A hierarchical energy management strategy for fuel cell/battery/supercapacitor hybrid electric vehicles

In this paper, a hierarchical energy management strategy (EMS) based on low-pass filter and equivalent consumption minimization strategy (ECMS) is proposed in order to lift energy sources lifespan, power performance and fuel economy for hybrid electrical vehicles equipped with fuel cell, battery and supercapacitor. As for the considered powertrain configuration, fuel cell serves as main energy source, and battery and supercapacitor are regarded as energy support and storage system. Supercapacitor with high power density and dynamic response acts during great power fluctuations, which relives stress on fuel cell and battery. Meanwhile, battery is used to lift the economy of hydrogen fuel. In higher layer strategy of the proposed EMS, supercapacitor is employed to supply peak power and recycle braking energy by using the adaptive low-pass filter method. Meantime, an ECMS is designed to allocate power of fuel cell and battery such that fuel cell can work in a high efficient range to minimize hydrogen consumption in lower layer. The proposed EMS for hybrid electrical vehicles is modeled and verified by advisor-simulink and experiment bench. Simulation and experiment results are given to confirm effectiveness of the proposed EMS of this paper.     

Fuel cell/battery passive hybrid power source for electric powertrains

The concept of passive hybrid, i.e. the direct electrical coupling between a fuel cell system and a battery without using a power converter, is presented as a feasible solution for powertrain applications. As there are no DC/DC converters, the passive hybrid is a cheap and simple solution and the power losses in the electronic hardware are eliminated. In such a powertrain topology where the two devices always have the same voltage, the active power sharing between the two energy sources can not be done in the conventional way. As an alternative, control of the fuel cell power by adjusting its operating pressure is elaborated. Only pure H₂/O₂ fuel cell systems are considered in this approach. Simulation and hardware in the loop (HIL) results for the powertrain show that this hybrid power source is able to satisfy the power demand of an electric vehicle while sustaining the battery state of charge.     

Fuzzy neural control of a hybrid fuel cell/battery distributed power generation system

An innovative control strategy is proposed of hybrid distributed generation (HDG) systems, including solid oxide fuel cell (SOFC) as the main energy source and battery energy storage as the auxiliary power source. The overall configuration of the HDG system is given, and dynamic models for the SOFC power plant, battery bank and its power electronic interfacing are briefly described, and controller design methodologies for the power conditioning units and fuel cell to control the power flow from the hybrid power plant to the utility grid are presented. To distribute the power between power sources, the fuzzy switching controller has been developed. Then, a Lyapunov based-neuro fuzzy algorithm is presented for designing the controllers of fuel cell power plant, DC/DC and DC/AC converters; to regulate the input fuel flow and meet a desirable output power demand. Simulation results are given to show the overall system performance including load-following and power management of the system.     

Nonlinear control and optimization of hybrid electrical vehicle under sources limitation constraints

This work presents a new contribution on energy management of hybrid electric systems for vehicle applications. The studied hybrid electrical vehicle is composed of fuel cell as a main source and the auxiliary system containing the battery and supercapacitor. A programmable load is used to emulate a vehicle load profile. Two methods are combined to smartly and optimally control the energy flow between the used sources. These methods are the Interconnection and Damping Assignment Passivity Based Control (IDA-PBC) and the Hamilton-Jacobi Bellman (HJB) optimization. The source limitation is considered here in terms of the battery state of charge. The experimental works validate the efficiency of the proposed control where the obtained results demonstrate that the used strategy allows regulating the power flow under a realistic load drive profile. The global stability proof is demonstrated using Lyapunov theory.     

