Skip to content

Dual Active Bridge (DAB) Converter Example

Bidirectional isolated DC-DC converter.

Overview

The DAB converter provides: - Bidirectional power flow - Galvanic isolation - Soft switching capability - High power density

Specifications

Parameter Value
Port 1 Voltage 400V DC
Port 2 Voltage 48V DC
Power Rating ±3 kW
Switching Frequency 100 kHz
Transformer Ratio 8:1
Leakage Inductance 50 µH

Circuit Files

  • dab_basic.ipes - Basic DAB operation
  • dab_bidirectional.ipes - Forward and reverse power flow
  • dab_sps.ipes - Single phase shift modulation

Theory

Operating Principle

Two H-bridges connected through high-frequency transformer:

       H-Bridge 1      Transformer     H-Bridge 2
V1 ──┤           ├──────┤ n:1 ├──────┤           ├── V2
     └───────────┘      └─────┘      └───────────┘

Phase Shift Modulation

Power transfer controlled by phase angle φ between bridges:

\[P = \frac{V_1 \cdot V_2'}{2\pi f_s L} \cdot \phi \cdot (1 - \frac{|\phi|}{\pi})\]

Where V2' = n × V2

Key Equations

Maximum Power: $\(P_{max} = \frac{V_1 \cdot V_2'}{8 f_s L}\)$ (at φ = π/2)

ZVS Condition: Sufficient current at switching instant for capacitor discharge.

Modulation Strategies

Single Phase Shift (SPS)

  • Simplest control
  • 50% duty cycle on both bridges
  • Phase angle controls power

Extended Phase Shift (EPS)

  • Inner phase shift added
  • Wider ZVS range
  • Reduced circulating current

Dual Phase Shift (DPS)

  • Both bridges have inner shift
  • Optimized for efficiency
  • More complex control

Bidirectional Operation

Direction φ Sign Power Flow
Forward φ > 0 V1 → V2
Reverse φ < 0 V2 → V1

Exercises

  1. Power vs Phase Shift: Verify transfer characteristic
  2. ZVS Boundary: Find minimum load for ZVS
  3. Bidirectional: Reverse power flow
  4. Efficiency Comparison: SPS vs EPS

Applications

  • Battery energy storage systems
  • EV charging (V2G capable)
  • Solid-state transformers
  • DC microgrids