A COMPUTATIONALLY EFFICIENT ENERGY MANAGEMENT STRATEGY FOR A PLUG-IN FUEL-CELL HYBRID ELECTRIC VEHICLE COMPOSED OF A MULTI-INPUT CONVERTER

Mugla Journal of Science and Technology A COMPUTATIONALLY EFFICIENT ENERGY MANAGEMENT STRATEGY FOR A PLUG-IN FUEL-CELL HYBRID ELECTRIC VEHICLE COMPOSED OF A MULTIINPUT CONVERTER *Furkan AKAR Electrical and Electronics Engineering Department, Technology Faculty, Duzce University, Turkey, ://orcid.org/0000-0002-1460-4468 Received: 15.10.2018, Accepted: 08.03.2019 *Corresponding author Research Article DOI: 10.22531/muglajsci. 482934 Abstract Fuel cell vehicle technology has drawn wide attention because of the environmental and economic issues related to excessive usage of fossil fuels. Fuel cells are known for their unidirectional environmental friendly operation; however, they have low power density and suffer from slow dynamics. Therefore, a sole fuel cell system cannot meet the requirements of an electric vehicle whose power demand is quite dynamic. In a way of hybridizing a fuel cell with energy storage devices, it can be possible to overcome aforementioned problems. A plug-in fuel cell hybrid electric vehicle system, equipped with a battery and an ultra-capacitor, is proposed in this work. In this system, a single multi-input converter is utilized to control source energies. Moreover, this work develops a computationally efficient energy management strategy which is essentially a frequency decoupling method basically taking the advantage of easily applicable low pass filters. In this strategy, a polynomial scales the fuel cell and battery power levels to regulate ultra-capacitor voltage. The whole system is tested via a simulation model after the detailed analysis of the multi-input converter. Keywords: Fuel cell, battery, ultra-capacitor, electric vehicles, multi-input converter, energy management. ÇOK GİRİŞLİ DÖNÜŞTÜRÜCÜDEN OLUŞAN ŞARJ EDİLEBİLİR YAKIT HÜCRELİ BİR HİBRİT ELEKTRİKLİ ARAÇ İÇİN HESAPLAYICI VERİMLİ BİR ENERJİ YÖNETİM YÖNTEMİ Özet Fosil yakıtların aşırı kullanımının oluşturduğu çevresel ve ekonomik kaygılardan dolayı, yakıt hücreli araç teknolojisi oldukça ilgi çekmektedir. Yakıt hücresi sistemleri tek yönlü çevre dostu işletimleriyle bilinmektedir, ancak güç yoğunlukları düşük ve tepki süreleri yavaştır. Dolayısıyla, bir yakıt hücresi sistemi, güç talebi oldukça dinamik olan bir elektrikli aracın ihtiyacına tek başına cevap verememektedir Yakıt hücresi sistemlerini enerji depolama sistemleri ile birlikte kullanarak bahsedilen problemlerin üstesinden gelinebilir. Bu çalışmada batarya ve ultra-kapasitör içeren şarj edilebilir yakıt hücreli bir hibrit elektrikli araç sistemi sunulmaktadır. Bu sistemde, bir adet çok-girişli dönüştürücü kullanılarak kaynak enerjileri kontrol edilmektedir. Ayrıca, bu çalışma hesaplayıcı verimli bir enerji yönetim stratejisi geliştirmektedir. Temelde bu strateji kolay uygulanabilen alçak geçiren filtrelerden yararlanan bir frekans ayırma yöntemidir. Bu stratejide, bir polinom yakıt hücresi ve batarya güçlerini ölçeklendirerek ultra-kapasitör gerilimini regüle etmektedir. Tüm sistemin çalışması, çok girişli dönüştürücün detaylı analizinden sonra, bir benzetim çalışması ile test edilmektedir. Anahtar Kelimeler: Yakıt hücresi, batarya, ultra-kapasitör, elektrikli araçlar, çok-girişli dönüştürücü, enerji yönetimi. Cite Akar, F., (2019). “A computationally efficient energy management strategy for a plug-in fuel-cell hybrid electric vehicle composed of a multi-input converter”, Mugla Journal of Science and Technology, 5(1), 52-60. (EMS). One of the methods offered in the literature for HPSs is to connect some sources directly to the dc bus while controlling other source energies by bidirectional or unidirectional dc-dc converters [4, 5]. Even though these kinds of semi-active structures are simple and efficient, they do not allow to adjust dc bus voltage and source power levels effectively In addition, works in [6, 7] propose separate converters for each source in order to overcome the issues associated with the semi-active structures at the expense of increased cost and complexity. The other method benefits 1. Introduction Plug-in fuel-cell hybrid electric vehicles (PFCHEVs) come to forefront among EVs; since they offer many advantages; such as, long travel distance, fast charge, high energy/power density, etc [1]-[3]. A PFCHEV includes a hybrid power system (HPS) gathering a fuel-cell (FC) with an energy storage system (ESS) to promote FC lifetime, to increase power density and to allow fuel economy [3]. Source energies in HPSs are controlled via power electronics structures according to an energy management strategy 52 Furkan Akar A Computationally Efficient Energy Management Strategy for a Plug-In Fuel-Cell Hybrid Electric Vehicle Composed of a Multi-Input Converter inverter transfers the regenerative braking energy from the motor when EV is decelerating; UC stores this energy as shown in Fig.1 (b). Here, the battery is not charged though it is possible since it is addressed in [12] that frequent charges can shorten the battery lifetime. from the multi-input converters (MICs), which have several advantages over multiple converter approach; e.g. compact design, low component count, and high energy density [8, 9]. There are two popular structures in the literature for a PFCHEV: FC/ultra-capacitor (UC) and FC/battery/UC. In [6], it is showed that FC/battery/UC system is preferable to FC/UC system when considering many parameters; such as, system size, fuel economy, and battery life time. The proposed FC/battery/UC system in [10] is basically a semi-active topology in which two separate dc-dc converters are used for FC and battery while UC is directly linked to the dc bus. Moreover, [11] offers a similar semi-active system for a FC electric bus in a way of connecting battery to the dc bus directly and utilizing two different dc-dc converters for FC and UC. Furthermore, authors create an active FC/battery/UC hybrid EV in [12] through three separate converters. The studies in [13] and [14] propose FC/battery/UC drivetrains based on a power electronic structure called multiple-input power electronic converter which essentially consists of three bi-directional step-up/stepdown dc-dc converter connected in parallel. Moreover, [15] proposes a three-input dc-dc converter which can effectively build an active FC/battery/UC hybrid system; however, it has only boost capability when powering the output. Additionally, the converter in [15] does not have a common ground that can result in electromagnetic inference (EMI) noise. Unlike the previous studies explored above, an active FC/battery/UC hybrid system is created in this work based on a single MIC which has a common ground as well as buck and boost capabilities. Moreover, this paper offers a new computationally efficient EMS whose details can be found in Section 3. The MIC used in this work is shown in Fig. 1(a). This MIC is evaluated in [16] when it has 2 inputs. Moreover, 3input case is studied in [17] via an ideal switching model. Although demonstrated simulation results i (...truncated)