Implementation of a Two-stage Single-phase Three-wire Power Conversion System

The single-phase three-wire battery energy storage system (BESS) has gained tremendous attention and is progressing toward commercialization. This paper investigates a two-stage single-phase three-wire converter for a single-phase three-wire power distribution system and centers on the coordinated control during grid-connected operation. Along with that, the DC-bus capacitance preference analysis is also conducted using a mathematical model for pulsating power. In this study, the post-stage single-phase three-wire DC/AC converter is used to maintain a constant DC-bus voltage, whereas the active power balancing among single-phase power sources is achieved by an active current sharing approach. On the other hand, the pre-stage DC/DC converter is responsible for the charge and discharge of the battery where the low-frequency current fluctuation can be damped by adding a resonant controller on the existing control scheme. Finally, a 3kW experimental setup is prototyped with the aid of the real-time digital simulation system (RTDS) to verify the rationality and effectiveness of the proposed control strategy.