Stabilization of Cascaded Power Converters Using Enhanced Model Predictive Control

Due to the rapid development of renewable energy technologies, energy storage technologies have also been extensively investigated. Recently, cascaded power converters have gained great attention for developing energy storage systems. In this paper, the instability issue of voltage source converters driving constant power loads is investigated. Based on the Nyquist criterion, the instability can be explained in the impedance model. A few examples are given to illustrate this kind of instability. The key to avoiding instability is to decrease the output impedance of the source converter, which can be done by Model Predictive Control (MPC). An enhanced model predictive control with impedance compensation, is proposed in this paper to avoid instability. A DC system example and an AC system example are given to verify the proposed method.