Grid integration of DC fast‐charging stations for EVs by using modular li‐ion batteries

Abstract

Widespread use of electric vehicles (EVs) requires investigating impacts of vehicles' charging on power systems. This paper focuses on the design of a new DC fast charging station (DCFCS) for EVs combined with local battery energy storages (BESs). Due to the BESs the DCFCS is able to decouple the peak load demand caused by multiple EVs and decrease the installation costs as well as the connection fees. The charging system is equipped with a bidirectional AC/DC converter, two lithium-ion batteries and a DC/DC converter. The introduction of BES within the DCFCSs is investigated with regards to operational costs of the charging stations as well as the ability of a BES to mitigating negative impacts on the power grid during congestion hours. The proposed solution is shown to reduce not only the installation costs but also the charging time and it facilitates the integration of fast chargers in existing low voltage (LV) grids. A cost-benefit analysis (CBA) is performed to evaluate the financial feasibility of BES within the DCFCSs by considering the installation costs, grid connection costs and battery life cycle costs. E IntroductionINCREASED focus on sustainable transportation and CO2 reduction leads to large investments into electric vehicle (EV) technology from the major car producers. Rising numbers of EVs in major cities and widespread rollout of EV charging infrastructures are introducing new high power loads to distribution system operators (DSOs). In recent years environmental concerns and advances in battery technology drive the rapid development of electrical transportation [1]- [3]. In a sustainable city [4], with an increasing amount of electric vehicles, a lot of concern is raised on EV grid integration as well as a tariff system that allows to control the EVs charging demand [5]- [6]. The EN /IEC 61815 and automotive engineers in U.S. SAE J1772 have proposed the EV charging modes and the maximum current delivered both on alternating and direct current (AC and DC).Currently, the public charging stations in the major European cities are providing 7 -43 kW [7], which with the current EV models and charging stations require more than an hour to cover a range of 150 km.Considering the growing number of EVs over the next 10 years [8], appropriate fast charging infrastructures are anticipated to supply the future EV power demand. Therefore, the widespread use of EVs requires investigating impacts of vehicles' charging on the distribution grids. So far, extensive study has focused on optimizing the EV penetration and the charging infrastructure. An optimal approach is proposed in [9] with a day-ahead energy planning of EVs by scheduling

System Planning of Grid-Connected Electric Vehicle Charging Stations and Key Technologies: A Review

“…Popular technical topics discussed in this category include quantitative analysis in various system designs, system configuration planning, modeling, control, and hybrid ESS (HESS) design for applications in ECSs [43]. In [44][45][46][47][48][49][50][51][52][53], the design and configuration of ECSs were discussed. M. Vasiladiotis and A. Rufer [44] proposed a modular multiport power electronic transformer based on a delta-connected cascaded H-bridge converter to incorporate a split-battery ESS for ultrafast EV charging service.…”

“…V. Salapić et al [51] proposed a mixed integer linear programming (MILP) scheme for the optimal capacity and control of an ESS. In [52], a new FCS with modular lithium-ion batteries was designed for an existing low-voltage grid with a reduced cost and charging time. The application and stochastic modeling-based capacity planning of batteries in FCSs was explored in [53] to optimize charging service.…”

Fast charging converter and control algorithm for solar PV battery and electrical grid integrated electric vehicle charging station

“…So, battery EVs and plugged-in hybrid EVs are gaining wide attention [1]. The move from internal combustion engine vehicles to electric vehicle will happen soon and more rapidly than the expectation, but the major barriers for EV commercialization are; size of the battery, time taken to recharge, inefficient power conversion due to multiple stages and grid instability during peak hours due to increased power consumption [2]. A hybrid charging station which is less grid-dependent, can overcome the above barriers.…”

“…An SPV-EVCS with battery backup has two types of architecture (1) Common AC bus architecture, (2) Common DC bus architecture and it is represented in Figure 1(a,b) [4,5].…”

A novel structure for high step‐up DC‐DC converter with flexibility under the variable loads for EV solar charging system

“…Overloading from fast‐charging stations imposes an additional burden on the power grid, voltage instability, and reliability problems. It also influences various parameters of distribution networks such as voltage profile, harmonic distortions, and peak load characteristics …”