Power Quality

15 kW, 3-Phase Vienna Rectifier Reference Design with SiC FETs and Mixed-Signal Control

The STDES-VIENNARECT reference design from STMicroelectronics represents a complete solution for high power three-phase ac-dc rectifier applications based on the Vienna topology. It features mixed-signal control, with the STNRG388A controller providing digital output voltage regulation, and dedicated analog circuitry providing high bandwidth continuous conduction mode (CCM) current regulation for maximum power quality in terms of total harmonic distortion (THD) and power factor (PF).

The high switching frequency of the SiC MOSFETs (70kHz) and the multilevel structure allow nearly 99% efficiency as well as the optimization of passive power components in terms of size and cost.

This high efficiency Vienna rectifier is designed for several end applications such as electric vehicle (EV) and industrial battery chargers, and industrial equipment requiring very high PF and low THD.

STDES-VIENNARECT block diagram (click on image to enlarge)

This reference design consists of the following separate components:

  • Power board with power section, EMI filter, sensing circuit, inrush circuit and auxiliary power supply.
  • Control board based on the STNRG388A 8-bit digital controller for power conversion applications, along with connectors for communication, and test-points and status indicators for testing and debugging.

The input and output current and voltage measurements necessary for responsive control are acquired through isolated measurement blocks, and the control section allows analog implementation of CCM current regulation for power factor correction, while the bus voltage is regulated through digital control.

The STNRG388A provides comprehensive control of the application currents and voltages as well as monitoring and protection, plus the start-up sequence and load variation control. The driving signals of the switching devices are determined by an internal State Machine Event Driven (SMED), ensuring that time critical tasks are never interrupted.

Summary of Key Features:

  • 3-phase, 3-level ac-dc power converter
  • Rated nominal output DC voltage: 800Vdc
  • Rated nominal input AC voltage: 400Vac at 50Hz
  • Nominal output power ac-dc: 15kW
  • Power factor, PF>0.99
  • Inrush current control and soft start-up
  • THD lower than 5% at nominal operation
  • Power section based on SiC MOSFETs and diodes:
  • High frequency operation (70 kHz)
  • High peak efficiency greater than 98%
  • Passive element weight and size reduction
  • Control section based on programmable STNRG388A digital controller
  • Low cost mixed-signal control
  • Overcurrent and overvoltage protections
STMicroelectronics NV
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