• KEPCO Journal on Electric Power and Energy
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• v.5 no.2
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• pp.113-120
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• 2019

We have developed 1 kW-class PEMFC-battery hybrid system independently powering to the building, through the process of system design, current load characteristics analysis, power system configuration for demonstration site and performance evaluation. In order to use the fuel cell and battery as the hybrid type, a control technology for the charging/discharging decision and charging speed of the battery is required rather than using fuel cell. Also output power distribution between PEMFC and the battery is a core of energy management technology. It is confirmed that it is possible to supply independently 1kW powering the building to ensure optimal energy management through the power control experiment of the hybrid system.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.2
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• pp.155-162
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• 2019

The energy management technology for an independent fuel cell-battery hybrid system is developed for a household usage. To develop an efficient energy management technology, a simulation model is first developed. After the model is verified with experimental results, three energy management schemes are developed. Three control techniques are a fuzzy logic control (FLC), a state machine control (SMC), and a hybrid method of FLC and SMC. As the fuel cell-battery hybrid system is used for a house, battery state of charge (SOC) regulation is the most important factor for an energy management because SOC should be kept constant every day for continuous usage. Three management schemes are compared to see SOC, power split, and fuel cell power variations effects. Experimental results are also presented and the most favorable strategy is the state machine combined fuzzy control method.

• Transactions of the Korean hydrogen and new energy society
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• v.15 no.1
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• pp.1-11
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• 2004

Hybrid power systems with fuel cells and batteries have the potential to improve the operation efficiency and dynamic response. A proper load management strategy is important to better system efficiency and endurance in hybrid systems. In this paper, a fuzzy logic algorithm has been used to determine the fuel cell output power depending on the external required power and the battery state of charge(SoC). If the required power of the hybrid system is small and the SoC is small, then the greater part of the fuel cell power is used to charge the battery pack. If the required power is relatively big and the SoC is big, then fuel cell and battery are concurrently used to supply the required power. These IF-THEN operation rules are implemented by fuzzy logic for the energy management system of hybrid system. The strategy is evaluated by simulation. The results show that fuzzy logic can be effectively used to optimize the operational efficiency of hybrid system and to maintain the battery SoC properly.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.143.2-143.2
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• 2010

Therefore, with this development assignment we'd like to develop the hybrid system combining 800W DMFC (Direct Methanol Fuel Cell) and 1.6kW of Lithium secondary battery pack which can be applied to the most common small cart. a scooter, to secure the development capability of hundreds of Watts DMFC, the high-capacity Lithium secondary battery pack, the technology of BMS (Battery Management System) and the development technology of hybrid system. DMFC, in fact, has lower energy efficiency than PEMFC (Polymer Electrolyte Membrane Fuel Cell); however, it has several advantages in terms of fuel storage and use. It is pretty easy to be stored and used without any additional colling and heating devices because of its insensitive liquid methanol to temperature. In conclusion, DMFC system is the most suitable device for small mobile vehicles.

• New & Renewable Energy
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• v.9 no.4
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• pp.3-12
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• 2013

This paper proposes the hybrid fuel cell system that can solve disadvantages of existing fuel cell system and ensure high reliability and high stability. The system consists of PEM fuel cell, Ni-MH battery and power management system. In this system, when the power provided from the fuel cell is higher than the load power, the extra energy may be used to charge the Ni-MH battery. When the fuel cell can not provide enough energy to the load, the shortage of energy will be supplied by the Ni-MH battery. Experimental results show that the output voltage is regulated well during load variations. Also, high system efficiency is achieved.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1763-1769
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• 2007

