Panarit Sethakul

Comparative Study of Fuel-Cell Vehicle Hybridization with Battery or Supercapacitor Storage Device

This paper studies the impact of fuel-cell (FC) performance and control strategies on the benefits of hybridization. One of the main weak points of the FC is slow dynamics dominated by a temperature and fuel-delivery system (pumps, valves, and, in some cases, a hydrogen reformer). As a result, fast load demand will cause a high voltage drop in a short time, which is recognized as a fuel-starvation phenomenon. Therefore, to employ an FC in vehicle applications, the electrical system must have at least an auxiliary power source to improve system performance when electrical loads demand high energy in a short time. The possibilities of using a supercapacitor or a battery bank as an auxiliary source with an FC main source are presented in detail. The studies of two hybrid power systems for vehicle applications, i.e., FC/battery and FC/supercapacitor hybrid power sources, are explained. Experimental results with small-scale devices (a polymer electrolyte membrane FC of 500 W, 40 A, and 13 V; a lead-acid battery module of 33 Ah and 48 V; and a supercapacitor module of 292 F, 500 A, and 30 V) in a laboratory authenticate that energy-storage devices can assist the FC to meet the vehicle power demand and help achieve better performance, as well as to substantiate the excellent control schemes during motor-drive cycles.

Fuel Cell Current Ripple Mitigation by Interleaved Technique for High Power Applications

This paper presents a fuel cell (FC) current ripple mitigation by interleaved algorithm for high power dc distributed system supplied by a FC generator. The major problems of operating a FC in high power applications is high FC ripple current, in which may lead to reduce its stack lifetime. Thus, to improve the FC stack lifetime, a proposed parallel power converter with interleaving technique is chosen to boost a low dc voltage of FC to a dc bus utility level. The present interleaved step-up converters are composed of two and four identical boost converters connected in parallel. Converters are controlled by interleaved switching signals, which have the same switching frequency and the same phase shift. During the past decade, power electronics research has focused on the development of interleaved parallel converters. For an interleaving technique with a real FC source, this work is the first presentation; it is not just a FC simulation. So, the design and experimental verification of 1.2-kW prototype converters at a switching frequency of 25 kHz connected with a Nexa TM PEM fuel cell system (1.2-kW, 46-A) in a laboratory is presented. Experimental results corroborate the excellent system performances.

Analysis of a Fuel Starvation Phenomenon of a PEM Fuel Cell

This paper presents the characteristics of a PEM fuel cell, especially a fuel (hydrogen and oxygen) starvation problem. This phenomenon is an original demonstration in the domain of fuel cell research. Naturally, a fuel cell power source is always connected with a power electronic converter (power conditioning circuit) to boost a low dc voltage to a higher utility level. Therefore, to present fuel cell characteristics, a fuel cell power conditioning circuit (classical boost converter) is designed and implemented in the GREEN/INPL laboratory. The studied PEM fuel cell is 500 W, 40 A, around 13 V, designed and manufactured by the ZSW Company. Experimental results authenticate the fuel cell characteristics when the fuel cell power source is operated with a power electronic converter at a switching frequency of 25 kHz. The high switching frequency and significant step load (fuel starvation effect) to the fuel cell voltage and current are clearly illustrated.

Modeling and control of a fuel cell current control loop of a 4-phase interleaved step-up converter for DC distributed system

In a high power converter design for fuel cell applications, the usefulness of interleaving power converter module has become apparent. The benefits of interleaving include: reduced rms current in the do bus capacitors; ripple current cancellation in the input and output waveforms; reduction of size and volume of input inductors, enabling the simplicity to obtain Ferrite-core and Litz wire size; improved transient response as a result of reduced input inductance and higher input and output ripple frequency; separation of heat generating components; and power converter segmentations, enabling the superior reliability. So, this paper presents a fuel cell current control loop of the proposed 4-phase interleaved boost converter for high power fuel cell applications. Experimental results of the proposed FC converter (1.2-kW) at 25-kHz PWM switching frequency connecting with a Nexatrade PEM fuel cell (1.2-kW, 46-A,) collaborate the excellent performances: static and transient states of the design system.

Performance Evaluation of Fuel Cell/Battery/Supercapacitor Hybrid Power Source for Vehicle Applications

This paper proposes a high-power high-energy dc distributed generation system supplied by a polymer electrolyte membrane fuel cell (PEMFC) as a main power source and storage devices: battery and supercapacitor, for future fuel cell vehicle applications. The energy in hybrid system is balanced by the dc bus voltage regulation. The principle is based on frequency approach that the FC dynamics are limited to avoid fuel starvation problems and the battery dynamics are also limited to reduce its stress. As a result, the hybrid power source will increase its lifetime. 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.

