This paper presents a modular push-pull PWM converter (MPC) for a battery energy storage system, which is intended for grid connections to medium-voltage or high-voltage power systems. The converter per phase consists of a center-tapped transformer and two arms consisting of a cascade connection of multiple bidirectional PWM chopper-cells with floating dc capacitors. This paper discusses the operating performance and control method of the MPC, focusing on voltage balancing of all the floating capacitors. Moreover, a comparison is made between the MPC and a modular multilevel cascade converter (MMCC-DSCC), both of which are used as the same battery energy storage system. The validity of the operating performance and control method is confirmed by both computer simulation using the “PSCAD/EMTDC” software package and experiment using a three-phase, 200-V, and 5-kW downscaled model.