ABB Swiss Ltd. has applied for a patent titled “Method and Computer Program for Controlling an Electrical Converter, Controller for Controlling an Electrical Converter, Electrical Converter and Computer-Readable Medium” (publication number CN121079887A, filed in April 2024).

The invention relates to a power converter system and a corresponding control method designed to improve operational reliability under fault conditions. The converter includes a main stage, a filter unit stage, and three bypass switches. The main stage converts DC voltage into a three-phase intermediate voltage, with each phase handled by a dedicated output. The filter unit stage consists of three filter units, each connected to a corresponding main output to modify the intermediate voltage. The bypass switches are used to selectively bypass any faulty filter unit while maintaining power delivery to the converter output.

In normal operation, the system determines a main-stage pulse pattern based on a reference output voltage signal. A corresponding filter-unit pulse pattern is also generated based on a derived voltage reference. Both patterns define switching timings for the next modulation cycle to ensure stable output voltage generation.

When all filter units operate normally, the converter applies switching commands based on both the main-stage and filter-stage pulse patterns. However, if one filter unit fails, the system activates the corresponding bypass switch and modifies the control strategy. In this fault scenario, the failed unit is effectively excluded, and the system recalculates a modified pulse pattern assuming zero contribution from the faulty unit. The remaining healthy filter units then compensate by adjusting their operation to maintain the required three-phase output voltage.

This adaptive control approach ensures continuous converter operation even during partial hardware failure, improving system robustness, fault tolerance, and overall reliability in industrial power conversion applications.