Study on the key-problems for digital controlled multiple parallel active power filter

Multi-modular approach has been used recently in some power electronics equipments to achieve large power rating, better reliability, manufacturability, and maintainability. This paper introduces the development of a practical 100kVA active filter employing this multi-converter approach and having an additional benefit of improving equivalent switching frequency. The control circuit was implemented with a flexible dual-DSP processor digital system for the active filter. The operation principle, signal detection method, circuit configuration and detailed control method are introduced in the paper. Industrial tests showed that the compensating performance is very good. The equipment functions very well, and the control circuit and the multiconverter approach are valid. The EMC problem generated by the APF has also been discussed and bated in paper.