To improve the cycle-life and efficiency of an energy storage system for HEV, a dynamic control system consisted of a switch between a battery and an ultracapacitor module is proposed, which is appropriate for mild hybrid vehicle with 42V power net. The switch can be controlled based on the status of the battery and the ultracapacitor module, and a control algorithm that could largely decrease the number of high charging current peak is also implemented. Therefore the cycle life of the battery can be improved such that it is suitable for a mild hybrid vehicle with frequent engine start-stop and regenerative-braking. Also, by maximizing the use of the ultracapacitor, the system efficiency during high current charging and discharging operation is improved. Finally, this system has the effects that improves the efficiency of energy storage system and reduces the fuel consumption of a vehicle. To verify the validity of the proposed system, this paper presented cycles test results of different energy storage systems: a simple VRLA battery, hybrid energy Pack (HEP, a VRLA battery in Parallel with Ultracapacitor) and a HEP with a switch that controlled by energy management system (EMS). From the experimental result, it was proved the effectiveness of the algorithm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3391-3398
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• 2015

Recently, the large scaled lead-acid battery is widely introduced to efficient operation of the photovoltaic system in many islands. but the demand of lithium-ion battery is getting increased by the operation of wind power and replacement of the lead-acid battery. And also, under the renewable portfolio standard(RPS) and energy efficiency resource standard(EERS) policy of Korea government, the introduction of energy storage system(ESS) has been actively increased. Therefore, this paper presents the operation algorithm of hybrid battery management system(BMS) using the lead-acid and lithium-ion batteries, in order to maximize advantage of each battery. In other words, this paper proposed the algorithm of state of charge(SOC) and hybrid operation algorithm to calculate the optimal composition rate considering the fixed cost and operation cost of each battery. From the simulation results, it is confirmed that the proposed algorithms are an effective tool to evaluate SOC and to optimally operate hybrid ESS.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.5
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• pp.357-363
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• 2021

Eco-friendly hybrid railroad propulsion system with fuel-cell and battery was suggested to reduce carbon dioxide gas and replace retired diesel railroads. Lithium-ion battery with high energy/power density and long lifetime is selected as the energy source at the battery side due to its excellent performance. However, the performance of lithium-ion batteries was affected by temperature, current rate, and operating condition. Temperature is known to be the most influential factor in changing battery parameters. In addition, appropriate thermal management is required to ensure the safe and effective operation of lithium-ion battery. Electro-thermal coupled model with varying parameter depends on temperature, and state-of-charge (SOC) is suggested to estimate battery temperature. The electric-thermal coupled model contains diffusion current using parameter identification by adaptive control algorithm when considering thermal diffusion effect. An experiment under forced convection was conducted using cylindrical cell and 18 parallel-connected battery module to demonstrate the method.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.631-640
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• 2016

A dual-mode power management for a hybrid-electric UAV with a cruise power of 200W is proposed and empirically verified. The subject vehicle is a low-speed long-endurance UAV powered by a solar cell, a fuel cell, and a battery pack, which operate in the same voltage bounds. These power sources of different operational characteristics can be managed in two different methods: passive management and active management. This study proposes a new power management system named PMS2, which employs a bypass circuit to control the individual power sources. The PMS2 normally operates in active mode, and the bypass circuit converts the system into passive mode when necessary. The output characteristics of the hybrid system with the PMS2 are investigated under simulated failures in the power sources and the conversion of the power management methods. The investigation also provides quantitative comparisons of efficiencies of the system under the two distinct power management modes. In the case of the solar cell, the efficiency difference between the active and the passive management is shown to be 0.34% when the SOC of the battery is between 25-65%. However, if the SOC is out of this given range, i.e. when the SOC is at 90%, using active management displays an improved efficiency of 6.9%. In the case of the fuel cell, the efficiency of 55% is shown for both active and passive managements, indicating negligible differences.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.11
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• pp.930-937
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• 2012

Newly developed Series hybrid low-floor articulated vehicle which can meet both road and railway running conditions. It has the rated driving speed of 80 km/h and three driving modes with hybrid(engine+battery) driving mode, engine driving mode, battery driving mode. The battery driving mode requires the several 10 km running without additional charging operation. The vehicle has been equipped with LPB (lithium polymer battery) pack for the series hybrid propulsion system. LPB pack consists of 168 cells (3.7 V in a cell, 80 Ah) in series, DC Circuit breaker, mechanical rack, BMS (battery management system). This paper has shown the design process of LPB pack and application to the vehicle. Driving results in the road was successful to be satisfied with the requirement of the series hybrid vehicle.