Jiuchun Jiang

Evaluation of Acceptable Charging Current of Power Li-Ion Batteries Based on Polarization Characteristics

Battery polarization voltage characteristics of power Li-ion batteries are investigated at different charging rates. The polarization voltage is small and relatively stable in the middle state of charge (SOC) range, whereas at both ends of SOC, the polarization voltage is enlarged and varies rapidly. Meanwhile, there is an approximate linear relationship between polarization voltage and charging rate. Taking polarization time constant into account, an acceptable charging current curve is developed, which prevents charging current from being out of range. This curve takes polarization voltage and charge cutoff voltage as constraints to describe acceptable charging current value at different SOC. Based on this curve, the battery can be charged from 20% SOC to 80% SOC within 33 min. The average polarization and the maximum temperature rise are approximately equivalent to those of 0.5C constant current-constant voltage charging method. The experimental results demonstrate that the proposed charging mode can balance charging speed, charging polarization, and temperature rise.

Butler–Volmer-Equation-Based Electrical Model for High-Power Lithium Titanate Batteries Used in Electric Vehicles

The lithium titanate battery, which uses Li4Ti5O12 (LTO) as its anode instead of graphite, is a promising candidate for fast charging and power assist vehicular applications due to its attractive battery performance in rate characteristics and chemical stability. Unfortunately, commonly used battery models, including a large number of enhanced electrical models, become problematic when describing current-voltage characteristics of lithium titanate batteries. In this paper, a novel Butler-Volmer equation-based electric model is employed to outline unique phenomena induced by changing rates for high-power lithium titanate batteries. The robustness of the proposed model for three types of lithium titanate batteries under varying loading conditions, including galvanostatic test and Federal Urban Dynamic Schedule test, is evaluated and compared against experimental data. The experimental results of three types of lithium titanate batteries with common anode materials but differentiated cathode materials show good agreement with the model estimation results with maximum voltage errors below 2%.

An Optimal Charging Method for Li-Ion Batteries Using a Fuzzy-Control Approach Based on Polarization Properties

Battery charging is growing in importance as it has direct influence on battery performance and safety. This paper develops a generalized online estimation method for a charge-polarization-voltage-based resistance-capacitance ( RC) circuit model to simulate the charging behavior of Li-ion batteries. The effects of charging current, initial state of charge (SOC), initial polarization state, and aging on the charge polarization voltage are quantitatively analyzed in both time and SOC domains. It is demonstrated that the charge polarization voltage is nonlinearly related to these impact factors. In the SOC domain, the change in the charge polarization voltage is also analyzed with the gradient analytical method, and the relations between current, polarization voltage amplitude at the inflection point, and SOC are quantitatively established. This can be used to estimate battery SOC and polarization voltage accurately. A constant-polarization-based fuzzy-control charging method is proposed to adapt charging current acceptance with battery SOC stages. Experimental results demonstrate that the proposed charging method significantly shortens charging time with no obvious temperature rise compared with the traditional constant-current-constant-voltage charging method.

Applications of battery energy storage system (BESS) for energy conversion base in expo 2010

Electric power demand in China increases rapidly due to the thriving economic. As a result of this, the energy storage technologies have been developed and integrated into the electric power system constantly. The research was conducted as part of a demonstrative project commissioned by Shanghai Municipal Electric Power Company. This paper presents an overview of the battery energy storage system in Caoxi substation. Further, an outline of the battery energy storage systems components is stated. The installation includes batteries, power conversion system, battery management system and other auxiliary facilities. The analysis and research based on actual operation data in Caoxi substation are presented. The paper also does research on the comparison of various battery types, and introduces the features of sodium sulfur battery system. Finally, a discussion on the operation modes and applications of battery energy storage system has been made in this paper.

Research and improvement of a zero-voltage zero-current switching full-bridge converter

As is known to all, full-bridge topology is one of the most common circuits in the field of power technology. In pursuit of the efficient and diminutive power equipment all the while, soft-switching technology has been widely applied as an important instrument at present. In this paper, a novel zero-voltage zero-current switching (ZVZCS) full-bridge DC/DC converter is presented to improve the topology of previous circuit. The operation principle of previous topology has been analyzed at first. Since the ZVS effect of the previous converterpsilas leading-leg IGBT cannot be realized very well in the light-load situation, the previous ZVZCS full-bridge converter was optimized. For the purpose of testing and validating the operating principle of improved ZVZCS full-bridge converter and all the analysis, the simulation of this novel ZVZCS full-bridge converter has been carried out with the software PSPICE. With the purpose of charging up the electric vehiclepsilas power storage battery which will be used in 2008 Olympic Games, a prototype (10 kW 130 V/80 A) adopting modified ZVZCS converter is designed and validated by experiment. Finally, the results of the simulation and experiment are provided to verify the principle of this novel ZVZCS converter. At the same time, five conclusions are provided too.

