Thermally Constrained Optimized Pulse Patterns for Medium-Voltage Neutral-Point-Clamped Converters

A method of computing optimized pulse patterns with upper bounded junction temperatures of semiconductors is presented. An optimization-friendly thermal model with continuous first-order derivatives is derived, which models the junction temperature as a function of the switching angles of a pulse pattern. Expressions for the average, ripple, and instantaneous junction temperatures are derived. By constraining the junction temperature in the optimization problem underlying optimized pulse patterns, pulse patterns that guarantee thermally safe steady-state operation can be computed. This allows the thermal capabilities of semiconductor to be fully utilized, which typically enables a power increase of the converter system.