Independent Per-Phase Power Control in Four-Leg Grid-Following Voltage Source Converters

Distribution grids are facing a great transformation in recent years with the advent of smart grid technologies. Particularly, more and more controllable devices, based on power electronics, are being deployed in this part of the power system. These interfacing devices are in charge of the active power management of many energy resources ranging from renewable energy sources to energy storage systems. However, in addition to this, power electronics may provide valuable ancillary services for improving the operation of distribution networks. With this regard, it is important to stress that low-voltage distribution systems are by nature unbalanced due to single-phase loads. Therefore, the use of already installed voltage source converters for minimizing the network imbalance could be of interest to the Distribution System Operator. This paper proposes a per-phase independent power control of three-phase four-leg Voltage Source Converters for reducing network voltage imbalance. The control approach has been experimentally validated in a test bed to evidence the technical feasibility of the proposal.