Energy management of PEM fuel cell/ supercapacitor hybrid power sources for an electric vehicle

This paper presents the utilization of a supercapacitor (SC) as an auxiliary power source in an electric vehicle (EV), composed of a proton electrolyte membrane fuel cell (PEMFC) as the main energy source. The main weak point of PEMFC is slow dynamics because one must limit the fuel cell current slope in order to prevent fuel starvation problems, to improve its performance and lifetime. The very fast power response and high specific power of a supercapacitor can complement the slower power output of the main source to produce the compatibility and performance characteristics needed in a propulsion system. DC-DC converters connected to the hybrid source ensure a constant voltage value in inverters inputs. After an architecture presentation of the hybrid energy source, two parallel-type configurations are explored in more detail. For each of them, the energy flow control and management, validated simulation shows the performance obtained in this configuration. The hybrid source management is based primarily on the intervention of the supercapacitor in fugitives' schemes such as slopes, different speeds and rapid acceleration. Secondly, the PEMFC intervenes to guarantee the power in permanent regime. Finally, simulation results considering energy management are presented and illustrated the hybrid energy source benefits.     

Power switch failures tolerance and remedial strategies of a 4-leg floating interleaved DC/DC boost converter for photovoltaic/fuel cell applications

In recent years, many researchers have proposed new DC/DC converters in order to meet the fuel cell requirements. The reliability of these DC/DC converters is crucial in order to guarantee the availability of fuel cell systems. In these converters, power switches ranked the most fragile components. In order to enhance the reliability of DC/DC converters, fuel cell systems have to include fault-tolerant topologies. Usually, dynamic redundancy is employed to make a fault-tolerant converter. Despite this kind of converter allows ensuring a continuity of service in case of faults, the use of dynamic redundancy gets back to increase the complexity of the converter. In order to cope with reliability expectations in DC/DC converters, floating interleaved boost converters seem to be the best solution. Indeed, they have much to offer for fuel cells and DC renewable energy sources (i.e. photovoltaic system), including reduced input current ripple and reliability in case of faults. Despite the offered benefits of this topology, operating degraded modes lead up to undesirable effects such as electrical overstress on components and input current ripple increasing. The aim of this paper is to carry out a thorough analysis of these undesirable effects and to propose remedial strategies to minimize them.     

An utility interactive power electronics interface foralternate/renewable energy systems

The foreseeable shortages in conventional sources of electric power has increased the emphasis on the research and development of alternate sources of energy. In order to make a noteworthy impact, the alternate sources of energy need to be utility interactive by means of a power electronic interface (a DC to AC converter). The inherent assumption in the control of DC to AC converters is, that the DC voltage available at the input of the converter is constant. However, when the input is an unregulated DC source such as a battery, fuel cell, photovoltaic cells or any other form of alternate source, maintenance of the constant DC voltage at the input of the converter is often impossible. A modified inverter switching technique is proposed for the interface with the utility grid such that the AC output of the inverter becomes immune to fluctuations in the unregulated input DC obtained from alternate energy sources     

Energy management of fuel cell/battery/supercapacitor hybrid power source for vehicle applications

This paper proposes a perfect energy source supplied by a polymer electrolyte membrane fuel cell (PEMFC) as a main power source and storage devices: battery and supercapacitor, for modern distributed generation system, particularly for future fuel cell vehicle applications. The energy in hybrid system is balanced by the dc bus voltage regulation. A supercapacitor module, as a high dynamic and high power density device, functions for supplying energy to regulate a dc bus voltage. A battery module, as a high energy density device, operates for supplying energy to a supercapacitor bank to keep it charged. A FC, as a slowest dynamic source in this system, functions to supply energy to a battery bank in order to keep it charged. Therefore, there are three voltage control loops: dc bus voltage regulated by a supercapacitor bank, supercapacitor voltage regulated by a battery bank, and battery voltage regulated by a FC. To authenticate the proposed control algorithm, a hardware system in our laboratory is realized by analog circuits and numerical calculation by dSPACE. Experimental results with small-scale devices (a PEMFC: 500-W, 50-A; a battery bank: 68-Ah, 24-V; and a supercapacitor bank: 292-F, 30-V, 500-A) corroborate the excellent control principle during motor drive cycle.     

