An innovative optimal power allocation strategy for fuel cell, battery and supercapacitor hybrid electric vehicle

An optimal design of a three-component hybrid fuel cell electric vehicle comprised of fuel cells, battery, and supercapacitors is presented. First, the benefits of using this hybrid combination are analyzed, and then the article describes an active power-flow control strategy from each energy source based on optimal control theory to meet the demand of different vehicle loads while optimizing total energy cost, battery life and other possible objectives at the same time. A cost function that minimizes the square error between the desired variable settings and the current sensed values is developed. A gain sequence developed compels the choice of power drawn from all devices to follow an optimal path, which makes trade-offs among different targets and minimizes the total energy spent. A new method is introduced to make the global optimization into a real-time based control. A model is also presented to simulate the individual energy storage systems and compare this invention to existing control strategies, the simulation results show that the total energy spent is well saved over the long driving cycles, also the fuel cell and batteries are kept operating in a healthy way.     

Energy control of supercapacitor/fuel cell hybrid power source

This paper deals with a flatness based control principle in a hybrid system utilizing a fuel cell as a main power source and a supercapacitor as an auxiliary power source. The control strategy is based on regulation of the dc bus capacitor energy and, consequently, voltage regulation. The proposed control algorithm does not use a commutation algorithm when the operating mode changes with the load power variation and, thus, avoids chattering effects. Using the flatness based control method, the fuel cell dynamic and its delivered power is perfectly controlled, and the fuel cell can operate in a safe condition. In the hybrid system, the supercapacitor functions during transient energy delivery or during energy recovery situations. To validate the proposed method, the control algorithms are executed in dSPACE hardware, while analogical current loops regulators are employed in the experimental environment. The experimental results prove the validity of the proposed approach.     

Energy management of a fuel cell hybrid ultra-energy efficient vehicle

This paper focuses on energy management in an ultra-energy efficient vehicle powered by a hydrogen fuel cell with rated power of 1 kW. The vehicle is especially developed for the student competition Shell Eco-marathon in the Urban Concept category. In order to minimize the driving energy consumption a simulation model of the vehicle and the electric propulsion is developed. The model is based on vehicle dynamics and real motor efficiency as constant DC/DC, motor controllers and transmission efficiency were considered. Based on that model five propulsion schemes and driving strategies were evaluated. The fuel cell output parameters were experimentally determined. Then, the driving energy demand and hydrogen consumption was estimated for each of the propulsion schemes. Finally, an experimental study on fuel cell output power and hydrogen consumption was conducted for two propulsion schemes in case of hybrid and non-hybrid power source. In the hybrid propulsion scheme, supercapacitors were used as energy storage as they were charged from the fuel cell with constant current of 10 A.     

Experimental assessment of fuel cell/supercapacitor hybrid system for scooters

This paper presents an experimental assessment of fuel cell hybrid propulsion systems for scooters based on a modular 1.2 kW PEM fuel cell. The tests of the hybrid system are carried out using a programmable electronic load. Different configurations of the fuel cell/battery and the fuel cell/supercapacitor hybrid systems are explored. Both systems demonstrate their ability to deliver the requested load satisfactorily. The distributions of the fuel cell power delivery, although different between the two systems, are within the region where the fuel cell efficiency is approximately constant. As a result, the rates of fuel consumption show no discernable difference between the two systems for all three driving cycles considered. In addition to the fuel consumption, considerations including bus voltage, cost and packaging issues suggest that the supercapacitor has advantages over the battery for the use as secondary energy storage in fuel cell hybrid propulsion system for scooters.     

Integration of fuel cells and supercapacitors in electrical microgrids: Analysis,modelling and experimental validation

This article examines a hybrid storage system comprising fuel cells (FC) and supercapacitors (SC) for an electrical microgrid located in the Renewable Energies Laboratory at the Public University of Navarre. Firstly, the hybrid storage system size was determined based on an energy and frequency analysis of real data for the electrical power generated and consumed in the microgrid over the course of a year in operation. This was followed by the experimental characterisation of the electrical behaviour of the FCs and SCs, in steady-state and dynamic modes of operation. Furthermore, an electrical model was developed for the FCs and another for the SCs, both of which gave satisfactory results in the experimental validations. Finally, a study was made of the storage system, comprising four 1.2 kW proton exchange membrane fuel cells (PEMFC) and three SCs of 83.3 F and 48.6 V each, in a real microgrid operating environment. Specifically, a comparison was made between the storage system solely comprising FCs and the hybrid storage system formed by a combination of FCs and SCs. The hybridisation of the FCs and SCs resulted in a complete, high-capacity energy storage system, to guarantee supply even in those months with low renewable energy resources and, in turn, able to provide the fast dynamic responses regularly required by supply and demand in the microgrid.     

