Multi-module parallel small battery energy storage system

This paper presents a multi-module parallel single-phase battery energy storage system (BESS). The single module BESS to be paralleled consists of only a full-bridge power converter. When the utility is in normal condition, the BESS serves as a power conditioner as well as an active power filter. It can be arranged to charge the battery bank or to share daily peak load. In any case, the current supplied by the electric utility can be maintained sinusoidal and almost in phase with voltage. When a utility power failure occurs, the BESS functions as an inverter to supply uninterruptible power to the load. With the good current sharing feature possessed by this BESS, a central power distribution control scheme with smooth current transfer characteristic is proposed to control the parallel operation of the multi-module BESS. The current sharing of each BESS module can be programmed according to its rating and the load condition. Designs of the power circuit and the central power distribution control scheme are described detailedly in this paper. The effectiveness and performance of the proposed parallel BESS are demonstrated by some experimental results.