DC-Link Capacitor Design in Neutral Point Clamped Multilevel Inverter Utilizing Ripple Current Analysis and DC-DC Converter Control

The DC-Link capacitor, an essential part in power converters, stabilizes voltage levels by reducing ripple effects, ensuring a constant output voltage despite high-frequency switching and transient load changes. This research focuses on designing a DC-Link capacitor for a 3-level, 3-phase neutral point clamped multilevel inverter (NPC-MLI). The design process involves calculating the current ripple and analyzing the RMS current in the capacitor. A well-designed DC-Link capacitor must account for ripple voltage and load variations. The proposed design includes cascaded control on the DC-DC converter, comprising both voltage and current controllers. This ensures the output current operates in continuous conduction mode (CCM), maintaining a continuous current flow to the DC-Link capacitor and reducing ripple voltage under load variations. MATLAB/Simulink simulations demonstrate this design's efficacy in a range of scenarios, highlighting the capacitor's role in maintaining the reliability and efficiency of power converters in renewable energy systems.