Comparison of three-phase four-wire converters for distributed generation

To connect distributed generation units to a low-voltage four-wire distribution network, a suitable three-phase converter topology needs to be chosen. To improve the power quality in the grid, the distributed generation unit can be used as an active power filter (APF). When an active power filtering function is desired, the converter should have a neutral wire to allow neutral currents to flow. Therefore, two four-wire topologies, the four-leg and split-link converter, are compared in this paper. The comparison criteria are the ease of control, EMC performance, mid-point control, dc-bus voltage utilization and circuit complexity. It is concluded that a split-link topology is the best choice compared to a four-leg converter. For the same circuit complexity and dc-bus voltage utilization, the split-link topology results in easier current control and less EMC-problems.