Concurrent Voltage Control and Dispatch of Active Distribution Networks by Means of Smart Transformer and Storage

Dispatching active distribution networks is expected to play an important role in the smart grid technologies. Voltage control is also starting to be widely proposed to avoid voltage violations in the electrical grid. The integration of the storage in the so-called smart transformer (ST), which is a solid-state transformer with control and communication functionalities, can help combine both services. The added value of such a configuration is that it allows the full decoupling of the reactive power flows between the medium voltage (MV) and low voltage (LV) networks. We show the augmented flexibility of such a configuration by proposing a control strategy where the storage system is used to achieve dispatched-by-design operation of the LV network active power flow, as well as the two ST power converters to control the voltage in both the MV and LV grid on a best effort basis. The control strategy is validated by simulations using the IEEE 34 nodes MV test feeder and the CIGRE LV reference network. Moreover, control performance is benchmarked against a conventional network setup, where the battery energy storage system (BESS) is connected to the LV network through a dc/ac power converter and the ST transformer is replaced by a conventional transformer.