Out of the following which multipulse converter is mostly used in HVDC?

Question

Examoogle · Accepted Answer

Option C: 12-pulse converter

Explanation & Concepts:
The 12-pulse converter is the industry standard for HVDC transmission systems due to its superior harmonic performance compared to 6-pulse configurations. By utilizing two 6-pulse bridges connected in series, the AC side harmonics of order $6n \pm 1$ (where $n$ is odd) are effectively cancelled, leaving only $12n \pm 1$ harmonics.

Working Principle: A 12-pulse converter consists of two 6-pulse bridges fed by transformers with a $30^{\circ}$ phase shift (one star-star and one star-delta). This phase displacement ensures that the characteristic harmonics generated by one bridge cancel those of the other. This significantly reduces the size and cost of the required AC filters.

Key Formulas: $h = 12n \pm 1$ — Harmonic orders generated by a 12-pulse converter; $V_{dc} = 2 	imes \frac{3\sqrt{2}}{\pi} V_{LL} \cos(\alpha)$ — Average DC output voltage of a 12-pulse converter

Key Points: Eliminates 5th and 7th order harmonics entirely from the supply side.; Higher ripple frequency ($12 	imes f$) reduces the size of DC side smoothing reactors.; Predominant harmonics are $11^{th}$ and $13^{th}$, which are easier to filter.; Consists of two series-connected 6-pulse bridges.

Advantages: Lower harmonic distortion; Reduced requirement for AC filtering components; Higher voltage output capacity

Disadvantages: Requires complex transformer configurations ($Y-Y$ and $Y-\Delta$); Increased capital cost due to extra components

Applications: HVDC Transmission terminals; Large-scale Industrial rectifiers; High-power STATCOMs

Additional Info: The 12-pulse system is the fundamental building block of modern HVDC 'poles'.. Option A (6-pulse) produces high harmonic distortion (5th, 7th). Option B (18-pulse) exists but is rarely used due to excessive complexity/cost.

Answer: C is correct — The 12-pulse converter is standard in HVDC because its phase-shifted transformer arrangement cancels low-order harmonics, significantly improving power quality.

Exam Tip: Always remember that in power electronics, increasing the number of pulses effectively pushes the harmonic frequencies higher, making them significantly easier and cheaper to filter using passive LC circuits.

Examoogle · Answer

Option A: 6-pulse converter

Examoogle · Answer

Option B: 18-pulse converter

Examoogle · Answer

Option D: 7-level multilevel inverter

Correct Answer

Discussion (0)

Correct Answer

Related Questions

Discussion (0)