Thermal Stress Reduction in Neutral-Point-Clamped Multilevel Converters Through a Switching-Cell Array-Based Implementation and Active Thermal Control

Conventional configurations for neutral-point-clamped multilevel converters exhibit an uneven power loss distribution among their power semiconductor devices. In particular, this imbalance increases the temperature of power semiconductor devices situated at specific locations within the converter layout, thereby reducing the reliability of the system. To mitigate this issue, neutral-point-clamped multilevel converters can be implemented using a switching-cell array design. This design allows for multiple topology configurations and inherently introduces redundant conduction paths, thus reducing conduction losses and also providing greater flexibility in distributing the switching losses. This work analyzes the thermal behavior of various configurations of a four-level dc–ac neutral-point-clamped converter based on a switching-cell array. An active thermal control strategy is used to distribute the switching losses, in order achieve a more uniform temperature distribution across the converter. Experimental results confirm that, compared to conventional neutral-point-clamped converter implementations, configurations based on a switching-cell array combined with active thermal control achieve a more uniform distribution of power losses. This leads to significantly improved temperature uniformity across the converter, thereby reducing thermal stress and enhancing overall system reliability.