Techno-economic and behavioural analysis of battery electric,hydrogen fuel cell and hybrid vehicles in a future sustainable road transport system in the UK

This paper conducts a techno-economic study on hydrogen Fuel Cell Electric Vehicles (FCV), Battery Electric Vehicles (BEV) and hydrogen Fuel Cell plug-in Hybrid Electric Vehicles (FCHEV) in the UK using cost predictions for 2030. The study includes an analysis of data on distance currently travelled by private car users daily in the UK. Results show that there may be diminishing economic returns for Plug-in Hybrid Electric Vehicles (PHEV) with battery sizes above 20 kWh, and the optimum size for a PHEV battery is between 5 and 15 kWh. Differences in behaviour as a function of vehicle size are demonstrated, which decreases the percentage of miles that can be economically driven using electricity for a larger vehicle. Decreasing carbon dioxide emissions from electricity generation by 80% favours larger optimum battery sizes as long as carbon is priced, and will reduce emissions considerably. However, the model does not take into account reductions in carbon dioxide emissions from hydrogen generation, assuming hydrogen will still be produced from steam reforming methane in 2030.     

Experimental platform for development and Evaluation of hybrid generation systems based on fuel cells

An experimental hybrid power generation platform for the design and assessment of advanced control systems has been developed. It is specifically intended as a flexible development tool for the implementation and refinement of real-time novel control algorithms, aimed to maximize energy efficiency and optimize the electrical power management of hybrid generation systems based on fuel cells. The platform consists of two generation modules and storage module. The main one is based on a PEM fuel cell stack. The second one, implemented with a programmable electronic source, allows to emulate an alternative energy module, particularly a wind energy generation system. The storage module is built with Supercapacitors. Finally, a variable electronic load represents the lumped energy demand, with profiles that can be programmed in accordance with the user requirements. All modules of the system are connected to a common DC bus through intermediary electronic converters, which are controlled by a dedicated digital signal processor. The complete system is supervised through a Personal Computer, resulting into a highly versatile platform. Experimental results are presented to validate the whole system performance.     

Comparative analysis of battery electric,hydrogen fuel cell and hybrid vehicles in a future sustainable road transport system

This paper compares battery electric vehicles (BEV) to hydrogen fuel cell electric vehicles (FCEV) and hydrogen fuel cell plug-in hybrid vehicles (FCHEV). Qualitative comparisons of technologies and infrastructural requirements, and quantitative comparisons of the lifecycle cost of the powertrain over 100,000 mile are undertaken, accounting for capital and fuel costs. A common vehicle platform is assumed. The 2030 scenario is discussed and compared to a conventional gasoline-fuelled internal combustion engine (ICE) powertrain. A comprehensive sensitivity analysis shows that in 2030 FCEVs could achieve lifecycle cost parity with conventional gasoline vehicles. However, both the BEV and FCHEV have significantly lower lifecycle costs. In the 2030 scenario, powertrain lifecycle costs of FCEVs range from $7360 to $22,580, whereas those for BEVs range from $6460 to $11,420 and FCHEVs, from $4310 to $12,540. All vehicle platforms exhibit significant cost sensitivity to powertrain capital cost. The BEV and FCHEV are relatively insensitive to electricity costs but the FCHEV and FCV are sensitive to hydrogen cost. The BEV and FCHEV are reasonably similar in lifecycle cost and one may offer an advantage over the other depending on driving patterns. A key conclusion is that the best path for future development of FCEVs is the FCHEV.     

MPPT controller for an interleaved boost dc–dc converter used in fuel cell electric vehicles

Fuel cell electric vehicle (FCEV) has recently attracted increasing research interest. This paper investigates the performances of MPPT-FC generators supplying electric vehicle power train through an interleaved boost DC/DC converter (IBC). The accent is made on forcing the FC generator to operate at its maximum power point by using perturb and observe (P&O) algorithm integrated to the IBC control. However, the MPPT-FC control creates rapid changes in the power output from the fuel cell, which cause serious life shortening, severe cell degradation, and decrease the system efficiency. To overcome these shortcomings, the control of air generation system was designed to improve the power quality and to prevent fuel starvation phenomenon during rapid power transitions. The work involves the modeling and the simulation of the fuel cell power train in the vehicular application using the experimental data obtained in previous works. The experimental part of the proposed FCEV is based on a low-cost, low-power consumption microcontroller, which controls the IBC and performs the MPPT-FC operation. A microcontroller is used to measure the FC output power and to change the duty ratio of the IBC control signals.     

