Bidirectional DC-DC Resonant Converter Design for Electric Vehicle Charging Stations Integration to MVDC Grids

The extensive use of electric vehicles (EVs) needs ultra-fast-charging stations with high charging power greater than 22 kW (P_Charging >22kW). Medium voltage direct current (MVDC) grids can provide the best solution for the high demand of EVs and fast-charging stations infrastructures with the existing distribution grids. The resonant bidirectional dual active bridge (DAB) DC-DC converter can be a promising technology in integrating an electric vehicle charging station (EVCS) with MVDC grid. This work focuses on the converter design with voltage control and stability by applying two different control strategies mainly: PI control and sliding mode control (SMC). All simulations will be performed in order to present the feasibility of the proposed solution and compare the results of each control methods. This comparison, for the first time, in the medium voltage level can open new insights for using nonlinear control methods such as SMC to ensure stability and obtain better dynamic performance.

I. Introduction

With the widespread using of electric vehicles (EVs), charging time reduction is the main challenge. The level 3 of fast charging can reduce the charging time to less than 15 minutes with the power rating in the range of 50-350 kW [1]-[2]. In the near future, the power demand for feeding these EVs may exceed the capacity of existed grids since the charging power depends on the capacity of electric cars that tends to be 60 kWh. Thus, Ultra-fast charging stations with charging power greater than 22 kW (PCharging >22kW) that can use MVDC grids are considered as an optimal solution to supply charging loads [3].