A Comprehensive Analysis and Control Strategy for Nullifying Negative- and Zero-Sequence Currents in an Unbalanced Three-Phase Power System Using Electric Springs

This paper presents a general analysis and a control strategy that enables electric springs (ES) to mitigate the negative-sequence and zero-sequence currents in unbalanced three-phase power systems. The analysis indicates that under certain load conditions, power balance can be restored without the need for active power from the ES. Outside such conditions, the theory can pinpoint the precise operating point at which power balance can be achieved with the minimum active power from the ES. Thus, the optimum use of energy usage and battery size for providing/storing active power can be realized. Simulation and experiment results obtained from a 3-kW hardware setup have verified the new theory and the control method.