Optimized power management based on adaptive-PMP algorithm for a stationary PEM fuel cell/battery hybrid system

This research develops an efficient and robust polymer electrolyte membrane (PEM) fuel cell/battery hybrid operating system. The entire system possesses its own rapid dynamic response benefited from hybrid connection and power split characteristics due to DC/DC buck-boost converter. An indispensable energy management system (EMS) plays a significant role in achieving optimal fuel economy and in a promising running stability. EMS as an indispensable part plays a significant role in achieving optimal fuel economy and promising operation stability. This study aims to develop an adaptive supervisory EMS that comprises computer-aided engineering tools to monitor, control, and optimize the performance of the hybrid power system. A stationary fuel cell/battery hybrid operating system is optimized using adaptive-Pontryagin's minimum principle (A-PMP). The proposed algorithm depends on the adaptation of the control parameter (i.e., fuel cell output power) from the state of charge (SOC) and load power feedback. The integrated model simulated in a Matlab/Simulink environment includes the fuel cell, battery, DC/DC converter, and power requirements models by analyzing the three different load profiles. Real-time experiments are performed to verify the effectiveness of EMS after analyzing the simulated operating principle and control scheme.     

Viability study of a FC-battery-SC tramway controlled by equivalent consumption minimization strategy

This paper evaluates the option of using a new powertrain based on fuel cell (FC), battery and supercapacitor (SC) for the Urbos 3 tramway in Zaragoza, Spain. In the proposed powertrain configuration, a hydrogen Proton-Exchange-Membrane (PEM) FC acts as main energy source, and a Li-ion battery and a SC as energy support and storage systems. The battery supports the FC during the starting and accelerations, and furthermore, it absorbs the power generated during the regenerative braking. Otherwise, the SC, which presents the fastest dynamic response, acts mainly during power peaks, which are beyond the operating range of the FC and battery. The FC, battery and SC use a DC/DC converter to connect each energy source to the DC bus and to control the energy exchange. This configuration would allow the tramway to operate in an autonomous way without grid connection. The components of the hybrid tramway, selected from commercially available devices have been modeled in MATLAB-Simulink. The energy management system used for controlling the components of the new hybrid system allows optimizing the fuel consumption (hydrogen) by applying an equivalent consumption minimization strategy. This control system is evaluated by simulations for the real driving cycle of the tramway. The results show that the proposed control system is valid for its application to this hybrid system.     

A fuel-cell/battery hybrid DC backup power system via a new high step-up three port converter

In this paper, a fuel-cell (FC)/battery hybrid direct-current (DC) backup power system is proposed for high step-up applications. This system is composed of a newly developed non-isolated three-port converter, which achieves a high voltage gain by taking the advantage of a quasi Z-source network and an energy transfer capacitor. After analyzing the converter, a comprehensive comparison study and a design procedure are provided. Moreover, the controllers regulating the source power levels while smoothing the FC power profile according to the proposed energy management strategy (EMS) are designed based on the developed small-signal model of the proposed converter. Both hardware and controller design procedures are validated through the PSIM model of the whole system. As a result, it is shown that the proposed system can effectively couple FC and battery while transferring their energies to a high voltage DC bus according to the offered EMS.     

An actively controlled fuel cell/battery hybrid to meet pulsed power demands

This paper presents the experimental results of an actively controlled fuel cell/battery hybrid power source topology that can be widely used in many applications, such as portable electronic devices, communication equipment, spacecraft power systems, and electric vehicles, in which the power demand is impulsive rather than constant. A step-down DC/DC power converter is incorporated to actively control the power flow between the fuel cell and the battery to achieve both high power and high energy densities. The results show that the hybrid power source can achieve much greater specific power and power density than the fuel cell alone. This paper first demonstrates that an actively controlled hybrid with a 35 W hydrogen-fueled polymer electrolyte membrane fuel cell and a lithium-ion battery pack of six cells yielded a peak power of 100 W, about three times as high as the fuel cell alone can supply, while causing a very limited (10%) weight increase to the whole system. After that, another hybrid source using a different battery array (eight cells) was investigated to further validate the control strategy and to show the flexibility and generality of the hybrid source design. The experimental data show that the hybrid source using an eight-cell battery supplied a peak power of 135 W, about four times that of the fuel cell alone. Finally, three power sources including the fuel cell alone and the two hybrids studied were compared in terms of specific power, power density, volume, weight, etc. The design presented here can be scaled to larger or smaller power capacities for a variety of applications.     

