FPGA-Based High-Bandwidth Motor Emulator for Interior Permanent Magnet Machine Utilizing SiC Power Converter

A high-bandwidth (>20 kHz) motor emulator (ME) prototype for ac machines, utilizing field programmable gate array (FPGA)-based hybrid model predictive control (MPC) and a high fidelity motor model and implemented with a voltage source power converter, and fast-switching SiC devices, is presented in this article. The hybrid MPC incorporates a unique gate stitching modulation strategy that synchronizes the inverter switching state with the ME switching state for an accurate representation of the emulated motor currents in the physical inverter hardware output. The gate stitching MPC hybrid algorithm avoids the need for an excessively high switching frequency of the ME power converter. The developed high-bandwidth ME can emulate up to the switching ripple current of the inverter under test (IUT) where the current slope can change up to six times within one switching period when using space vector pulse width modulation (PWM). The FPGA-based fast iterating online motor model is another key component which along with the high-performance ME current regulation algorithm can accurately emulate the motor current. The bandwidth achieved far exceeds that of existing ME solutions that can only emulate fundamental current and only a few orders of harmonic content. The high bandwidth also allows the use of a small line inductor, which reduces the size and cost of the ME system. Simulation and experiment results are provided to the FPGA implementation and validate the high-bandwidth current emulating capability.