Design for Reliability (DFR) of DC-Link Capacitors for Multilevel Inverter Topologies Operating in Hostile Environments

Especially in the mining industry, Pulse Width Modulated Voltage Source Converters (PWM-VSC) driving induction motors at long distances from the inverter is common. Due to the long cable used for the converter-to-motor connection, several unwanted high-frequency phenomena occur. A new configuration for these motor drive systems was previously proposed to address this situation. The new configuration involves keeping the rectifier in its original location, while the inverter bridge is installed close to the motor terminals, and long cables are used as a DC transmission line. The environment in which the inverter will now be located is more hostile and can compromise the inverter’s lifetime. This situation creates new concerns about the system’s reliability, despite the various advantages of this new configuration. This paper presents a study on the reliability of the DC-Link capacitors for Three Level Neutral Point Clamped (3L-NPC) and Three Level Active Neutral Point Clamped (3L-ANPC) inverter topologies when operating in aggressive environments. For this purpose, methodologies based on Physics of Failure (PoF) and Design for Reliability (DfR) were used. In this sense, an investigation was conducted to find the configurations best suited to improve the solution regarding reliability, cost, energy, and volume.