Model-based fault detection of hybrid fuel cell and photovoltaic direct current power sources

Hybrid DC power sources which consist of fuel cells, photovoltaic and lithium-ion batteries provide clean, high efficiency power supply. This hybrid DC power sources can be used in many applications. In this work, a model-based fault detection methodology for this hybrid DC power sources is presented. Firstly, the dynamic models of fuel cells, photovoltaic and lithium-ion batteries are built. The state space model of hybrid DC power sources is obtained by linearizing these dynamic models in operation points. Based on this state space model the fault detection methodology is proposed. Simulation results show that model-based fault detection methodology can find the fault on line, improve the generation time and avoid permanent damage to the equipment.     

Agent-based power sharing scheme for active hybrid power sources

The active hybridization technique provides an effective approach to combining the best properties of a heterogeneous set of power sources to achieve higher energy density, power density and fuel efficiency. Active hybrid power sources can be used to power hybrid electric vehicles with selected combinations of internal combustion engines, fuel cells, batteries, and/or supercapacitors. They can be deployed in all-electric ships to build a distributed electric power system. They can also be used in a bulk power system to construct an autonomous distributed energy system. An important aspect in designing an active hybrid power source is to find a suitable control strategy that can manage the active power sharing and take advantage of the inherent scalability and robustness benefits of the hybrid system. This paper presents an agent-based power sharing scheme for active hybrid power sources. To demonstrate the effectiveness of the proposed agent-based power sharing scheme, simulation studies are performed for a hybrid power source that can be used in a solar car as the main propulsion power module. Simulation results clearly indicate that the agent-based control framework is effective to coordinate the various energy sources and manage the power/voltage profiles.     

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.     

A new topology of fuel cell hybrid power source for efficient operation and high reliability

This paper analyzes a new fuel cell Hybrid Power Source (HPS) topology having the feature to mitigate the current ripple of the fuel cell inverter system. In the operation of the inverter system that is grid connected or supplies AC motors in vehicle application, the current ripple normally appears at the DC port of the fuel cell HPS. Consequently, if mitigation measures are not applied, this ripple is back propagated to the fuel cell stack. Other features of the proposed fuel cell HPS are the Maximum Power Point (MPP) tracking, high reliability in operation under sharp power pulses and improved energy efficiency in high power applications. This topology uses an inverter system directly powered from the appropriate fuel cell stack and a controlled buck current source as low power source used for ripple mitigation. The low frequency ripple mitigation is based on active control. The anti-ripple current is injected in HPS output node and this has the LF power spectrum almost the same with the inverter ripple. Consequently, the fuel cell current ripple is mitigated by the designed active control. The ripple mitigation performances are evaluated by indicators that are defined to measure the mitigation ratio of the low frequency harmonics. In this paper it is shown that good performances are obtained by using the hysteretic current control, but better if a dedicated nonlinear controller is used. Two ways to design the nonlinear control law are proposed. First is based on simulation trials that help to draw the characteristic of ripple mitigation ratio vs. fuel cell current ripple. The second is based on Fuzzy Logic Controller (FLC). The ripple factor is up to 1% in both cases.     

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.     

Optimal sizing of a fuel processor for auxiliary power applications of a fuel cell-powered passenger car

The present study considers the optimal sizing of a three-way hybrid powertrain consisting of a compact reformer, a compact battery and a low temperature PEM fuel cell stack serving as the main power unit. A simulation model consisting of the relevant characteristic parameters of the three power sources has been developed and has been used to study the fuel utilization features of the hybrid powertrain while going through the NEDC driving cycle with a given auxiliary power requirement. The optimality is based on minimizing fuel cost while having an assured range of 500 km under practical driving conditions and a further 100 km under reduced auxiliary power usage. It is shown that for performance characteristics of Toyota Mirai and for average auxiliary power consumption of 5 kW, a smaller NiMH battery size of 1.3 kWh together with a fuel processor of 5.6 kW constant output would be optimal with a further requirement of 25% more hydrogen and 33 kg of ethanol to be carried on-board. Substantial reductions in vehicle mass and fuel load can be achieved for more modest performance characteristics and auxiliary power consumption.     

Fuel-cell sharing for a distributed hybrid power system

This paper investigates the benefits of sharing a proton exchange membrane fuel cell (PEMFC) in a distributed hybrid power system. The PEMFC is usually used as backup power in stationary hybrid power systems; however, in that scenario, it might be working only 2% of the time while incurring 20% of the system expenses. Therefore, this paper examines the potential of sharing a PEMFC among multiple power systems. We develop a distributed hybrid power system that comprises several immovable power stations and a fuel-cell vehicle (FCV). Each power station is equipped with solar panels and batteries, while the FCV contains a PEMFC module and can move among the stations to provide sustainable power as needed. We propose power management strategies and show that the total system costs can be significantly reduced by 10.83% and 17.89% when sharing one FCV between three and twelve power stations, respectively. We also design experiments to demonstrate the feasibility of the proposed distributed hybrid power system. In the future, the developed model can be extended to provide further cost reductions by optimizing distributed hybrid power systems with multiple FCVs.     

