Three-level H-bridge and three H-bridges-based three-phase four-wire shunt active power filter topologies for high voltage applications

• Development of 3HB and 3L-HB topologies for three-phase four-wire shunt active filter.
• Both topologies are suitable for high voltage, medium to high power applications.
• Real-time analysis under various supplies and unbalanced loads with Opal-RT Lab.
• Comparison of 3L-HB and 3HB topologies of shunt active power filter.
• Choice of either indicates a compromise over cost and compensation capability.

In a three-phase four-wire distribution system, presence of current harmonics, unbalanced loading, reactive power and excessive neutral current play the most important role in deciding power quality. Main culprits behind these are the disturbances caused due to non-linear and unbalanced loads. Here a new three-level H-bridge (3L-HB) topology of three-phase four-wire shunt active power filter (APF) has been developed for load compensation. This can be connected to the distribution lines directly, and does not require any bulky and expensive coupling transformers. Furthermore, this topology of shunt APF has been compared with two-level three H-bridges (3HB) based topology. The performances of APFs are investigated with the help of real-time performance analysis in Opal RT-Lab. A comparison has been made between the two configurations showing their topological differences and load compensation capabilities under ideal, distorted and unbalanced supply voltage conditions. Observations are done taking into consideration the unbalanced loading scenario that is when both three-phase and single-phase loads are present in the system.