Dual Active Bridge Converter with ESP32 Control

Dual active bridge design + Circuit test

Project Overview

The project focuses on designing and implementing a DAB converter with the following features:

• Phase-Shift Control: Regulates power using phase-shift modulation.
• High Precision: Utilizes the AD7190 ADC for accurate voltage and current measurements.
• PID Regulation: Maintains desired output voltage via a PID controller.

Hardware Components

• Microcontroller: ESP32
• ADC: AD7190 (24-bit Sigma-Delta ADC)
• Power Stage:
  • MOSFETs: IRF540N
  • Transformer: Custom-designed with turns count ( Np = 15, Ns = 3 ), core EE25/9/6.5
  • Inductor: 12.4 µH (Removed due to high transformer leakage inductance)
  • Capacitor: 1328 µF
• Gate Driver: IR2103

Note: I've used Tim McRae's DAB design youtube video in this design. youtube video link: https://www.youtube.com/watch?v=w5SGHoz5zPE Results from the video are written in a MATLAB file for easy calculation.

Software Components

• MCPWM Configuration: Uses the ESP32's Motor Control PWM module to generate phase-shifted PWM signals.
• AD7190 Driver: Interfaces with the ADC for precise measurements. (by @gism)
• PID Control: Adjusts phase shift to regulate output voltage.
• Serial Communication: Enables setpoint adjustment via serial input.

Transformer Design

The transformer is optimized for the DAB converter with these specifications:

• Turns Ratio: ( n = 0.2 ), minimizing inductor current ripple at 25 V input.

• Core: EE25/9/6.5 ferrite, selected based on window area product (WaAc) of 2678.57, calculated using:

  • Output Power: 50 W
  • Current Density: 750 Circ Mil/Amp
  • Topology Factor: 0.0014 (Full-bridge)
  • Max Flux Density: 1000 Gauss at 100 kHz
  • Switching Frequency: 100 kHz

  Note: Transformer was designed with help of this article

Control Mechanism

Power transfer is regulated by adjusting the phase difference between PWM signals driving the H-bridges. In the ESP32, this is achieved using the MCPWM module:

• PWM phase difference was achieved by tackling with MCPWM dead time modules. first a pair of identical PWM signals are created. then both rising-edge and falling-edge dead times added to one of PWM signals to make a phase difference with the other PWM signal.
• Dead time adjustments shift the PWM signals, controlling the power flow direction and magnitude.

void update_phase(double phase) {

  uint32_t pd = (phase / 180.0) * max_dt;

  //module 0
  REG_WRITE(0x3FF5E05C, (uint32_t)pd); //Shadow register for falling edge delay(FED)
  REG_WRITE(0x3FF5E060, (uint32_t)pd); //Shadow register for rising edge delay(RED)
  //module 1
  REG_WRITE(0x3FF5E094, (uint32_t)pd); //Shadow register for falling edge delay(FED)
  REG_WRITE(0x3FF5E098, (uint32_t)pd); //Shadow register for rising edge delay(RED)
  return;
}

Setup and Usage

Note: DAB main circuit schematic in proteus is also available

Note: I've used Serial Studio to monitor output data visually with graphs

Channel 1: Setpoint

Channel 2: Measured output voltage (in mili-volt)

Channel 3: Error

Channel 4: Shunt Resistor voltage (Shunt Res value: 0.008 Ohm)

Notes

• PID parameters may need tuning based on hardware specifics.

Contributor

• Amir Rahmani