Remarks on the Behavior of a Multistable DC Drive in the Presence of Noise

Power electronic converters due to their inherent switching nature introduce nonlinearity in an electric drive system. That is sometimes exhibited in the form of the coexistence of several stable regimes (or attractors) for the same set of parameters and inputs, referred to as multistability. We study the behavior of a chopper-fed DC drive for the several sets of parameters and inputs, when the system exhibits multistability, in the presence of noise. In particular, we qualitatively characterize the coexisting attractors by what we call their robustness to noise, by comparing the level of noise required to observe the noise-induced tipping from one attractor into another. We depict that the “main” attractor (related to the nominal operation of the drive) is the most robust-to-noise one among the coexisting for all cases being analyzed. In those terms we explain the drive's behavior in the noisy environment―whether the effect of multistability takes the form of tipping or intermittency.