Finite Set MPC Algorithm for Achieving Thermal Redistribution in a Neutral-Point-Clamped Converter

The three level neutral-point clamped (3L-NPC) topology is one of the most widely used multilevel topologies in the low and medium voltage applications and also one of the most commercialized topologies. Although it offers many benefits compared to the conventional two level topology, it suffers from a considerable unequal loss distribution among the inner and outer switches and the clamping diodes. To solve this problem, we are proposing a control algorithm based on the finite control set model predictive control (FCS-MPC) that can provide a more balanced stress distribution. For implementing the proposed control algorithm no additional measurements are required nor thermal models of the semiconductor devices. The algorithm benefits are even more noticeable during low voltage ride through (LVRT) scenarios when the output voltage level of the converter is low and the current amplitude is high. Obtained simulation results confirm the positive effects on the thermal redistribution and also the junction temperatures of the most stressed devices are reduced. Effects of the algorithm are also verified on an experimental set-up.