Browsing by Author "Yuan, Hsiang-Fu"

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A Digital Boost Converter for Fuel Cell Current Regulation in Hybrid Power Systems
(2016)
Dung, Lan-Rong
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Yu, Hung-Ming
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Yuan, Hsiang-Fu
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電機工程學系
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電控工程研究所
Fuel cell (FC)/lithium-ion battery hybrid power system (HPS) gradually becomes a powerful energy source in the future. This paper presents a digital boost converter for FC current regulation in the HPS with a dual-battery energy storage unit (ESU). The digital boost converter regulates the FC current in order to control the FC power generation. Simulations have been conducted in PSIM environment, and the digital controller is implemented with a Microchip dsPIC33FJ06GS202 16-bit microcontroller. Experimental results show that the efficiency of power conversion can reach to 85%.
A Hybrid Fuel Cell-Battery Power System
(2014)
Yuan, Hsiang-Fu
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Dung, Lan-Rong
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資訊工程學系
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電機學院
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Department of Computer Science
This paper presents a new hybrid power system with battery depth-of-discharge (DOD) management for extending battery cycle life and system service time. The proposed power system consists of a power management system, a dual-battery unit, a fuel cell (FC) stack, and two dc/dc unidirectional power converters. The dual-battery unit serves as the primary power source, while the FC stack serves as the secondary power source. The proposed power management is based on a state-machine-based mechanism, using a battery interchanging strategy to limit batteries operating within a given DOD range. The state-machine-based mechanism is employed for reducing the effects of battery overcharging or overdischarging; thus, it can significantly improve the battery life time. In addition, this algorithm has the ability to distribute the power flow efficiently between the dual batteries and the FC stack, and also to keep providing a stable and continuous energy output for the load. A current-mode control dc/dc boost converter is designed to regulate the FC current and try to maximize the FC power for battery charging time reduction. The proposed hybrid system introduced in this paper is designed and implemented with a 20W proton exchange membrane fuel cell (PEMFC) stack and two 12Ah lithium iron phosphate (LiFePO4) batteries. The experimental results of capacity fades on various DOD tests verify the usefulness of the proposed fuel cell/dual batteries hybrid power system. The comparison of life improvement is also shown in test results.
A Hybrid Fuel Cell-Battery Power System
(2014-01-01)
Yuan, Hsiang-Fu
;
Dung, Lan-Rong
;
電機工程學系
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Department of Electrical and Computer Engineering
This paper presents a new hybrid power system with battery depth-of-discharge (DOD) management for extending battery cycle life and system service time. The proposed power system consists of a power management system, a dual battery unit, a fuel cell (EC) stack, and two de/de unidirectional power converters. The dual-battery unit serves as the primary power source, while the FC stack serves as the secondary power source. The proposed power management is based on a state machine -based mechanism, using a battery interchanging strategy to limit batteries operating within a given DOD range. The state machine -based mechanism is employed for reducing the effects of battery overcharging or overdischarging; thus, it can significantly improve the battery life time. In addition, this algorithm has the ability to distribute the power flow efficiently between the dual batteries and the FC stack, and also to keep providing a stable and continuous energy output for the load. A current mode control dc/dc boost converter is designed to regulate the EC current and try to maximize the FC power for battery charging time reduction. The proposed hybrid system introduced in this paper is designed and implemented with a 20W proton exchange membrane fuel cell (PEMEC) stack and two I2Ah lithium iron phosphate (LiFePO4) batteries. The experimental results of capacity fades on various DOD tests verify the usefulness of the proposed fuel cell/dual batteries hybrid power system. The comparison of life improvement is also shown in test results.