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.     

Sulfonated polyimide hybrid membranes for polymer electrolyte fuel cell applications

Sulfonated Si-MCM-41 (SMCM) with an ion exchange capacity (IEC) of 2.3 mequiv. g⁻¹ was used as a hydrophilic and proton-conductive inorganic component. Sulfonated polyimide (SPI) based on 1,4,5,8-naphthalene tetracarboxylic dianhydride and 2,2′-bis(3-sulfophenoxy) benzidine was used as a host membrane component. The SMCM/SPI hybrid membrane (H1) with 20 wt% loading of SMCM and an IEC of 1.90 mequiv. g⁻¹ showed the high mechanical tensile strength and the slightly higher water vapor sorption than the host SPI membrane (M1) with an IEC of 1.86 mequiv. g⁻¹. H1 and M1 showed anisotropic membrane swelling with about 10 times larger swelling in thickness direction than in plane one. The proton conductivity at 60 °C of H1 was lower in water than that of M1, but comparable at 30% RH. At 90 °C, H1 showed the rather lower performance of polymer electrolyte fuel cell (PEFC) at 82% RH than M1 and fairly better performance at 30% RH. On the other hand, at 110 °C and low humidity less than 50% RH, H1 showed the much better PEFC performance than M1 and Nafion 112. This was due to the promoted back diffusion of produced water by the superior water-holding capacity of SMCM. The SMCM/SPI hybrid membranes have high potential for PEFCs at higher temperatures and lower humidities.     

Intelligent uninterruptible power supply system with back-up fuel cell/battery hybrid power source

This paper presents the development of an intelligent uninterruptible power supply (UPS) system with a hybrid power source that comprises a proton-exchange membrane fuel cell (PEMFC) and a battery. Attention is focused on the architecture of the UPS hybrid system and the data acquisition and control of the PEMFC. Specifically, the hybrid UPS system consists of a low-cost 60-cell 300 W PEMFC stack, a 3-cell lead–acid battery, an active power factor correction ac–dc rectifier, a half-bridge dc–ac inverter, a dc–dc converter, an ac–dc charger and their control units based on a digital signal processor TMS320F240, other integrated circuit chips, and a simple network management protocol adapter. Experimental tests and theoretical studies are conducted. First, the major parameters of the PEMFC are experimentally obtained and evaluated. Then an intelligent control strategy for the PEMFC stack is proposed and implemented. Finally, the performance of the hybrid UPS system is measured and analyzed.     

New materials for polymer electrolyte membrane fuel cell current collectors

Polymer Electrolyte Membrane Fuel cells for automotive applications need to have high power density, and be inexpensive and robust to compete effectively with the internal combustion engine. Development of membranes and new electrodes and catalysts have increased power significantly, but further improvements may be achieved by the use of new materials and construction techniques in the manufacture of the bipolar plates. To show this, a variety of materials have been fabricated into flow field plates, both metallic and graphitic, and single fuel cell tests were conducted to determine the performance of each material. Maximum power was obtained with materials which had lowest contact resistance and good electrical conductivity. The performance of the best material was characterised as a function of cell compression and flow field geometry.     

Experimental evaluation of a passive fuel cell/battery hybrid power system for an unmanned ground vehicle

Unmanned vehicles are increasing the performance of monitoring and surveillance in several applications. Endurance is a key issue in these systems, in particular in electric vehicles, powered at present mainly by batteries. Hybrid power systems based on batteries and fuel cells have the potential to achieve high energy density and specific energy, increasing also the life time and safe operating conditions of the power system. The objective of this research is to analyze the performance of a passive hybrid power system, designed and developed to be integrated into an existing Unmanned Ground Vehicle (UGV). The proposed solution is based on six LiPo cells, connected in series, and a 200 W PEM fuel cell stack, directly connected in parallel to the battery without any limitation to its charge. The paper presents the characterization of the system behavior, and shows the main results in terms of performance and energy management.     

