Ancillary Services of A Triple-Port Smart Transformer

Abstract

Smart transformers have recently gained considerable attention for their ability to provide essential ancillary services to the power grid, such as voltage regulation, frequency support, reactive power compensation, and renewable energy integration. In this paper, a triple-port smart transformer based on a triple active bridge (TAB) topology is proposed to interface a photovoltaic (PV) system, a battery energy storage system (BESS), and local AC loads. The TAB topology enables flexible and bidirectional power flow control among the three ports. Ancillary services supported by the system include voltage regulation and soft load reduction, where load power is reduced by intentionally lowering the supply voltage rather than disconnecting loads. The effect of load-side voltage variations on the controllability of power flow is analyzed, and based on this analysis, a decoupled controller is designed to enhance system performance. Comprehensive simulations are carried out using MATLAB/Simulink to validate the system architecture and control approach. Additionally, a scaled-down hardware prototype is developed to experimentally verify the proposed concept.