A Lithium-Ion Battery Simulator Based on a Diffusion and Switching Overpotential Hybrid Model for Dynamic Discharging Behavior and Runtime Predictions
(2016-01-01)
Dung, Lan-Rong
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Yuan, Hsiang-Fu
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Yen, Jieh-Hwang
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She, Chien-Hua
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Lee, Ming-Han
A new battery simulator based on a hybrid model is proposed in this paper for dynamic discharging behavior and runtime predictions in existing electronic simulation environments, e.g., PSIM, so it can help power circuit designers to develop and optimize their battery-powered electronic systems. The hybrid battery model combines a diffusion model and a switching overpotential model, which automatically switches overpotential resistance mode or overpotential voltage mode to accurately describe the voltage difference between battery electro-motive force (EMF) and terminal voltage. Therefore, this simulator can simply run in an electronic simulation software with less computational efforts and estimate battery performances by further considering nonlinear capacity effects. A linear extrapolation technique is adopted for extracting model parameters from constant current discharging tests, so the EMF hysteresis problem is avoided. For model validation, experiments and simulations in MATLAB and PSIM environments are conducted with six different profiles, including constant loads, an interrupted load, increasing and decreasing loads and a varying load. The results confirm the usefulness and accuracy of the proposed simulator. The behavior and runtime prediction errors can be as low as 3.1% and 1.2%, respectively.
A Robust, Intelligent CC-CV Fast Charger for Aging Lithium Batteries
(2016)
Dung, Lan-Rong
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Chen, Chieh-En
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Yuan, Hsiang-Fu
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電機工程學系
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電控工程研究所
This paper proposes a robust, intelligent constant current-constant voltage (CC-CV) charger for fast charging an aging Lithium-ion battery. Increasing the charging current in the CC regime cannot guarantee the short charging time, so an optimal charging current exists in the CC-CV method. The optimal charging current changes with battery degradation, so this paper figures out a way to find the optimal charging current by applying direct current internal resistance (DCIR) tests before the CC-CV charging method. The experiment results show that the proposed charger can adjust the optimal current based on battery state-of-health (SOH). The charging time has a 6.5% improvement when it is compared to a standard CC-CV fast charger.
An Aging-Compatible Inductor-Based Equalization Mechanism for LFP Batteries
(2015)
Dung, Lan-Rong
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Song, Zhe-Yuan
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Yuan, Hsiang-Fu
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電機學院
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College of Electrical and Computer Engineering
This paper proposes an aging-compatible inductor-based equalization mechanism for LFP batteries. Due to the characteristic of flat voltage curve, voltage equalization does not always successfully balance a series-connected battery pack. The proposed inductor-based equalization mechanism is developed to smartly balance battery voltage in the right state-of-charge (SOC) region regardless of the extent of battery aging deterioration. The mechanism includes two parts: one is balancing trigger voltage search, and the other one is the balancing current control. Experimental results show that the proposed equalization mechanism can increase the 8.4% storage capacity of the fresh cell and the 3.6% storage capacity of the aging cell. The conventional equalization can increase the 8.3% storage capacity of the fresh cell but decrease the 2.7% storage capacity of the aging cell. The experimental results also prove that equalization at different stages are not always beneficial. Using the aging-compatible inductor-based equalization mechanism can obtain a better balancing performance.
An Anti-Racing PWM-based Battery Pack Equalization
(2014)
Dung, Lan-Rong
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Lin, Chieh-Tsen
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Yuan, Hsiang-Fu
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電機工程學系
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Department of Electrical and Computer Engineering
Following the trend of eco-conscious, the automakers tend to use high-voltage packs in the electric vehicle or hybrid electric vehicle. The packs are formed by battery cells in series and parallel connections. Because of the variation of battery production, their capacity, impedance, lifetime and chemistry characteristic vary with ambient temperature. When the batteries are charged or discharged as a pack, the differences result in the imbalance of the battery voltage. The imbalance turns out over-charged and over-discharged and shortens the capacity and lifetime of batteries. Among the equalization methods, resistively switching approach is widely used for its low complexity and low cost. The controller gauges the battery voltage no matter the equalization is on or off. The comparison of two battery voltages must be based on the charging current. If not, the racing phenomenon happens and the equalization circuit would be turned on and off frequently. PWM-based equalization can solve this problem. Detecting the voltages of the batteries when the duty is off ensures the battery voltages are both based on the charging current. The PWM-based equalization successfully eliminates the racing phenomenon and shortens charging time by 48%; from 6200 seconds of switching shunt resistor equalization to 3200 seconds.
