Optimal design of DC fast-charging stations for EVs in low voltage grids

Abstract

Abstract-DC Fast Charging Station (DCFCS) is essential for widespread use of Electric Vehicle (EVs). It can recharge EVs in direct current in a short period of time. In recent years, the increasing penetration of EVs and their charging systems are going through a series of changes. This paper addresses the design of a new DCFCS for EVs coupled with a local Battery Energy Storage (BES). DCFCS is equipped with a bidirectional AC/DC converter for feeding power back to the grid, two lithium batteries and a DC/DC converter. This paper proposes an optimal size of the BES to reduce the negative impacts on the power grid through the application of electrical storage systems within the DC fast charging stations. The proposed solution decreases the charging time and the impact on the low voltage (LV) grid significantly. The charger can be used as a multifunctional grid-utility such as congestion management and load levelling. Finally, an optimal design of the DCFSC has been done to evaluate the feasibility and the operability of the system in different EVs load conditions.

Cost-benefit analysis of a novel DC fast-charging station with a local battery storage for EVs

“…The new design of the charging stations is based on the installation of two identical battery energy system (BES1 and BES2) that physically decouples a DC fast charging station (DCFCS) from an LV distribution grid, as shown in Figure 1. The operation of such a system is based on successive switches of the BES connections that allow one of the batteries (BES2) to be charged from the grid while the other (BES1) is charging an EV and vice versa [10]- [11]. The case study uses an AC/DC converter of 100kW and charging rate of 6C (9.7min) [11].…”

“…The operation of such a system is based on successive switches of the BES connections that allow one of the batteries (BES2) to be charged from the grid while the other (BES1) is charging an EV and vice versa [10]- [11]. The case study uses an AC/DC converter of 100kW and charging rate of 6C (9.7min) [11]. The discharging rate through the DC/DC is 9C (6.7min) with a converter of 150kW.…”

“…To satisfy the energy demand from EVs, the optimal BES for a DCFCS is 16kWh because it meets the highest level of SoCs satisfaction. It means more than 80% of the commercial EV can be charged up to their 80% of SoC [11]. Each BES has been oversized of 19 This case study takes into account the maximum power of the LV grids in order to prevent the connection in MV.…”

“…Designing an appropriate DC-charging station in low voltage (LV) is important to avoid the connection in MV and minimize the operating costs [10]- [11]. In addition, distribution system operators (DSOs) are focused on minimizing losses and reducing the size of the electrical lines to mitigate the network congestion [12]- [13].…”

Estação de Carregamento Rápido com Elemento Armazenador de Energia e Filtro Ativo de Harmônicos para Veículos Elétricos

“…O nível 3 de carregamento, foco deste trabalho, é realizado em 50 kW a 120 kW, com conversor off-board, o qual fornece energia em corrente contínua (CC) durante 10 a 30 min. O tempo de carregamento depende da potência máxima da estação, do nível de carga e da capacidade da bateria [5], [13], [14]. O nível 3 é também conhecido por carregamento rápido CC.…”