1. The main purpose of power flow control in HVDC systems is to:
(A) Regulate active and reactive power between AC grids
(B) Reduce AC line losses only
(C) Store energy only
(D) Correct voltage sags only
2. In HVDC systems, power flow direction can be reversed by:
(A) Changing the firing angle of the converter
(B) Switching off the DC line
(C) Disconnecting the AC grid
(D) Changing the AC frequency only
3. LCC-HVDC power flow control is primarily achieved by:
(A) Controlling the firing angle of thyristors
(B) Adjusting IGBT switching frequency
(C) Using battery storage
(D) Adjusting DC line capacitance
4. VSC-HVDC power flow control is achieved by:
(A) Modulating the phase angle and amplitude of AC voltage at the converter
(B) Adjusting firing angle of thyristors
(C) Changing DC line inductance
(D) Using series capacitors only
5. Active power in HVDC systems is primarily controlled by:
(A) DC voltage or current at the converter
(B) AC frequency only
(C) Load power factor only
(D) Transformer tap changes only
6. Reactive power in VSC-HVDC is controlled by:
(A) AC voltage magnitude at the converter
(B) DC voltage only
(C) DC line resistance
(D) AC line impedance only
7. DC voltage control in LCC-HVDC regulates:
(A) Active power flow and maintains system stability
(B) Reactive power only
(C) Harmonics only
(D) Line frequency only
8. Power modulation in HVDC allows:
(A) Fast response to system disturbances
(B) Only long-term voltage regulation
(C) Only reactive power correction
(D) Frequency control only
9. Constant-current control mode in LCC-HVDC:
(A) Maintains fixed DC current independent of DC voltage
(B) Maintains constant AC voltage
(C) Maintains AC frequency only
(D) Maintains DC voltage only
10. Constant-voltage control mode in VSC-HVDC:
(A) Maintains DC voltage and controls active power flow
(B) Maintains DC current only
(C) Controls AC line impedance only
(D) Maintains AC frequency only
11. Power flow in bipolar HVDC can be:
(A) Split between two poles, with possible reversal on either pole
(B) Only in one direction
(C) Only through monopolar mode
(D) Uncontrollable
12. HVDC power flow control improves:
(A) System stability and allows precise load sharing
(B) Only frequency stability
(C) Only voltage regulation
(D) Only reactive power compensation
13. Converter control in HVDC can provide:
(A) Fast regulation of active and reactive power independently
(B) Only AC voltage control
(C) Only DC line voltage control
(D) Only harmonic mitigation
14. Droop control in HVDC systems is used for:
(A) Load sharing between multiple converters
(B) Voltage regulation only
(C) Harmonic suppression only
(D) Frequency control only
15. DC voltage in LCC-HVDC is controlled by:
(A) Adjusting the rectifier firing angle
(B) Changing AC voltage only
(C) Adjusting AC transformer taps only
(D) Series capacitor banks only
16. Current control in HVDC is mainly applied in:
(A) LCC systems
(B) VSC systems only
(C) AC lines only
(D) Substation transformers only
17. VSC-HVDC converters can operate in:
(A) Four-quadrant mode controlling both active and reactive power
(B) Only active power mode
(C) Only DC voltage mode
(D) AC frequency mode only
18. Power flow control in HVDC allows:
(A) Interconnection of asynchronous AC networks
(B) Only synchronous AC networks
(C) Only low-voltage networks
(D) Residential distribution only
19. Dynamic control of HVDC helps to:
(A) Mitigate transient disturbances and improve system damping
(B) Only reduce line losses
(C) Only correct AC voltage
(D) Only reactive power compensation
20. Power reversal in HVDC is achieved by:
(A) Changing rectifier or inverter operation
(B) Switching DC lines
(C) Disconnecting AC systems
(D) Adjusting frequency only
21. VSC-HVDC provides independent reactive power control by:
(A) Controlling the AC voltage magnitude at the converter
(B) Adjusting DC voltage only
(C) Changing DC line resistance
(D) Using series reactors only
22. Active power in VSC-HVDC can be controlled by:
(A) Modifying the phase angle between AC voltage and converter voltage
(B) Changing AC transformer rating
(C) Adjusting DC line capacitance only
(D) Load shedding only
23. LCC-HVDC rectifier firing angle affects:
(A) DC voltage and power flow
(B) AC voltage only
(C) DC line resistance only
(D) AC frequency only
24. VSC-HVDC modulation allows:
(A) Smooth DC and AC voltage waveforms
(B) Only DC voltage control
(C) Only AC frequency control
(D) Only harmonic filtering
25. HVDC power flow control contributes to:
(A) Congestion management and optimal power dispatch
(B) Only voltage sag mitigation
(C) Only reactive power compensation
(D) Frequency reduction only
26. Load sharing between multiple HVDC links can be achieved by:
(A) Droop control or coordinated control strategies
(B) Changing DC line resistance only
(C) Using AC transformers only
(D) Frequency control only
27. Fast active power modulation in HVDC helps to:
(A) Dampen power oscillations in AC networks
(B) Reduce DC line resistance
(C) Correct only voltage
(D) Control only harmonics
28. Reactive power support by HVDC converters stabilizes:
(A) AC voltage at the point of connection
(B) DC line voltage only
(C) DC current only
(D) AC frequency only
29. Coordinated control of multiple HVDC links ensures:
(A) Optimal system operation and stability
(B) Only reactive power support
(C) Only DC voltage control
(D) Only harmonic mitigation
30. The main goal of power flow and control in HVDC systems is to:
(A) Efficiently transmit bulk power, regulate active/reactive power, and improve system stability
(B) Reduce AC frequency only
(C) Supply residential loads only
(D) Correct power factor only