📋 Case Study

UK National Grid Hornsea Offshore Wind Integration

Harmonic resonance amplification at 11th/13th harmonics causing capacitor bank failures

🏗️ Project Overview

1.2 GW offshore wind farm connected via ±320 kV HVDC link to onshore grid with aging 400 kV network

🎯 Challenge

Harmonic resonance amplification at 11th/13th harmonics causing capacitor bank failures

🔧 Design Approach

Passive harmonic filters + active harmonic cancellation in VSC-HVDC converters + impedance shaping via transformer tap optimization

📐 Key Calculations

Resonant Frequency Shift

f_r = 1/(2π√(L_filter × C_bank))

Result: 287 Hz → 262 Hz

Moved away from 11th harmonic (275 Hz)

THD Reduction Estimate

THD_new = THD_old × (Z_system / Z_total)

Result: 4.2% → 1.7%

Below EN 50160 limit of 3%

📊 Results

Zero capacitor failures in 3 years; THD maintained <2.1% across all monitoring points

💡 Lessons Learned

• •Transformer leakage reactance significantly impacts filter tuning
• •HVDC converter harmonic injection spectra must be validated under partial loading

✅ Key Takeaways

• 1Transformer leakage reactance significantly impacts filter tuning
• 2HVDC converter harmonic injection spectra must be validated under partial loading