DC/DC converter topologies for electrolyzers: State-of-the-art and remaining key issues

In recent years, the use of electrolyzers to produce cleanly and efficiently hydrogen from renewable energy sources (i.e. wind turbines, photovoltaic) has taken advantage of a growing interest from researchers and industrial. Similarly to fuel cells, DC/DC converters are needed to interface the DC bus with the electrolyzer. Usually, electrolyzers require a low DC voltage to produce hydrogen from water. For this reason, a DC/DC buck converter is generally used for this purpose. However, other DC/DC converter topologies can be used depending on the feature of the electrolyzer and electrical grid as well. The main purpose of this paper is to present the current state-of-the-art of DC/DC converter topologies which can be combined with electrolyzers. The different DC/DC converter topologies are compared in terms of output current ripple reduction, conversion ratio, energy efficiency, and power switch fault-tolerance. Besides, remarks on the state-of-the-art and remaining key issues regarding DC/DC converters are provided.     

Development and application of an actively controlled hybrid proton exchange membrane fuel cell—Lithium-ion battery laboratory test-bed based on off-the-shelf components

The use of commercially available components enables rapid prototyping and assembling of laboratory scale hybrid test-bed systems, which can be used to evaluate new hybrid configurations. The development of such a test-bed using an off-the-shelf PEM fuel cell, lithium-ion battery and DC/DC converter is presented here, and its application to a hybrid configuration appropriate for an unmanned underwater vehicle is explored. A control algorithm was implemented to regulate the power share between the fuel cell and the battery with a graphical interface to control, record and analyze the electrochemical and thermal parameters of the system. The results demonstrate the applicability of the test-bed and control algorithm for this application, and provide data on the dynamic electrical and thermal behaviour of the hybrid system.     

System design and control strategy of the vehicles using hydrogen energy

This paper presented a system design review of fuel cell hybrid vehicle. Fuel supply, hydrogen storage, DC/DC converters, fuel cell system and fuel cell hybrid electric vehicle configurations were also reviewed. We explained the difference of fuel supply requirement between hydrogen vehicle and conventional vehicles. Three different types of hydrogen storage system for fuel supply are briefly introduced: high pressure, liquid storage and metal oxides storage. Considering of the potential risk of explosion, a security hydrogen storage system is designed to restrict gas pressure in the safe range. Due to the poor dynamic performance of fuel cells, DC/DC converters were added in hybrid vehicle system to improve response to the changes of power demand. Requirements that in order to select a suitable DC/DC converter for fuel-cell vehicles design were listed. We also discussed three different configurations of fuel-cell hybrid vehicles: “FC + B”, “FC + C”, and “FC + B + C”, describing both disadvantages and advantages. “FC + B + C” structure has a better performance among three structures because it could provide or absorb peak current during acceleration and emergency braking. Finally, the energy management strategies of fuel cell and were proposed and the automotive energy power requirement of an application example was calculated.     

Review on non-isolated multi-input step-up converters for grid-independent hybrid electric vehicles

The increase in temperature, regulations of CO2 emissions, and the cost of conventional fuels forced the transportation industry to move towards the electrical energy sector. The increasing nature of electrification of transportation will increase the stress on the existing power system because of the charging of battery-based electric vehicles (EV). This paper briefly reviews the effect of electrification of transportation on the existing power system. The Lion's share of the EVs is battery-based, and these EVs extensively depend on Lithium. The Lithium is a non-renewable energy source just like fossil fuels, and reserves may last one day. The availability of Lithium reserves across the world and alternate for the grid-dependent EVs are illustrated in this paper. This paper also briefly discusses the fuel cell-based EVs, solar PV based EVs along with battery-based EVs and compare the battery with fuel cell.There is a significant need for research and development on grid-independent hybrid electric vehicles (GIHEV). From the last few years, the extensive part of the hybrid electric vehicles is making use of multi-input DC-DC converters to interface multiple sources to enhance the performance and reliability of the vehicle. Among different types of multi-input DC-DC converters, non-isolated multi-input DC-DC converters are best suited for low and medium power electric vehicle applications. This paper displays the synthesizing process of multi-input converters. Some of the existing efficient non-isolated multi-input high step-up DC-DC converter topologies are immensely discussed and compared. This review is intended to serve as a suitable guideline and reference for future work in the field of non-isolated multi-input high step-up DC-DC converter topologies for GIHEVs.     

