Voltage balancing in low-voltage radial feeders using Scott transformers

Abstract

Increasing use of heat pumps, micro-generation, electric vehicles and energy-saving technologies is expected to cause severe voltage imbalance on low-voltage (LV) radial feeders and deteriorate the power quality seen by single-phase (1Φ) and three-phase (3Φ) LV connected consumers. To solve this problem, a Scott transformer-based balancing technique is used to convert an unbalanced 3Φ supply into a balanced 3Φ supply at either one point on an LV radial feeder or a 3Φ load supply point. Moreover, by replacing the traditional methods of increasing LV cable cross-sections to solve voltage imbalance; or future solutions such as automatic network reconfiguration, the economic cost of operating and upgrading a 'stressed' LV feeder can be minimised. A computer simulation study, in which the proposed method is used to balance a typical UK LV network, with varying levels of imbalance, was carried out. Furthermore, a 'small-scale' physical voltage balancing system based on the proposed method was constructed and tested in the laboratory. The results obtained from various simulation and experimental scenarios demonstrated that the proposed method can continuously maintain a balanced 3Φ supply by compensating for phase-related voltage dips and surges resulting from variations in 1Φ connected loads.