Nonlinear Model Predictive Control for Active DC-Link Systems

In various power electronic converters bulky capacitors are used as passive energy buffers on the dc bus. In order to reduce the capacitance, some solutions have been proposed to replace these with active energy buffering circuits. These active buffering circuits, or active dc-links, are nonlinear systems. This poses a challenge in applications which must buffer highly transient currents composed of many different frequencies. This paper presents a nonlinear model predictive (NMPC) control scheme that makes use of state and disturbance predictions to accurately control an active dc-link system to provide better buffering capability and provide integrated constraint handling. Simulation of the NMPC control scheme and active dc-link system show the effectiveness of the control scheme and some potential for further capacitance reduction.