To enhance the utilization of ultracapacitor (UC) energy in a battery-UC based hybrid energy storage system (HESS) for electrified vehicle (EV) powertrains, the UC needs to be discharged down to its minimum operating terminal voltage. However, this leads to higher duty cycle operation of the power converter and excessive current at source side. Such conditions hamper the steady operation of the converter and necessitates high current rated magnetic and switching components. Addressing to this challenge, an improved flexible bidirectional multiport converter is proposed, which enables deep discharging of UC without increasing the operating duty cycle or the component ratings of converter, while ensuring flexible power flow among multiple ports. The proposed converter offers the unique feature of energizing the inductor co-operatively through both UC and battery in the same switching cycle, during certain transient events of peak power delivery or regenerative braking energy recuperation. This eventually facilitates in extending the range of UC operation, thereby augmenting the dynamic performance of EV. The flexible operation of the proposed converter along with extended utilization of UC is validated at standard EV load profiles through simulation and further verified by experimentation performed on a laboratory scale hardware prototype.

To overcome the delayed dynamic response of fuel cell (FC), generally battery and ultracapacitor (UC) are preferred to be integrated in a fuel cell electric vehicle (FCEV) powertrain. However, to achieve improved power diversification among multiple energy sources of contrasting power & energy characteristics, independent regulation of each energy source becomes challenging. Aiming at this, an ultra flexible quad-port converter (UFQC), comprising of three input ports and one output port is proposed in this work. The proposed UFQC is capable of providing high flexibility in dynamic power flow management among the three energy sources, catering to diverse range of load power events encountered in a FCEV. Moreover, the UFQC exhibits the feature of charging both battery and UC from the FC and charging of UC from battery. Furthermore, the converter ensures single stage power processing across all power flow scenarios with the ability of simultaneous power transfer between multiple ports. All these features are attained by utilizing only two inductors and three high frequency switches, resulting in judicious utilization of magnetics with simplified gate driving. The flexible operation of UFQC across dynamic power flow scenarios is validated through simulation and preliminary experimentation performed in a laboratory scale hardware prototype.

To augment the power management among battery and ultracapacitor (UC) in a hybrid energy storage system (HESS) for electrified vehicles (EVs), a multiport converter having flexibility in power transfer is desirable. With this objective, a bidirectional dual input single output multiport converter is proposed, which can achieve dynamic flexibility of power flow by employing only two high frequency (HF) switches. The converter comprises a pair of dedicated current flow paths to process high and low level of currents. The current flow paths can be flexibly re-allocated with the desired energy storage depending upon the dynamic load power scenarios of an EV. This enables in maneuvering the flow of power between the three ports according to the nature of variations in an EV load profile. Furthermore, the converter ensures single stage power processing in every possible power flow direction while providing independent control over each power flow path. All these features are obtained by utilizing only two HF switches, thereby demonstrating judicious sharing of components with simplified gate driving and control. The performance of the proposed multiport converter corresponding to dynamic EV load profiles is validated through simulation in MATLAB/Simulink and experimentation on a 1 kW laboratory scale hardware prototype.

To improve the dynamic response of a polymer electrolyte membrane fuel cell (PEMFC), generally battery is preferred to be integrated in a fuel cell hybrid electric vehicle (FCHEV) powertrain. However, the wide terminal voltage of a PEMFC necessitates the use of a DC-DC converter with both step up (boost) and step down (buck) capability to regulate the power flow into the DC bus of a FCHEV powertrain. Aiming at this, a cascaded boost-buck converter (CBBC) with reduced capacitor rating having the ability to handle wide variations of PEMFC voltage is proposed in this work. Further, a modified modulation scheme is proposed, wherein anti-symmetrical carrier signals are provided for boost and buck stages of CBBC. This eventually facilitates in reduction of the RMS value of capacitor ripple current thereby minimizing the size of link capacitor. Analysis of direct and indirect energy transfer between the cascaded boost and buck stages is also carried out to evaluate the performance of modified modulation scheme in comparison with conventional modulation scheme. Furthermore, steady state analysis of CBBC in conjunction with modified modulation scheme is performed through simulation in MATLAB/Simulink platform and also through experimentation in a 5 kW laboratory scale hardware prototype.

