Analysis of high-frequency oscillation mechanism of inverter with motor load based on series resonance

Abstract

Inverter-driven asynchronous motor loads represent typical operational scenarios in shipboard integrated power systems. The inverter’s output impedance characteristics are influenced by complex control dynamics, and the interaction between source and load impedances presents a risk of high-frequency resonance. To address this, this paper first uses the harmonic linearization method to establish sequence impedance models of the inverter and asynchronous motor. It analyses the high-frequency impedance characteristics of the source and load, developing an equivalent high-frequency RLC circuit model. The oscillation mechanism is revealed from the perspective of system series resonance. Specifically, when the positive resistance of the load subsystem at the series resonance frequency cannot counteract the negative resistance effect of the source subsystem, the system’s series resonance high-frequency oscillation mode exhibits negative damping characteristics, leading to instability. Secondly, to quantitatively evaluate system stability, the aggregated impedance stability criterion is derived from the Nyquist stability criterion. This criterion is used to analyse the influence of inverter control parameters and motor power on stability. Results indicate that as the proportional coefficient of voltage loop increases, the voltage feedforward coefficient increases, and the current feedforward coefficient decreases, the system’s high-frequency oscillation stability margin decreases. However, motor with higher power improve stability.