Impedance-Based Stability Analysis and Control of DC Cascaded System

This article comprehensively analyses the instability associated with constant power loads in DC-cascaded systems. The discussion focuses on the DC cascaded system, which consists of buck and boost converters supplying loads at constant voltage. The system rating is a 200 W buck converter that steps down the voltage from 48 to 24 V, supplying a resistive load and an additional 100 W buck and 30 W boost converter loads. Voltage-mode control is realized using the proportional-integral-derivative (PID) controller which enhances the DC grid stability. Further, the impedance-based interaction within the system is analyzed. MATLAB and PSIM simulation results are given to validate the analysis in ensuring the system stability under varying load conditions.