Battery management system for the charge mode of quickly exchanging battery package

In this paper a new kind of battery management system is designed for the charge mode of quickly exchanging battery package. Accounting for this new change mode, we analyze the structure and the function characteristic of battery management system under this mode. After that, we give out some ideas on charge for battery union on the EV bus, charge for battery packages, maintenance for battery packages, recombine battery packages into a new battery union, SOC calibration, parametric recognition in the the exchanging process.

Robust Online State of Charge Estimation of Lithium-Ion Battery Pack Based on Error Sensitivity Analysis

Accurate and reliable state of charge (SOC) estimation is a key enabling technique for large format lithium-ion battery pack due to its vital role in battery safety and effective management. This paper tries to make three contributions to existing literatures through robust algorithms. (1) Observer based SOC estimation error model is established, where the crucial parameters on SOC estimation accuracy are determined by quantitative analysis, being a basis for parameters update. (2) The estimation method for a battery pack in which the inconsistency of cells is taken into consideration is proposed, ensuring all batteries’ SOC ranging from 0 to 1, effectively avoiding the battery overcharged/overdischarged. Online estimation of the parameters is also presented in this paper. (3) The SOC estimation accuracy of the battery pack is verified using the hardware-in-loop simulation platform. The experimental results at various dynamic test conditions, temperatures, and initial SOC difference between two cells demonstrate the efficacy of the proposed method.

Determination of SOC of a Battery Pack Used in Pure Electric Vehicles

Thevenins model having a RC network characterizing the battery polarization is used for SOC determination. Reverse current method is proposed to decrease the polarization elimination time. And the polarization voltage of the battery model is identified using the nonlinear least square technique. A maximum available capacity based SOC determination method considering the SOC limit of each cell for battery pack in series is presented in the paper. Discussed results demonstrate the efficacy of the proposed parameter identification technique and the SOC determination method for PEV application.

SOC Estimation of Ni-MH Battery Pack Based on Approved HPPC Test and EKF Algorithm for HEV

In this paper, Methods of SOC estimation of Extended Kalman Filter (EKF) is studied based on the characteristics of Nickel-Metal Hydride (Ni-MH) battery pack with 120 cells in series and 8Ah capacity for HEV. In the study of EKF-based SOC estimation, the improved Thevenin circuit model is adopted, and a new hybrid pulse power characterization （HPPC） test is designed to identify the model parameters by using piecewise linear regression method. In this way, the precision of the circuit model is improved. In addition, The Kalman gain matrix is optimized for EKF iterative algorithm by two ways: a constant gain is increased taking into account the entire process; a dynamic gain which increases at the beginning of abrupt change and decreases rapidly after abrupt change is set up. The improvement achieves a good tracing prediction.

Robust and Scalable Management of Power Networks in Dual-Source Trolleybus Systems: A Consensus Control Framework

Dual-source trolleybuses powered by onboard battery and grid electricity offer unique advantages in fuel economy, cost reduction, and passenger capacity, which are particularly appealing for public transportation in populated cities. Their mobility and power supply network configurations introduce challenging power management issues on their dedicated supply power grids. To ensure safe, reliable, and efficient operation of trolleybuses, their high-current and dynamic loads must be distributed to the feeders properly and promptly. Based on certain emerging networks of feeders and supply stations for city trolleybus systems, this paper introduces a new framework for current flow balancing based on recently developed weighted-and-constrained consensus control methods to manage the power supply network. Using only neighborhood information exchange among feeder lines in the network, the consensus control can achieve global current balancing with fast convergence to a balanced state, robustness to load perturbations, reconfiguration with feeder addition and deletion, and rebalancing under feeder capacity variation. The methodology is scalable in the sense that system expansion will not substantially increase the control system complexity. The power system configurations of the Beijing dual-source trolleybus system are used for simulation case studies on the new power management methods. Robustness and scalability are demonstrated, together with discussions on the feasibility, flexibility, and implementation issues of the methodology.