Consider the following statements regarding HVDC Control:1.Constant current control is used in rectifier station.2.Constant extinction angle control is used in inverter station.3.Both stations operate under constant voltage control simultaneously.Which options stated above is/are correct?

Correct Answer: A - 1 and 2 only

Quick Concept Explanation

Line-commutated HVDC uses thyristors and depends on the AC system voltage for commutation, so adequate short-circuit strength and reactive-power support are important. AC voltage disturbances can produce commutation failure, particularly at the inverter. Key relation: LCC reactive demand is a significant fraction of transmitted power and is compensated locally.

Exam focus: Strong AC system and commutation margin matter for LCC. Common trap: LCC cannot normally operate a passive AC network without a voltage source.

Statement-wise Verification

• Statement 1 - Correct.
  Constant current control is used in rectifier station.
  Strong AC system and commutation margin matter for LCC.
• Statement 2 - Correct.
  Constant extinction angle control is used in inverter station.
  AC voltage disturbances can produce commutation failure, particularly at the inverter.
• Statement 3 - Incorrect.
  Both stations operate under constant voltage control simultaneously.
  Typical LCC-HVDC control coordinates current control at one terminal with extinction-angle/current-margin control at the inverter; both are not simply constant-voltage controllers

Core Concept

Line-commutated HVDC uses thyristors and depends on the AC system voltage for commutation, so adequate short-circuit strength and reactive-power support are important. AC voltage disturbances can produce commutation failure, particularly at the inverter.

Formula / Key Relationship

LCC reactive demand is a significant fraction of transmitted power and is compensated locally.

Why the Other Options Are Wrong

Option B is incorrect because it omits correct statement(s) 1. Option C is incorrect because it omits correct statement(s) 2. Option D is incorrect because it includes incorrect statement(s) 3.

Exam Shortcut / Approach

Strong AC system and commutation margin matter for LCC.

Common Mistake

LCC cannot normally operate a passive AC network without a voltage source.

Quick Revision

Constant Current and Extinction Angle Control is linked with HVDC Control, HVDC Transmission and Power Systems. Strong AC system and commutation margin matter for LCC.