A review of fuel cell based hybrid power supply architectures and algorithms for household appliances

Nowadays, renewable power system solutions are widely investigated for residential applications. Grid-connected systems including energy storage elements are designed. Advanced research is actually focused on improving the reliability and energy density of renewable systems reducing the whole utility cost. Source and load modeling, power architectures and algorithms are only a few topics to be addressed. Designers have to carefully deal with each subtopic prior to design efficient renewable energy systems. In the literature, each topic is separately discussed and the lack of a unique reference guide is clear to power electronics designers. In this paper, each design step including source and load modeling, hybrid supply architectures and power algorithms, is carefully addressed. A review of existing solutions is presented. The correlation between each topic is deeply analyzed. Guidelines for system design are given. This paper can be referenced as a detailed review of renewable energy system design issues and solutions.     

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.     

Design of a hybrid electric fuel cell power train for an urban bus

With the requirements for reducing emissions and improving fuel economy, new markets have become attractive for automotive companies that are developing electric, hybrid, and plug-in vehicles using new technologies candidates to be implemented in the next generations of vehicles. Most of all, hybrid vehicles are attracting interest due to great potential to achieve higher fuel economy and a longer range with respect to pure electric mode but often this solution is not petroleum free. Within a national project CNR TAE Institute is involved in the development of a zero emission hybrid electric city bus based on PEM fuel cell technology able to increase the range at least 30% with respect to the same vehicle in pure electric configuration. Design, control and preliminary results are reported in this paper.     

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.     

Overview of hybrid membranes for direct-methanol fuel-cell applications

The direct-methanol fuel cell (DMFC), a type of polymer-electrolyte membrane fuel cell, has lately received much attention because of its potential applicability as a good alternative power source for the future. In order to achieve commercially viable performance goals for the DMFC, a membrane with several important selective behaviors will need to be developed. Over roughly the past four decades, researchers have used the commercial Nafion membrane by DuPont as a proton-conductive membrane in DMFCs due to its chemical stability and high proton conductivity, as well as high mechanical strength. However, Nafion membranes also have several weaknesses such as high methanol permeability and an operational temperature limited to ∼100 °C or lower, and Nafion is also a very expensive material. Besides Nafion, there have been several engineering thermoplastic polymers such as poly(etheretherketone) (PEEK), polysulfone (PSF) and polybenzimidazole (PBI) used as alternative membranes due to their lower cost and very high mechanical and thermal stability in high temperature operation. To date, there has been continuous extensive research on developing a membrane which can fulfill all of the essential characteristics to yield the desired performance in DMFCs. In the course of this research, hybrid membranes have been developed by modifying the original membranes to produce new membranes with variously enhanced properties. This review discusses recent advances in hybrid membranes of two main types: Nafion-based and non-Nafion-based membranes. Recent achievements and prospect of applications also been included in this paper.     

Comparative studies of polymer electrolyte membrane fuel cell stack and single cell

The polymer electrolyte membrane fuel cell (PEMFC) was investigated comparatively as a single cell and a 30-cell stack. Various types of Nafion membranes, such as Nafion 117, 115, 112 and 105, were tested as electrolyte within the single cell and at different temperatures, among which Nafion 112 gave the optimal result. The 30-cell stack was evaluated at different humidities and temperatures. The potential–current and power–current curves, both for single cell and the stack, were analyzed by computer simulation, whereby the kinetic and mass-transfer parameters were calculated. The long-term performance of the stack and the water production during long-term operation were also measured.     

Optimization of distributed hybrid power systems employing multiple fuel-cell vehicles

This paper investigates the benefits of distributed hybrid power systems employing multiple fuel-cell vehicles. In earlier work, our optimization of hybrid power systems showed that a single fuel cell acting as backup power to guarantee energy sustainability operates for less than 3% of the time but incurs more than 16% of the system costs. Therefore, the system cost could be reduced when applying a fuel-cell vehicle to dynamically support twelve power stations. Here, we extend this idea by employing multiple fuel-cell vehicles to support more power stations. We develop a power management strategy and optimize the management parameters by the genetic algorithm. The results show a reduction of more than 21% by applying multiple fuel-cell vehicles in the distributed systems. Experiments also confirm the feasibility of using multiple fuel-cell vehicles. Based on the results, the proposed systems are deemed effective for reducing system costs while maintaining system sustainability.     

A mobile renewable house using PV/wind/fuel cell hybrid power system

A photovoltaic/wind/fuel cell hybrid power system for stand-alone applications is proposed and demonstrated with a mobile house. This concept shows that different renewable sources can be used simultaneously to power off-grid applications. The presented mobile house can produce sufficient power to cover the peak load. Photovoltaic and wind energy are used as primary sources and a fuel cell as backup power for the system. The power budgeting of the system is designed based on the local data of solar radiation and wind availability. Further research will focus on the development of the data acquisition system and the implementation of automatic controls for power management.