A New Hybrid Power Filter Topology Enabling Low Voltage Switching Devices and Storage Capacitors

The increasing importance of mains harmonic content problem has been responsible for several improvements in active power filter topologies in the last decade. The pure multiple half-bridge configurations are now becoming replaced by new hybrid topologies aiming to be both less bulky and expensive. This new technique consists in reducing the voltages at the storage capacitors and consequently at the switching devices. This is achieved, introducing an extra passive filter between mains and the converter, tuned at interest frequencies. The great majority of the solutions already studied in what concerns to this particular area concentrate their attention at specific characteristic loads or balanced three-phase systems. Power factor compensation in simple-phase and general three-phase systems becomes more difficult to achieve because of the fact that 3rd harmonic may/will no longer be null in these cases. Studies made at this paper reveal that in these last applications the solutions previously proposed become quite unsatisfactory. This paper presents a new shunt hybrid active filter topology that can reduce the converter voltage down to 5% of mains voltage amplitude even under the conditions described at the previous paragraphs. A simple, comparative study is presented, taking into consideration pure active solutions and a hybrid solution proposed by another author. Designing criteria and simulation results is also discussed