Three-phase dual converter structure A three-phase dual converter (for four-quadrant DC drive operation) is built using which pair of rectifier modules?

Introduction / Context:
Dual converters provide reversible DC voltage and current for four-quadrant motor drives. They achieve this by pairing two controlled rectifier bridges so that the DC polarity can be reversed without reversing motor leads.

Given Data / Assumptions:

• Need for both rectification and inversion in both current directions.
• Each bridge should be fully controlled to allow voltage reversal via firing angle control.

Concept / Approach:
Two fully controlled six-pulse bridges connected in antiparallel across the DC terminals allow the system to develop positive or negative average DC voltage with controlled current direction. Interbridge reactors or circulating-current control manage power flow between bridges.

Step-by-Step Solution:
Choose full converters → enable positive and negative V_dc by varying α.Connect antiparallel on the DC side → one bridge feeds in one polarity, the other in the opposite.Implement circulating-current or non-circulating control for safe operation.

Verification / Alternative check:
Drive textbooks depict dual converters explicitly as back-to-back fully controlled bridges (not semiconverters) to ensure full four-quadrant capability.

Why Other Options Are Wrong:
Semi-converters: Half-controlled bridges cannot provide symmetric bidirectional voltage control.
Parallel connection: Does not reverse DC polarity and risks cross-conduction.

Common Pitfalls:
Confusing antiparallel (DC opposition) with paralleling on the AC side; the key is DC opposition for polarity reversal.

Final Answer:
two 3-phase full converters connected in antiparallel