Experimental study of energy management of FC/SC hybrid system using the Passivity Based Control

Nowadays, the energy management of the hybrid system is becoming an interesting and the challenging topic for several researchers. The wise choice of the energy management strategy allows not only the best distribution of power between different sources but also reduce system consumption, increase the lifetime of the used sources and ensure the energy demand that involve the autonomy of the electrical vehicle. In this paper, the control and the energy management using the passivity control is adopted to the multiconverters multisources system, in particularly, Fuel Cell/SuperCapacitor (FC/SC) hybrid system. In the proposed system, the FC represents the main source and the SC is used for the transient of power where they can absorb or supply powers peaks. The proposed system is validated by experimental results. The obtained results prove the efficacy and the feasibility of the proposed approach for a real electrical vehicle.     

Stabilised control strategy for PEM fuel cell and supercapacitor propulsion system for a city bus

Fuel Cell (FC) buses have been developed as a long term zero emission solution for city transportation and have reached levels of maturity to supplement the coming London 2020 Ultra low emission zone implementation. This research developed a scaled laboratory Fuel Cell/Supercapacitor hybrid drivetrain implementing DC/DC converters to maintain the common busbar voltage and control the balance of power. A novel and simple hybrid control strategy based on balancing the currents on the common busbar whilst maintaining a stable FC output has been developed. It has been demonstrated that the FC power output can be controlled at a user defined value for both steady state and transient load conditions. The proposed control strategy holds the promise of extending FC life, downsizing power systems and improving the FC operating efficiency.     

Designing, building, testing and racing a low-cost fuel cell range extender for a motorsport application

Imperial Racing Green is an undergraduate teaching project at Imperial College London. Undergraduate engineers have designed, built and raced hydrogen fuel cell hybrid vehicles in the Formula Zero and Formula Student race series. Imperial Racing Green has collaborated with its fuel cell partners to develop a 13 kW automotive polymer electrolyte membrane fuel cell (PEMFC) system. A team of undergraduate engineers were given a relatively modest budget and less than 8 months to design and assemble an operational high-power PEMFC system. The fuel cell system was designed to provide the average power required by the team's 2011 Formula Student entry. This paper presents the team's experience of developing and testing an automotive fuel cell system for a race application and plans for its future development and integration onto the vehicle.     

Comparison among various energy management strategies for reducing hydrogen consumption in a hybrid fuel cell/supercapacitor/battery system

The aim of this study is to introduce a comprehensive comparison of various energy management strategies of fuel cell/supercapacitor/battery storage systems. These strategies are utilized to manage the energy demand response of hybrid systems, in an optimal way, under highly fluctuating load condition. Two novel strategies based on salp swarm algorithm (SSA) and mine-blast optimization are proposed. The outcomes of these strategies are compared with commonly used strategies like fuzzy logic control, classical proportional integral control, the state machine, equivalent fuel consumption minimization, maximization, external energy maximization, and equivalent consumption minimization. Hydrogen fuel economy and overall efficiency are used for the comparison of these different strategies. Results demonstrate that the proposed SSA management strategy performed best compared with all other used strategies in terms of hydrogen fuel economy and overall efficiency. The minimum consumed hydrogen and maximum efficiency are found 19.4 gm and 85.61%, respectively.     

Minimum time current controller design for two-interleaved bidirectional converter: Application to hybrid fuel cell/supercapacitor vehicles

In fuel cell hybrid vehicles (FCHV) with a supercapacitor (SC) used as auxiliary source of hybridization, classical SC converters limit the current tracking performance due to the presence of a large input inductance. A hardware solution to this issue consists in using an interleaved converter topology that enables considerably reducing the input inductance. To optimize interleaved converters usage, an intelligent control scheme that maximizes closed-loop performance in current tracking must be designed. For that purpose, we design two controllers: a transient-state controller and a steady-state one. The first controller is a bang-bang one that guaranties a fast transition from the initial condition to some closed region around the reference. The second controller ensures the local asymptotic stabilization of a certain desired limit cycle and is based on switching surfaces design. The proposed control scheme performances and robustness are evaluated through simulations with piece-wise constant source and reference current. Performances are also evaluated on a battery-like supercapacitor vehicle using an urban driving cycle.     

The characteristics of regenerative energy for PEMFC hybrid system with additional generator

This study focuses on the use of the Polymer Electrolyte Membrane Fuel Cell (PEMFC) hybrid system, which consists of a generator, a supercapacitor, and a battery, to obtain regenerative energy. The fuel cell is a Nexa™ Power Module of Ballard Power Systems Inc., and the battery is a Ni-MH battery of Global Battery Co., Ltd. The supercapacitor, which features an excellent power density and capacity of 30 V and 100F, can minimize its power consumption via a cell balancing circuit. This study aimed to evaluate the characteristics of regenerative energy and suggest solutions to increase regenerative energy using a vehicle simulation.