Four-Level Inverter with Variable Voltage Levels for Hardware-in-the-Loop Emulation of Three-Phase Machines

In order to emulate the behavior of three-phase machines in a hardware-in-the-loop test bench, an applicable power electronic device is required. For this purpose, an inverter concept with four variable voltage levels per phase is presented. This concept precisely fulfills the requirements of three-phase machine emulation. The presented inverter is theoretically able to adjust the ideal countervoltage course which is needed to emulate three-phase machines' electrical behavior. In contrast, the countervoltages of commonly used power electronic devices suffer from deviation caused by switched-mode operation or limited bandwidth. Within this paper the setup of the four-level inverter is presented. Besides, the paper discusses a control strategy for operating the four-level inverter as a three-phase machine emulator.