DAB Designer & Control Laboratory

Control Parameters

30°
50 kHz
25 μH
175 kW
ZVS Achieved
Margin: 15%
175
Power (kW)
98.2
Efficiency (%)
125
I_rms Pri (A)
450
I_rms Sec (A)

Real-Time Waveforms

DAB Control Theory

Single Phase-Shift (SPS) Modulation

The fundamental DAB control method where power transfer is controlled by the phase shift between primary and secondary bridge voltages. This method provides simple control but limited ZVS range.

Power Transfer Equation (SPS):
\[ P_{SPS} = \frac{n \cdot V_1 \cdot V_2}{2\pi f_s L_{lk}} \cdot \phi \left(1 - \frac{|\phi|}{\pi}\right) \]

Dual Phase-Shift (DPS) Modulation

Extends SPS by introducing an internal phase shift in one bridge, providing an additional degree of freedom for optimizing efficiency and extending ZVS range.

Power Transfer Equation (DPS):
\[ P_{DPS} = \frac{n \cdot V_1 \cdot V_2}{2\pi f_s L_{lk}} \cdot \left[\phi_1 - \phi_2 + \frac{\phi_2^2 - \phi_1^2}{2\pi}\right] \]

Triple Phase-Shift (TPS) Modulation

The most flexible control method with three degrees of freedom, enabling optimal efficiency across the entire operating range while minimizing circulating current.

Power Transfer Equation (TPS):
\[ P_{TPS} = \frac{n \cdot V_1 \cdot V_2}{2\pi f_s L_{lk}} \cdot f(\phi_1, \phi_2, D) \] where \( f \) is a complex function of all three control variables

Intelligent Optimization

Multi-Objective Optimization

Utilize machine learning algorithms to find optimal operating points considering:

  • ✓ Efficiency maximization
  • ✓ ZVS range extension
  • ✓ Circulating current minimization
  • ✓ Thermal stress reduction

Optimization Results

Parameter Current Optimized Improvement
Efficiency 98.2% 98.7% +0.5%
Circulating Current 45 A 28 A -38%
Switching Loss 2.8 kW 1.9 kW -32%
ZVS Margin 15% 25% +67%

Experimental Validation

Test Conditions

  • • Input Voltage: 19.5 kV DC (from NPC rectifier)
  • • Output Voltage: 800 V DC (to LV converter)
  • • Transformer Ratio: 9.33:1
  • • Core Material: Vitroperm 500F Nanocrystalline
  • • Primary Devices: Wolfspeed CAB450M12XM3 SiC MOSFETs
  • • Secondary Devices: GaN Systems GS66516T GaN HEMTs

Design Guidelines

Leakage Inductance Selection

Optimal Llk balances ZVS achievement with circulating current. Target 5-10% of base impedance:

\[ L_{lk,opt} = \frac{V_{dc}^2}{8 \cdot f_s \cdot P_{rated}} \]

Dead-Time Calculation

Dead-time must ensure complete charge/discharge of device output capacitance:

\[ t_{dead} = \frac{4 \cdot C_{oss} \cdot V_{dc}}{I_{ZVS,min}} \]

Switching Frequency

Higher fs reduces transformer size but increases switching losses. Optimal range: 20-100 kHz

\[ f_{s,opt} = \sqrt{\frac{P_{core}}{P_{sw}}} \cdot f_{nom} \]