A power allocation strategy of a hybrid energy storage system for a PV grid-connected system

针对光伏并网系统中光伏微电源出力的波动性和间歇性,将蓄电池和超级电容器构成的混合储能系统HESS（hybrid energy storage system）应用到光伏并网系统中可以实现光伏功率平滑、能量平衡以及提高并网电能质量。在同时考虑蓄电池的功率上限和超级电容的荷电状态（SOC）的情况下,对混合储能系统提出了基于超级电容SOC的功率分配策略;该策略以超级电容的SOC和功率分配单元的输出功率作为参考值,对混合储能系统充放电过程进行设计。超级电容和蓄电池以Bi-direction DC/DC变换器与500 V直流母线连接,其中超级电容通过双闭环控制策略对直流母线电压进行控制。仿真结果表明,所提功率分配策略能对混合储能系统功率合理分配,而且实现了单位功率因数并网,稳定了直流母线电压。     

Distributed control of a user-on-demand renewable-energy power-source system using battery and hydrogen hybrid energy-storage devices

A user-on-demand power source based on renewable energy requires storage devices to balance power sources and power demands because of the fluctuation of power sources like solar cells or wind power generators. The role of the control system is defined as two different tasks: allowing a power-flow imbalance between demand and power sources; and balancing the power flow inside the system. Since this control is complicated, many control methods using precise calculation of the power balance have been proposed. An analogue-like distributed control method - named “modified DC-bus signalling” - for controlling a renewable-energy power source without the need for a central processing unit is proposed. The modified DC bus signalling method discussed in this paper is composed of a DC-bus line connected with a battery, water-splitting electrochemical cell, and a fuel cell for hydrogen-energy storage via converters. The proposed control method was demonstrated to be able to control step-like and random changes in input and output power. The battery compensated high-frequency fluctuations in power demand, and the electrochemical cell and fuel cell handled the remaining low-frequency ones, which were matched to their response speeds.     

Modeling,control and power management of hybrid photovoltaic fuel cells with battery bank supplying electric vehicle

In this paper, modeling, control and power management (PM) of hybrid Photovoltaic Fuel cell/Battery bank system supplying electric vehicle is presented. The HPS is used to produce energy without interruption. It consists of a photovoltaic generator (PV), a proton exchange membrane fuel cell (PEMFC), and a battery bank supplying an electric vehicle of 3 kW. In our work, PV and PEMFC systems work in parallel via DC/DC converter and the battery bank is used to store the excess of energy. The mathematical model topology and it power management of HPS with battery bank system supplying electric vehicle (EV) are the significant contribution of this paper. Obtained results under Matlab/Simulink and some experimental ones are presented and discussed.     

Improved fuzzy logic control-based energy management strategy for hybrid power system of FC/PV/battery/SC on tourist ship

An improved fuzzy-based energy management strategy (EMS) is proposed for a tourist ship used hybrid power system with multiple power sources consisting of fuel cell(FC)/photovoltaic cell(PV)/battery(BAT)/super-capacitor(SC). The power demand from propeller and user terminal is afforded by the power sources connecting to power converters. To obtain more superior performance of the power system, the maximum power point tracking (MPPT) algorithm is employed to optimize the PV. Meanwhile, the improved fuzzy logic control based on dynamic programming (DP) associated with wavelet analysis and PI control are employed to achieve the output power optimal distribution and online control. In particular, the MPPT algorithm can improve the utilization of solar energy, and the SC can well absorb the high frequency power and reduce the fluctuation of the battery and FC that exhibits the potential of their lifetime extension. The FC outputs the high and stable power satisfying the ship's power demand even under the extreme work conditions. The developed model is able to illustrate well in the operation process of the hybrid power system governed by the proposed EMS. In addition, compared with the rule-based strategy, the improved fuzzy-based EMS can reduce 14.39% hydrogen consumption and keep the consistency of battery SOC.