Modern HVDC converter pulse numbers Present-day line-commutated HVDC terminals most commonly use which converter configuration?

Introduction / Context:
HVDC systems convert AC to DC (and back) using phase-controlled bridges. Pulse number determines characteristic harmonics and filtering requirements. Modern practice favors configurations that minimize AC and DC harmonics.

Given Data / Assumptions:

• Line-commutated converter technology (thyristor LCC).
• Standard utility practice for harmonic mitigation.

Concept / Approach:
A 12-pulse converter is realized by series or parallel connection of two 6-pulse bridges fed by transformers with 30° phase shift. This cancels the lowest characteristic harmonics (5th and 7th on AC side), reducing filter size and improving power quality compared with a single 6-pulse bridge.

Step-by-Step Solution:
Assess harmonic content: 6-pulse → strong 5th/7th harmonics.Use phase-shifted pair → 12-pulse → cancels 5th/7th, leaving 11th/13th as lowest.Industry standardize on 12-pulse for bulk power HVDC terminals.

Verification / Alternative check:
Most classic HVDC schemes (e.g., monopole/bipole LCC) specify 12-pulse converter groups at each pole.

Why Other Options Are Wrong:

• 3-pulse is obsolete.
• 6-pulse only has higher harmonic burden.
• “Either 6 or 12” is too broad; modern practice predominantly uses 12-pulse.
• 18-pulse is uncommon and complex at HVDC ratings.

Common Pitfalls:

• Confusing with VSC-HVDC, which uses PWM converters rather than line-commutated bridges.

Final Answer:
12-pulse converters