Analysis of Current Control Bandwidth in Current Source Type Motor Emulator

This paper focus on the stability issue of an inverter test system with a current source type motor emulator (CSTME). The CSTME imitates various motor operations with accuracy. However, the CSTME requires high current control bandwidth to prevent interference between the current controls of both the inverter under test (IUT) and the CSTME. This paper reveals the required current control bandwidth, which is to prevent interference between current controls, based on root locus analysis results. From the result of the stability analysis, the current controller of the CSTME requires 2.2 times higher bandwidth than IUT’s bandwidth. The stability limit of the root locus analysis agrees with the simulation of the time domain. In addition, the effect to the stability limit with time delay is also investigated. Then, the CSTME’s required current control bandwidth becomes more than 3.1 times of that of IUT. The validity of the analysis is verified by the simulation on the time domain.