Control of fuel cell/battery/supercapacitor hybrid source for vehicle applications

This paper presents a control algorithm for utilizing a polymer electrolyte membrane fuel cell (PEMFC) as a main power source and storage devices (batteries and supercapacitors) for dc distributed system, particularly for future FC vehicle applications. This strategy is based on a standard dc bus voltage regulation, which takes into account the slowest dynamics of a fuel cell (FC) and the fastest dynamics of a supercapacitor bank. The principle is based on frequency approach that the FC dynamics are limited to avoid fuel starvation problems and the battery dynamics are also limited to reduce its stress. Its originality lies in using only the supercapacitor for supplying the energy required to achieve the dc bus voltage regulation, the battery for supplying the energy to keep the supercapacitor charged, and the FC for supplying the energy to keep the battery charged. To validate the proposed principle, a hardware system is realized by analog circuits and numerical calculations 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) authenticate the excellent control algorithm during motor drive cycle.

Fuzzy logic based DC bus voltage control of a stand alone photovoltaic/fuel cell/supercapacitor power plant

A renewable energy hybrid power plant, fed by photovoltaic (PV) and fuel cell (FC) sources with a supercapacitor (SC) storage device and suitable for distributed generation applications, is proposed herein. The PV is used as the primary source; the FC acts as a backup and a long-term storage system, feeding only the insufficiency power (steady-state) from the PV; and the SC functions as an auxiliary source and a short-term storage system for supplying the deficiency power (transient and steady-state) from the PV and the FC. A mathematical model (reduced-order model) of the FC, PV, and SC converters is described for the control of the power plant. Using the intelligent fuzzy logic controller based on the flatness property for dc grid voltage regulation, we propose a simple solution to the dynamic optimization and stabilization problems in the power system. This is the key innovative contribution of this research paper. The prototype small-scale power plant implemented was composed of a PEMFC system (1.2 kW, 46 A), a PV array (0.8 kW), and a SC module (100 F, 32 V). Experimental results validate the excellent control algorithm during load cycles.

Modified 4-phase interleaved fuel cell converter for high-power high-voltage applications

This paper proposes a modified 4-phase paralleled step-up converter for fuel cell generator. In high power applications, the interleaving technique for paralleling input of the converter system has been studied for many years. Since component parasitic elements limit the practically realizable voltage-gain of any converter topology, this becomes a critical issue in the case of the classical step-up converter. The modified 4-phase interleaved fuel cell converter is studied for higher voltage conversion ratio. Since the fuel cell current is proportional to the fuel (hydrogen and oxygen) input, it is obligatory to have a fuel cell current control loop, in order to limit a high current transition of fuel cell to prevent the fuel starvation phenomenon. The average-current-control in continuous conduction mode for the proposed converter is analyzed in details. Classical PI controllers are selected for each current control loop. The fuel cell converter of 40-kW is studied for high power high voltage applications. Experimental and simulated results of the power converters authenticate the excellent performance of the studied fuel cell converter.

Control strategy of solar/wind energy power plant with supercapacitor energy storage for smart DC microgrid

This paper presents an original control algorithm for a hybrid energy system with a renewable energy source: a photovoltaic (PV) array and a wind turbine (WD). A single storage device, a supercapacitor (SC) module, is in the proposed structure. The very fast power response and high specific power of a SC complements the insufficient power output of the main sources to produce the compatibility and performance characteristics needed in a load. To verify the proposed principle, a hardware system is realized with analog circuits and with numerical calculation (dSPACE) for the energy control loops. Experimental results with small-scale devices, namely, a wind turbine generator (500 W), a photovoltaic array (800 W, 31 A) manufactured by the Ekarat Solar Company and a SC module (100 F, 32 V), illustrate the excellent energy-management scheme during load cycles.

A dynamic equivalent circuit model for gas diffusion layers of PEMFC

Proton exchange membrane fuel cell (PEMFC) is a device that converts hydrogen and oxygen to electricity. Power electronic converter is an important equipment to transfer energy from PEMFCs to loads properly. The PEMFC model suited for integrating with power electronic circuit simulation are the empirical and the equivalent circuit types. The gas diffusion layer is important part of the PEMFC. This part determines the limit condition of the PEMFC. However, the equivalent circuit model of the gas diffusion layer is not available. This paper proposes a dynamic equivalent circuit model for the GDL and its simulation.