In electric vehicles (EVs), the integration of multiple energy storages (MES) is preferred to be a practical solution for improving the performance and lifetime of battery under dynamic driving conditions. At present, most of the commercialized EVs utilize battery as single energy storage to meet the desired driving range. Extended travel range beyond 500 km requires a higher battery capacity with prolonged charging time, which increases the EV production cost. However, this trend is expected to change in the future by integration of MES, particularly a combination like battery + ultracapacitor, fuel cell + battery, fuel cell + ultracapacitor and fuel cell + battery + ultracapacitor. To understand the working mechanism of MES, a technical review on features, benefits and operational characteristics of different energy storages for EVs is discussed. The current framework of the chapter is to provide a preliminary conceptualization on the integration of MES and in-depth technical information on various configurations of multiport DC-DC converter for EV powertrain. In addition, to provide insightful information on MES in EV application, a new flexible bidirectional multiport converter is discussed and its performance results are verified through simulation. Furthermore, current challenges in market adoption and next-generation design considerations of multiport converters in the context of future research prospects are indicated.

To enhance the utilization of the ultracapacitor (UC) energy in a battery-UC based hybrid energy storage system (HESS) for electrified vehicles (EVs), the UC needs to be discharged up to its minimum operating terminal voltage, resulting in higher duty cycle operation of the power converter with excessive high current at source side. This tends to cause instability in the close loop control and necessitates high current rated magnetic and switching components of the converter. Addressing to this, a non-isolated bidirectional multiport converter is proposed, which is capable of ensuring deep discharging of UCs without increasing the operating duty cycle or component ratings of the converter. The proposed converter offers the unique feature of energizing the inductor co-operatively through both UC and battery in the same switching cycle, during certain transient events of peak power delivery or regenerative energy recuperation. This eventually facilitates in extending the range of UC operation, thereby ensuring improved dynamic performance of EV. The operation of the proposed converter is validated through simulation and preliminary experimentation performed in a laboratory scale hardware prototype.

In order to maximize the utilization of battery and ultracapacitor (UC) in a hybrid energy storage system (HESS) for electric vehicle (EV) applications, a DC-DC power electronic interface with proper management of power flow is very crucial. Aiming at this, a non-isolated two input and one output multiport converter configuration, which is capable of achieving dynamic flexibility in power flow while meeting fluctuating load demands of an EV is proposed. The converter provides dedicated power flow paths for high and low currents, which can be flexibly reallocated according to the load current and voltage level of the energy sources. This eventually facilitates in maneuvering the flow of power by dynamically allocating the desired energy source with the appropriate current flow path. Moreover, the proposed converter offers bidirectional power transfer capability for all the ports and allows single stage power conversion in every possible power flow combinations. The converter configuration along with different operating modes and control strategy are discussed and the performance is validated through experimentation using a laboratory scale hardware prototype.

To cater fluctuating load demands in battery operated electric vehicles (EVs), ultracapacitors (UC) are now-a-days being employed as a secondary energy source along with the battery. Considering EVs where size and space of the energy storage system (ESS) is of utmost importance, a modified semi-active configuration for hybridizing lithium ion battery (LiB) with ultracapacitor has been proposed in this work. The hybrid energy storage system (HESS) configuration comprises of a bidirectional dc-dc converter with an effective control scheme to ensure the desired operation of the HESS and also for regulating the power distribution between the LiB and the ultracapacitor module. The performance parameters of the proposed HESS configuration have been evaluated through simulation using MATLAB/Simulink tool and then verified in experimentation using a scaled down bidirectional converter with its control logic validated through dSPACE-1103 controller board.