Novel Topology of Three-Phase Electric Spring and Its Control

A novel topology is proposed for three-phase electric spring (TPES) to achieve specific functionalities. With respect to the existing one, the novel topology contains an additional three-phase transformer with the primaries located at the position of the non-critical three-phase load (NCL) of the existing topology and its secondaries connected to the new three-phase NCL, thus forming a new three-phase smart load (SL). To control the novel topology, the so-called modified δ control utilized for the single-phase electric springs is extended to the three-phase case. Thanks to these solutions, TPES exhibits a behavior entirely different from the existing ones. For instance, under a fluctuation of the line voltages, it exhibits a change of the voltages across NCL that has the same trend as the line voltages. Moreover, it regulates the voltages across the three-phase critical load even under both imbalanced and distorted grid conditions. The effectiveness of the novel TPES topology and of its control is validated by simulation results.