Bidirectional AC/DC Converter using GaN HEMT based Non-Isolated DAB for Battery Emulation

Battery Emulators (i.e. controllable power supplies with non-linear output) are ubiquitous test equipment in grid-to-vehicle AC/DC (for onboard charger), electric motor drives DC/AC, renewable energy (such as two stage solar DC/AC) nowadays. The topology choice is usually not optimized in commercial off-the-shelf battery emulators. In this work, using the 'fractional power conversion' architecture a GaN based non-isolated (isolation is lost due to architecture) Dual active-bridge (DAB) DC/DC converter is chosen to emulate the battery terminal voltage and current. To allow bidirectional power flow, the converter is interfaced with a GaN based PFC totem-pole AC/DC converter to allow both battery charging and discharging behaviors to be emulated. Both input side PFC AC/DC and output side DC/DC converters are designed using CoolGaN devices. In fractional power architecture, the main focus is usually reducing the footprint of the converter. In this work, attention is reducing control effort for a given power demand therefore the modifications introduced by the bus bars that connect the input port to the output port to create the fractional power conversion architecture as well as modulation scheme choice that allows better utilization of the semiconductor has been studied.