Bandwidth Enhancement of Electric Machine Emulator With Virtual-Impedance Control

An electric machine emulator (EME) is becoming a popular solution to the characterization, testing, and validation of electric-machine-connected converters with complex mission profiles. Typically, a closed-loop current controller (CLCC) is implemented to regulate the current behaviors of the emulator. A high control bandwidth is necessary for the EME to ensure that the dynamic and high-frequency performances of the emulator are not distorted by the CLCC. However, the overenhanced control parameters of the CLCC will lead to compromised stability margin of the emulating converter. In this article, the limitations of typical control methods for the EME are analyzed, and a bandwidth-enhanced current control method, virtual-impedance control, is proposed to improve the dynamic performances and to expand the emulation range of the emulator. Compared with the typical control methods, the proposed approach is capable of enhancing the control bandwidth without increasing the control parameters or narrowing its stability margin. As a result, both the static and dynamic characteristics of the target electric machine can be accurately recreated, and the application range of the EME can be further extended. Experimental validations are conducted to demonstrate the effectiveness and superiority of the proposed control approach.