*Article* **Hybrid Multimodule DC-DC Converters for Ultrafast Electric Vehicle Chargers**

#### **Mena ElMenshawy \* and Ahmed Massoud**

Department of Electrical Engineering, Qatar University, Doha 2713, Qatar; Ahmed.massoud@qu.edu.qa **\*** Correspondence: MAlmenshawy@qu.edu.qa

Received: 16 August 2020; Accepted: 15 September 2020; Published: 21 September 2020

**Abstract:** To increase the adoption of electric vehicles (EVs), significant e fforts in terms of reducing the charging time are required. Consequently, ultrafast charging (UFC) stations require extensive investigation, particularly considering their higher power level requirements. Accordingly, this paper introduces a hybrid multimodule DC-DC converter-based dual-active bridge (DAB) topology for EV-UFC to achieve high-e fficiency and high-power density. The hybrid concept is achieved through employing two di fferent groups of multimodule converters. The first is designed to be in charge of a high fraction of the total required power, operating at a relatively low switching frequency, while the second is designed for a small fraction of the total power, operating at a relatively high switching frequency. To support the power converter controller design, a generalized small-signal model for the hybrid converter is studied. Also, cross feedback output current sharing (CFOCS) control for the hybrid input-series output-parallel (ISOP) converters is examined to ensure uniform power-sharing and ensure the desired fraction of power handled by each multimodule group. The control scheme for a hybrid eight-module ISOP converter of 200 kW is investigated using a reflex charging scheme. The power loss analysis of the hybrid converter is provided and compared to conventional multimodule DC-DC converters. It has been shown that the presented converter can achieve both high e fficiency (99.6%) and high power density (10.3 kW/L), compromising between the two other conventional converters. Simulation results are provided using the MatLab/Simulink software to elucidate the presented concept considering parameter mismatches.

**Keywords:** ultra-fast chargers; input-series input-parallel output-series output-parallel multimodule converter; cross feedback output current sharing; reflex charging
