Systems and methods of this disclosure use low voltage energy storage devices to supply power at a medium voltage from an uninterruptible power supply (UPS) to a data center load. The UPS includes a low voltage energy storage device (ultracapacitor/battery), a high frequency (HF) bidirectional DC-DC converter, and a multi-level (ML) inverter. The HF DC-DC converter uses a plurality of HF planar transformers, multiple H-bridge circuits, and gate drivers for driving IGBT devices to generate a medium DC voltage from the ultracapacitor/battery energy storage. The gate drivers are controlled by a zero voltage switching (ZVS) controller, which introduces a phase shift between the voltage on the primary and secondary sides of the transformers. When the primary side leads the secondary side, the ultracapacitor/battery discharges and causes the UPS to supply power to the data center, and when the secondary side leads the primary side, power flows from the grid back to the UPS, thereby recharging the ultracapacitor/battery.