EX-702-B HVDC and FACTS - Jun 2025 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aExplain the flow of power in AC parallel paths and meshed systems.
   How to answer

   • Define parallel and meshed AC system configuration
   • Power flow expression P = V1*V2/X * sin(delta)
   • Effect of impedance, angle and voltage on load sharing
   • Problems of uncontrolled flow, loop flows and overloading
2. 7 Marks
   bDiscuss the different types of FACTS controllers with examples.
   How to answer

   • Define FACTS controllers purpose
   • Classification: series, shunt, combined, series-series
   • Examples: SVC, STATCOM, TCSC, SSSC, UPFC, IPFC
   • Brief function of each category
3. 7 Marks
   aExplain the objectives and methods of controllable VAR generation.
   How to answer

   • Objectives: voltage control, power factor, stability
   • Need for controllable VAR
   • Methods: SVC, STATCOM, synchronous condenser, capacitor banks
   • Comparison of methods
4. 7 Marks
   bExplain the basic operating control schemes the static Series Synchronous compensator with the help of a suitable diagram.
   How to answer

   • Structure of SSSC: VSC with series transformer
   • Operating principle: injected synchronous voltage
   • Control schemes: constant reactance, voltage, power flow
   • Phasor diagram and characteristics
5. 7 Marks
   aExplain the working principle of the Interline Power Flow Controller with the help of a suitable diagram.
   How to answer

   • IPFC configuration with multiple series converters and common DC link
   • Working: real power exchange between lines
   • Control of power flow in each line
   • Diagram of two-line IPFC system
6. 7 Marks
   bExplain the significance of harmonic current compensation using active filters.
   How to answer

   • Sources and effects of harmonic currents
   • Principle of shunt active filter compensation
   • Improvement in power quality and THD
   • Significance for system and equipment
7. 7 Marks
   aDiscuss the different applications of HVDC transmission and explain any one in detail.
   How to answer

   • List applications: long distance, submarine, interconnection, MTDC
   • Technical and economic aspects
   • Detailed explanation of any one application
   • Diagram of chosen application if relevant
8. 7 Marks
   bExplain the equivalent circuit representation of rectifier and inverter configurations.
   How to answer

   • Equivalent circuit of rectifier with voltage source and resistance
   • Equivalent circuit of inverter operation
   • Voltage-current relations Vd = Vd0 cos alpha - Rc*Id
   • Explanation of mode differences
9. 7 Marks
   aDescribe the inverter operation in HVDC systems.
   How to answer

   • Inverter operation with extinction angle gamma
   • Waveforms and commutation process
   • Relation between AC and DC quantities
   • Control requirements for inversion
10. 7 Marks
    bExplain the analysis of bridge converters with and without overlap.
    How to answer

    • Bridge converter operation without overlap (ideal)
    • Effect of source inductance causing overlap angle mu
    • Voltage waveforms and average Vd expression
    • Comparison of with and without overlap
11. 7 Marks
    aDiscuss the basic working principles of HVDC system control.
    How to answer

    • Hierarchy: converter, pole, system control
    • Constant current vs constant voltage control
    • Firing angle and extinction angle control
    • V-I characteristics of rectifier-inverter
12. 7 Marks
    bExplain the power reversal in HVDC systems and how is it achieved?
    How to answer

    • Principle: reversing DC voltage polarity, current direction same
    • Role of firing angle alpha > 90 deg change
    • Control sequence for reversal
    • Precautions and time required
13. 7 Marks
    aExplain the concept of Ignition Angle Control in HVDC systems.
    How to answer

    • Definition of ignition/firing angle alpha
    • Control by varying alpha to regulate Vd
    • Limits and effect on reactive power
    • Control characteristics
14. 7 Marks
    bDescribe the comparison between AC filters and DC filters.
    How to answer

    • Function and location of AC vs DC filters
    • Design aspects: harmonics filtered, rating
    • Comparison table on multiple basis
    • Need for both in HVDC stations
15. 14 Marks
    Write short notes on: (Any two)

    1. a)Static VAR Compensators (SVC)
    2. b)Power Flow Control in FACTS
    3. c)Comparison of Series and Parallel MTDC systems
    4. d)Unified Power Flow Controller (UPFC)
    How to answer

    • Definition and configuration of chosen topics
    • Operating principle and control
    • Applications and advantages
    • Neat labelled diagram