. SSSC and TCSC are both series-connected but the former is a VSC while the latter is a VIT FACTS controller.

7. FACTS controllers are based on thyristors with no gate–turn–on capability.
a) True
b) False

Explanation: FACTS controllers may be based on thyristors. Gate turn on capability of a thyristor employed in a FACTS device must be present to make the thyristors work for their intended purposes. However, FACTS controllers may be based on thyristors with no gate –turn–off capability or with gate-turn–off capability, as per requirement.

8. FACTS controllers without gate –turn–off capability are divided as current-sourced and voltage sourced converters.
a) True
b) False

Explanation: Principally FACTS controllers based on thyristors with gate–turn–off capability are divided as current-sourced and voltage sourced converters. Both find applications as per their respective suitability. Compared to current-sourced converters, voltage-sourced are are preferred in FACTS Controllers.

9. In the voltage/current-sourced FACTS controller, the ac input current/voltage varies in magnitude and also in any phase relationship to the system current/voltage.
a) voltage, voltage, voltage
b) voltage, current, voltage
c) current, current, current
d) voltage, voltage, current

Explanation: In the voltage-sourced FACTS controller, the ac input voltage varies in magnitude and also in any phase relationship to the system current. Whereas, in the current-sourced FACTS controller, the ac input current varies in magnitude and also in any phase relationship to the system voltage. From overall economic point of view, the voltage-sourced converters seem to be preferred in FACTS technology.

10. What does VIT stand for?
a) variable impedance type
b) variable impedance thyristor
c) variable inductance type
d) variable impedance transistor

Explanation: The abbreviation VIT stands for variable impedance type. VIT denotes a type of FACTS controllers depending upon the power electronic components incorporated in such FACTS controllers. Static VAR compensator is an example of VSC FACTS controller.

11. VSC is the abbreviation of ________
a) Variable Source Connector
b) Variable Source Converter
c) Variable Synchronous Converter
d) Volatile Source Converter

Explanation: VSC is the abbreviation of variable source converter. VSC denotes a type of FACTS controllers depending upon the power electronic components incorporated in such FACTS controllers. Static synchronous series compensator is an example of VSC FACTS controller.

12. A shunt FACTS controller incorporates its injected current at an angle of ________ with respect to the line voltage, to handle reactive power in a transmission system.
a) 0°
b) 90°
c) 45°
d) 180°

Explanation: A shunt FACTS controller incorporates its injected current at an angle of 90° with respect to the line voltage, to handle reactive power in a transmission system. To lever real power in a transmission system, a shunt FACTS controller requires any angle other than quadrature (90°) relationship between its current and the line voltage.

13. What does a series FACTS controller inject to handle reactive power in a transmission system?
a) Current at 0°
b) Current at 90°
c) Voltage at 0°
d) Voltage at 90°

Explanation: A series FACTS controller injects voltage at an angle of 90° with respect to the line current, to handle reactive power in a transmission system. To lever real power in a transmission system, a series FACTS controller requires any angle other than quadrature (90°) relationship between its injected voltage and the line current.

14. Which among the following is the most dominant converter employed in FACTS Controllers?
a) Voltage-sourced converters
b) Current-sourced converters
c) Both current-and voltage-sourced converters
d) Power sourced converters

Explanation: Practically speaking, the most dominant converters that are employed in FACTS Controllers are the voltage sourced ones. Their operations are based on thyristors with gate turn-off capability where the power reversal exhibits reversal of current keeping unidirectional-voltage. On the other hand current-sourced converters having thyristors with no gate turn-off capability are more economical for large HVDC schemes. In them the reversal of power flow can be achieved with reversal of voltage only keeping unidirectional current.

15. How are FACTS controllers?
a) Fast acting
b) Slow acting
c) Unresponsive
d) Hypothetical

Explanation: FACTS controllers are fast acting power electronic ones. They along with conventional power system devices are responsible to enhance power transfer capability of the flexible ac transmission system. Power electronic controllers are fast acting by their own characteristic feature inherent to the power electronic components inside.

Sanfoundry Global Education & Learning Series – Flexible AC Transmission System (FACTS).

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