Stabilization Method for IPMSM with Long Electrical Time Constant Using Equivalent Resistance Gain Based on V/f Control

Abstract

This paper proposes a novel feedback control loop based on damping control in a V/f control for stabilizing interior permanent magnet synchronous motors (IPMSMs) with a long electrical time constant. A problem with the conventional damping control is that the ignored roots move to the unstable region due to the conventional damping gain K₁. In addition, the ignored roots are prone to become unstable because of its long electrical time constant. Therefore, a novel method is proposed to solve this instability problem. In this paper, first, a boundary condition of the stable region is derived based on the state equation. Then, a novel current feedback loop is added to the output voltage command. The experimental results show that the motor becomes unstable with the conventional damping control under a rated speed of 0.9p.u. and a rated torque of 0.7p.u. Under general operating conditions, the motor is stabilized by employing a novel feedback control loop.