A Zero Net Flux Modulation Scheme for 3-Leg Core Transformer Based 3-Phase AC–DC Topologies
Bibliographic record
Abstract
Existing single-stage 3-phase ac–dc isolated topologies typically use three separate C-core high-frequency transformers (HFTs), which require significant space and reduce power density. A key challenge preventing the use of a more compact 3-leg core HFT is the lack of suitable modulation schemes, as current methods do not ensure a zero net flux condition considering all 3 legs. Violating this condition can lead to stray fluxes that induce common mode (CM) currents and high peak magnetizing currents, resulting in increased electromagnetic interferences and losses. This article proposes a new modulation scheme that, by strategic alignment of switching pulses for a dual inverter setup, both avoids CM winding voltage generation and preserves the shape of transformer secondary-side voltage waveforms for power transfer at twice the carrier frequency. These features allow the use of a single compact 3-leg core HFT. The scheme also offers: 1) high-quality 3/5-level ac pulse-width modulated grid voltages, 2) a 3-level high-frequency voltage for the power transmitted via transformer action, 3) higher overall average winding volt–seconds compared to dual active bridge converters at low modulation indices, and 4) reduced switching losses due to the discontinuous nature of the scheme. Adopting a 3-leg core can cut the size of 3 C-core designs by 35%–40% while achieving 4% total current harmonic distortion at full load. The presented modulation scheme is verified using both simulation and experimental results for a 250 V<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{{\text{dc}}}$</tex-math></inline-formula>, 122 V<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{\text{ac}}$</tex-math></inline-formula>, 750 W prototype.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".