Impedance-based Stability Analysis of Servo Drive DC Bus Systems

Abstract

Servo drive motor systems using PWM inverters have become very popular in the industrial market owing to their excellent control over torque, speed and position. Recently, problems of EMI noise and complexity of wiring from 3-phase PWM inverter power line cables have become critical issues in factories. In addition, using the regenerative energy of a motor has become important. A DC bus system can be a solution to these problems and demands. However, the DC bus system for servo drives has a risk of system instability because of interference between the DC bus and the servo drives. In this paper, an impedance-based stability analysis method is proposed that can predict the stability by only using the I/O (impedance) characteristics instead of all the system properties. The experimental results show that this method is useful.