Jung-Hoon Ahn

Enhanced Coulomb counting method with adaptive SOC reset time for estimating OCV

This paper presents a Coulomb counting algorithm using the estimating OCV through a short rest time, such as the traffic signal time. Proposed algorithm could enhance the SOC estimating accuracy through the frequent SOC reset using a greatly short rest time, even though SOC reset error occurs. Also algorithm is implemented for a highly accurate SOC estimation by a SOC error prediction, an improvement of required rest time for SOC reset and a compensation of SOC reset error. The proposed algorithm is verified by experiment using the UDDS profile and it is verified that it could improve the SOC estimation accuracy up to 2.07%.

Comparative analysis of active inrush current limiter for high-voltage DC power supply system

This paper performs analysis and verification of active inrush current limiter (AICL) using the MOSFET for high-voltage DC power supply. To active this, the performance characteristic of AICL is analyzed comparatively with inrush current limiters using inductor, NTC thermistor, and relay, which have been used to protect the devices. And utilized of AICL when is applied to high-voltage DC power supply is considered. In addition, a study on the relationship between the strength of a limited current, settling time and parameter of devices, which are organized AICL is performed. To verify effectiveness of AICL experiment is carried out using actual parameters. Through this study, utilization and reliability of AICL for high-voltage DC power supply is analyzed and evaluated theoretically and experimentally.

DC Appliance Safety Standards Guideline through Comparative Analysis of AC and DC Supplied Home Appliances

This paper provides a safety guideline for DC supplied home appliances through the comparative analysis of existing safety guideline for AC supplied home appliances. For this purpose, a predictive DC home appliance model is suggested and in special international safety standards of AC appliances are also analyzed. Moreover, a DC distribution system is built to verify the validity of the proposed safety guideline. The detailed analyzing process is explained with help of informative experimental results.

A Mixed SOC Estimation Algorithm with High Accuracy in Various Driving Patterns of EVs

In this paper, a mixed algorithm is proposed to overcome the limitations of the conventional algorithms, which cannot be applied in various driving patterns of drivers. The proposed algorithm based on the coulomb counting method is mixed with reset algorithms that consist of the enhanced OCV reset method and the DCIR iterative calculation method. It has many advantages, such as a simple model structure, low computational overload in various profiles, and a low accumulated SOC error through the frequent SOC reset. In addition, the enhanced parameter based on a mathematical analysis of the second-order RC ladder model is calculated and is then applied to all of the methods. The proposed algorithm is verified by experimental results based on a 27-Ah LiPB. It is observed that the SOC RMSE of the proposed algorithm decreases by about 9.16% compared to the coulomb counting method.

A new SOC estimation algorithm without integrated error using DCIR repetitive calculation

In this paper, the State of Charge (SOC) estimation algorithm is proposed using the Direct Current Internal Resistance (DCIR) repetitive calculation, which reflects the renewed Open Circuit Voltage (OCV) in real-time by using the measured DCIR through the constant current injection method. Therefore, it is possible to improve the estimation error because there is no integration error and reset interval. Finally, the performance of the proposed method is evaluated by comparing with the estimated SOC result using the Coulomb-Counting method under the various C-rates experimental conditions. Also, a State of Health (SOH) estimation method using measured DCIR and Extended Kalman filter (EKF) is proposed. The accuracy of estimation method is evaluated by MATLAB simulation results.

High power density SRC for low voltage battery charger in xEV with third harmonic operation technique

In this paper, series resonant converter (SRC) with third harmonic operation (THO) is proposed for low voltage battery (LVB) charger. The proposed converter has unique feature, which is high operation frequency without increasing the switching loss, leading to reducing the inductance and the capacitance for the resonant network and the output filter remarkably. Moreover, the system efficiency can be improved because the switching frequency variation of proposed topology can be minimized compared with the conventional SRC operation.

Adaptive loss reduction charging strategy considering variation of internal impedance of lithium-ion polymer batteries in electric vehicle charging systems

This paper presents a charging strategy to minimize losses in a lithium-ion polymer battery for an electric vehicle. The proposed charging method which considers the variation of battery internal impedance according to state of charge and C-rate significantly reduces charging losses. Experiment results for a cell prove that the proposed charging method reduces loss by 41.9 % compared to a conventional constant-current charging. Moreover, a 3.3 kW prototype on-board charger is built to investigate the entire reduction of losses in an electric vehicle charging system which includes a 12 kWh battery pack considering capacity deviation. Additionally, the feasibility of the proposed charging strategy is examined according to the charger capacity, and it is shown that the effect is enhanced with increasing charger capacity. It is also revealed that the loss reduction due to the proposed strategy is equivalent to an improved efficiency of 3.35% on a 52.8 kW charger with an average efficiency of 94.49%.

A mixed SOC estimation algorithm using enhanced OCV reset and the DCIR iterative calculation reset

In this paper, a mixed algorithm is proposed to improve SOC estimation accuracy for large-capacity Li-ion battery by using advantages of Coulomb counting method, DCIR reset method, and enhanced OCV reset method. Because each method has drawbacks of accumulated SOC error during the operation in EVs, the optimal mixed algorithm is presented. Also, the weighted current value IDC based on the mathematical analysis of the second-order RC ladder model is calculated and then it is applied to methods respectively. The proposed algorithm is verified by the experimental results based on the 27 Ah LiPB. As a result, the SOC RMSE of the proposed algorithm is decreased about 2.22% by compared with the Coulomb counting method.

Hybrid PFC-inverter topology for bidirectional on board charger for range extended electric vehicle

In this paper, a novel power factor correction (PFC)-inverter topology with enhanced performance is proposed for applying to electric vehicles (EVs) and energy storage system (ESS). The proposed topology can be operated as the several modes which include one inverter mode and four types of PFC mode. And operation method is analyzed in detail according to each mode. The feasibility of the proposed topology is experimentally verified with the help of an actual prototype.

Comparative analysis of GaN FET power system for maximizing system benefit

This paper carries out a series of the analysis of the power system using gallium nitride (GaN) FET which has a wide band gap (WBG) characteristics comparing to the conventional silicon (Si) MOSFET-used power system. At first, for the comparison of each semiconductor device, the switching-transient parameter is quantitatively extracted from the released information of GaN FET. And GaN FET model which reflect this dynamic property is configured. By using this model, the performance of GaN FET is analyzed comparing to Si MOSFET. As a result, GaN FET power system, designed by the optimal point suggested in this paper, can reduce the loss by 25.5% and the volume by 78.6% of major components comparing conventional Si MOSFET power system.