Consider the following statements regarding the suitable choice of HVDC converter configuration:1.Pulse number should be high2.Ratio of peak inverse voltage to no load d.c. output voltage should be as high as possible3.Transformer utilization factor should be nearly unityWhich of these statements are correct?

Correct Answer: C - 1 and 3 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.
  Pulse number should be high
  Strong AC system and commutation margin matter for LCC.
• Statement 2 - Incorrect.
  Ratio of peak inverse voltage to no load d.c. output voltage should be as high as possible
  A desirable converter configuration minimizes device PIV requirement relative to useful DC output, not maximizes it
• Statement 3 - Correct.
  Transformer utilization factor should be nearly unity
  Strong AC system and commutation margin matter for LCC.

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

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

Pulse Number PIV and Transformer Utilization is linked with Converter Configuration, HVDC Transmission and Power Systems. Strong AC system and commutation margin matter for LCC.