An SOH Estimation System Based on Time-Constant-Ratio Measurement
(2014-01-01)
Dung, Lan-Rong
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Wu, Sung-Han
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Yuan, Hsiang-Fu
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電機資訊學士班
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Undergraduate Honors Program of Electrical Engineering and Computer Science
The SOH of batteries is critical information for electric vehicle (EV) and hybrid electric vehicle (HEV) systems. This paper proposes an SOH estimation system based on time-constant-ratio measurement. There are two reasons of choosing time-constant as aging criterion. First, time-constant represents the response speed of terminal voltage during charging and discharging. Second, time-constant represents the change of internal chemical reactions. The proposed estimation resolves the issues of traditional SOH estimations. There are two widely used SOH estimations. The first one is full-charge-capacity (FCC) estimation. Unfortunately, to access FCC information need to take a long-term charging and discharging test. Therefore, FCC estimation fails to be a fast SOH estimation. The second estimation is internal impedance estimation. However, this SOH estimation may cause large error due to the effect of environmental impedance. For improving the above issues on different SOH estimations, this paper proposes an SOH estimation system based on time-constant-ratio measurement. The time-constant-ratio is a novel criterion for aging effect. The use of this novel criterion for SOH estimation helps to achieve the purpose of an environmental-impedance-free and fast SOH estimation. The proposed estimation is 0.14% the measured time of FCC estimation based on 1C charging and discharging. The measured results have average error below 1% and maximum error below 2%.
Effect of External Resistance on SOH Measurement of LFP Cells
(2015)
Yuan, Hsiang-Fu
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Dung, Lan-Rong
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電控工程研究所
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Institute of Electrical and Control Engineering
Due to the small ohmic resistance, such as the LFP battery, off-line state-of-health (SOH) estimation based on ohmic techniques faces a great challenge on measurement difficulty. The inaccurate measurement result of the ohmic resistance can cause a severe SOH error. This paper studies the influences of battery external resistance on the off-line SOH estimations using different model parameters in a first-order equivalent battery model. The sensitivity function is introduced here to assess performances of these model parameters. The several test results show that the transient resistance has the good ability against the external resistance effect. The sensitivity results of the transient resistance are all less 0.05 in different test cases. In addition, the SOHs estimated by the transient resistance and full charge capacity (FCC) in 600 cycling tests have the smallest average error (6.9%).
Offline State-of-Health Estimation for High-Power Lithium-Ion Batteries Using Three-Point Impedance Extraction Method
(2017-03-01)
Yuan, Hsiang-Fu
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Dung, Lan-Rong
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電機工程學系
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電控工程研究所
;
Department of Electrical and Computer Engineering
This paper presents an offline state-of-health (SoH) estimation based on charge transfer resistance for high-power lithium-ion (Li-ion) batteries, such as lithium iron phosphate (LFP) batteries. As shown in the experimental results, the charge transfer resistance has a great aging change with battery degradation and good abilities against state-of-charge (SoC) drift and external resistance variation in the impedance parameter set of a single-time-constant equivalent circuit model (ECM), including ohmic resistance, charge transfer resistance, double-layer capacitance, and time constant, for SoH estimation. A fast and efficient three-point (TP) impedance extraction method is also proposed in this paper for accurately extracting the charge transfer resistance in offline SoH estimation. The results of long-term cycling test demonstrate that the TP impedance extraction method can successfully indicate the SoH of LFP batteries with low estimation error of 6.1%.