Digital control of high-switching-frequency dual active bridge converter using a real-time microcontroller

Abstract

This thesis investigates the digital voltage-mode control of high-switching-frequency dual active bridge converter using a Texas Instruments C2000 microcontroller. The motivation for this work stems from the recent use of wide-bandgap semiconductor switches, which enable higher switching frequencies and power densities but also impose a constraint on the available time for digital control law execution. This thesis examines the trade-off between control command update rate, achievable control loop bandwidth, transient response characteristics, and CPU utilization.

A DAB converter is controlled with the single-phase-shift modulation scheme in the Typhoon HIL404 hardware-in-the-loop simulator using the TI LAUNCHXL-F28379D development board as the digital control platform. A discrete-time small-signal model of DAB is used for PI controller design. Multi-cycle control is investigated by updating the phase shift command of DAB once every M switching cycles, which reduces the CPU’s control execution burden at the cost of increased loop delay.

Results show that for a fixed phase margin, increasing M reduces the achievable crossover frequency and CPU utilization. However, the transient response degrades when M increases, especially the load transient response. Results confirm that multi-cycle control can be a practical approach to reducing the computational burden on the digital controller in highswitching-frequency converters, especially when the loop bandwidth is low.