Simplified Stability Analysis Method for Multiple Servo Drive Systems Connected to Common DC Bus Line

This paper proposes a simplified stability analysis method based on Middlebrook's method for multiple servo drive systems connected to the DC-bus line with the line inductance and resistance. The impedance of the DC-bus line causes interference among each current-control bandwidth for the motor. This paper reveals the relationship between the multiple servo drive systems stability limit and the DC-bus impedance with the simplified stability analysis method. The validity of the proposed method is demonstrated by comparison with the mathematical analysis and experiment results. As a result, the stability limit calculated by the proposed method is matched within an error of 2%. This paper also clarifies the cause of the errors between the mathematical analysis results and the experimental results in terms of regarding system loss.