Hello,
I have a question regarding the zero-sequence voltage injection in three-phase SSTs with bypassed modules in a failure case. I investigated some literature and it is clear that only the fundamental harmonic can shift power between the 3 arms (for power balance).
A 3rd harmonic is often used to reduce the peak arm voltages (-13.4%). However, I investigated asymmetrical fault cases and a 5th and 7th harmonic can help tofurther reduce the arm voltage by a small percentage like 5% (so less redundant modules are needed):
Conference Paper Adaptive Zero-Sequence Voltage Injection for Modular Solid-S...
My question is: Do you know other methods to handle asymmetrical fault conditions in cascaded H-bridges or SSTs? Can I handle grid-imbalances like module faults, since the modules in the phase with an over-voltage have to transmit more power (if no zero-voltage injection takes place)?
I thank you for your suggestions and ideas.
Or do you have experience in three-phase systems with a floating star point potential?
The new method is published here: https://ieeexplore.ieee.org/abstract/document/9570542
Your feedback is very welcome in this discussion or in private chat.