Digital Control of a 600-V to 28-V 20-kW Two-Stage DC-DC Converter

A trend of increasing powertrain voltages is seen in electric vehicles and more electric aircraft. However, the systems close to humans have stayed at 12 to 48 V for safety reasons. A combination of control and converter architecture is needed to efficiently meet the required gain over all line and load conditions. This work briefly introduces a converter architecture and, in detail, demonstrates a digital control technique for a 600 V to 28 V 20 kW two-stage DC-DC converter. A modular input-parallel output-parallel (IPOP) configuration with two identical 10 kW modules is used. Each module consists of a buck stage for regulation followed by a series-resonant DC transformer (SR-DCX) for isolation and a fixed gain. A current sharing compensator is designed to ensure equal current sharing between IPOP modules. The control technique considers constraints due to signal-chain processing and minimizes digitization delays. The scheme experimentally demonstrates robust control over the required line and load variations for the 10 kW module. The devised control technique demonstrates equal current-sharing amongst the paralleled modules using a PLECS simulation.