Shuvangkar Das, PhD

3 minute read

During my PhD, I had the opportunity to work on one of the largest power system simulation projects in the state of New York—a 9 GW offshore wind farm integration study using EMT (Electromagnetic Transient) simulation. This project was part of New York’s ambitious plan to achieve clean energy targets, and the complexity was unlike anything I had worked on before.

The scope was massive. We were simulating eight offshore wind farms in detail—three HVAC-based and five HVDC-based connections. Each one had to be modeled with accuracy, and the interactions with the onshore grid—especially around New York City and Long Island zones—had to be studied under different operating and fault conditions.

“The offshore wind farms will account for nearly 25% of the total state’s power generation and mainly penetrate the New York City and Long Island zones,”
— Thomas Ortmeyer, Director of Clarkson’s Center for Electric Power System Research1

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⚡ The Question That Changed My Understanding

While working of the models and running EMT simulations, one question kept hitting me:

Why were most of the offshore wind farms using HVDC for exporting power to shore, and not HVAC?

It felt counterintuitive at first. After all, HVAC is more familiar and often cheaper in short-range transmission. So I started digging deeper. Here’s what I learned—summarized for anyone wondering the same.

🔌 HVAC vs HVDC: What’s the Technical Deal?

📉 AC (HVAC) Transmission Limitation Over Distance

One of the major drawbacks of HVAC cables—especially submarine ones—is charging current. The longer the cable, the more reactive power it produces, limiting how much real power you can transmit.

  • The charging current grows with distance and voltage, which means you can’t use the entire current-carrying capacity for actual power delivery.
  • This means HVAC becomes inefficient and costly as distance increases.

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As shown above, the transmission capacity of HVAC submarine cables declines rapidly beyond 80–100 km, even with higher voltage levels.2

⚙️ Why HVDC Works Better for Offshore Wind

  • No charging current: HVDC doesn’t suffer from capacitive charging losses.
  • Lower transmission losses: Especially over long distances, HVDC transmits power more efficiently
  • Higher power density: More power can be transmitted per conductor.
  • Better voltage control: Less affected by impedance and voltage drops, making it more stable for weak grid conditions.
  • Easier integration into grid codes: Especially with VSC-HVDC, the converter can be tuned for specific grid behaviors.

💡 Summary: Why HVDC is the Go-To for Offshore Wind

When the offshore wind farm is more than 80–100 km away from shore, HVAC becomes uneconomical due to:

  • High reactive power generation
  • Power transmission limits
  • Need for costly compensation equipment

On the other hand, HVDC systems shine for such cases by:

  • Enabling efficient long-distance power export
  • Reducing cable and system losses
  • Supporting large-scale renewable integration

🧠 Final Thought

That one question during my PhD—“Why HVDC?”—led me down a path of understanding not just simulation, but real-world engineering decisions in power systems. I realized that every transmission design choice is a balance of distance, capacity, stability, and economics.

If you’re working on power system planning, especially in the era of renewables, understanding HVDC vs HVAC trade-offs is not optional—it’s fundamental.

👋 About Me

Hi, I’m Shuvangkar Das, a power systems researcher with a Ph.D. in Electrical Engineering from Clarkson University. I work at the intersection of power electronics, DER, IBR, and AI — building greener, smarter, and more stable grids. Currently, I’m a Research Engineer at EPRI (though everything I share here reflects my personal experience, not my employer’s views).

Over the years, I’ve worked on real-world projects involving large scale EMT simulation and firmware development for grid-forming and grid following inverter and reinforcement learning (RL). I also publish technical content and share hands-on insights with the goal of making complex ideas accessible to engineers and researchers.

📺 Subscribe to my YouTube channel, where I share tutorials, code walk-throughs, and research productivity tips.

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📚References

[[Why HVDC Transmission Line is Superior]]

  1. https://www.nypa.gov/news/press-releases/2020/20201106-clarkson ↩

  2. H. Pfeifenberger, J. Tsoukalis, and S. Newell, “The Benefit and Cost of Preserving the Option to Create a Meshed Offshore Grid for New York,” 2021. ↩

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